Thanks, both of you....

I don't understand this last bit.

"smaller pixels will produce less dark current noise, some sources of which follow a "per unit area" empirical pattern"

It's actually the last bit of the last bit that I don't understand.  :)

The first part of the 'bit' intrigues me.  If there's less dark current noise doesn't that bode well for small site sensors if they can be read multiple times and blended?  (If photons can be cumulated over frames and divided by a lower concordant noise?)

---

Then.  In the focal length/aperture/sensor size relationship, doesn't the front element size also contribute?  Larger area = more light collection.

BJL,
Perhaps no advantage in image merging to reduce photon noise but wouldn't there be some advantage to improve over all S/N? With such small photosites, most of them would have no signal at all with just a single exposure for the highlights.

Ray, now I am confused. Though I believe that claims of DOF/speed advantages for either smaller or larger formats are greatly exagerated, I thought that we were agreed that the lower total dark noise levels (in electrons) is, for the time being, a potential S/N advantage to a smaller sensor.

You realy are passionate about denying any possible advantage to smaller formats, aren't you? One seriously wonders why medium format lost so much ground amongst professionals to the smaller 35mm format if the latter had so little in its favor!

The naive phyics of the possible advantage for a smaller format is that with the same aperture diameter and exposure time, a smaller format sensor gathers the same total amount of light from the same subject (same total signal in photons or electrons) but has less total dark noise (less electrons of noise, due to less total bulk of silicon), which points to a potentially higher overall S/N ratio for a smaller sensor.


On the second point, I thought it was decided in a previous discussion that at a given angular FOV, pixel count, and camera weight, the same shutter speed is needed to freeze camera motion adequately. Since FOV counts, not focal length itself, it should be not 1/f, but 1/(35mm equivalent f).

Before you say that smaller, lighter cameras are thus at a disadvantage: nothing stops one from making a camera of any format as heavy as desired, by adding a battery grip or pure "balast" if needed.

Dropped it? I never had it to drop  :D .

I came acroos the LL forum around the time Michael produced his controversial review of the 3mp D30. I recall all the whingeing on the forum then from people who wanted the greater wide-angle coverage that full frame afforded.

The expectation was that Canon's successor to the D30 would be a 6mp full frame. It was almost guaranteed. Michael made several comments that this was very likely.

I wrote quite a few posts in those days extolling the virtues of the smaller format, but like many I didn't really believe it would be possible to maintain the low noise of the D30 with the smaller pixels that would be required to cram double the number into the same space and I thought Canon would probably cave in to the chorus of demand for full frame.

I was surprised but very pleased that the D60 maintained the same format as the D30, so I bought one.

I've since been rather puzzled by frequent statements from 'experts' that pixel size had already reached the resolution limits of 35mm lenses and that increased pixel density will serve no useful purpose. I've engaged in arguments with people who have tried to put forth the view that the D60 pixel size is simply too small and detrimental to image quality compared with the D30 and that the Canon engineers know this and are pulling a fast one.

My role in this current debate about large sensors versus small is more of a 'devil's advocate' role against the ultimate triumph of the small sensor.

I'm really just trying to get a grasp of the fundamental limitations. Can photonic shot noise, the major noise component in small sensors and perhaps the ultimate barrier to further improvement of image quality, be tackled. I don't know. Do you?

Can dark noise, the major noise component in larger sensors and perhaps the ultimate barrier to image quality, be tackled? Well, there's evidence that it can.

Can the 'small well' photosite of the small sensor capture the range of levels of the larger photosite and therefore deliver the same DR whatever the S/N? Apparently not.

Can technology get around this DR limitation of the small photosite by constructing really deep wells and/or merging several shots in-camera? Maybe.

If the larger format sensors employ similar technology to produce extra deep wells and automatic merging of different exposures in-camera, could the smaller format ever compete, eh!?

Perhaps the ultimate triumphal factor will not directly be S/N or DR but P/P (price-performance ratio)  :D .

Technological development has an effect of 'trickling down'. Of course more people want little things than big things (photo-wise). But humanity as a whole marches on to ever bigger and better.

You lost me there....

Why won't we see a "FZ20" with a wide angle option?  Why not a very wide ceramic short zoom that can be traded out for the monster zoom?

(Perhaps with Samsung is pushing into 15x territory a second lens won't be necessary to shoot everything.  Down the road a 20x 18 - 360.)

Is there a problem building a very wide lens for a small sensor camera?  Or just a lack of market demand?

Ray,

  apparently you have not noticed the trends in mobile phones, portable audio equipment, the cameras that most people have been buying over the last century or more, or almost any other hand-held product. My obervation:

"If it carries them, people want bigger [e.g. SUVs],
if they carry it, people want smaller."

Design in a 'shallow DOF' mode in a small sensor digital.

Immediately after taking the desired shot move the focus point a fixed percent.  (This could happen very quickly as the camera 'knows where it's going'.)  Take a second shot.

Software (initially in computer, later in camera) could calculate relative distance of objects in the frame.  

Then you could choose your favorite brokeh.  (Probably argues for a post-processing approach.  More flexibility.)

(And someone suggested phase shift, but my knowledge of physics is too limited to deal with this solution.)

Well Ray, I get the feeling that you are 'young boomer' or less.  Take a look at us old dogs - Didger who's about boomer + 4 and me, boomer + 2.  We're the point men for this huge population bulge that's working its way toward old.  Both of us are looking for lighter cameras for our travels.  

Maybe you young pups are still willing to set off with several pounds of gear, but lots of others aren't.  Neither do we go shooting with car and driver.  

Didger has just spent several thousand dollars to lighten his load a few pounds.  I'm dreaming of more capable one pound or less cameras that will capture what I'm after.  (In the meantime I'm passing on usable high ISOs and shallow DOF.  It's a price that I am willing to pay.)

Because that software hasn't been written yet doesn't mean that it won't.  And because high DR, small sensor cameras aren't on the shelf at this moment doesn't mean that they won't be.

Market pressure has been for smaller, more portable cameras for a long time.  Olympus made its mark by releasing the first compact 35 mm SLRs.  (I dumped my Pentax for an OM1 soon after they appeared.)

35 mm film won out over MF film, not because the film and developing were so much cheaper.  But because the cameras were smaller.

IMO digital cameras will continue to shrink because the market wants small.  

Now I don't think that the shallow DOF solution is 'blending'.  I suspect that it could be done by 'object identification' and determining the relative distance position of those identified objects by how much the edges become sharper or more diffuse when the focus point is slightly moved.

Will that require some 'chewing power' on the part of the CPU?  Quite possibly so.  But Moore's Law seems to be holding for speed.  Stuff is a-changing.

Reply,

I seriously doubt that either you or I is in a  position to assess the potential of such technologies; if researchers at Standford University say that it has potential, and the technology has already been put into commerical use, I see little reason to worry just because you are cynical!

but I have no idea where you get your 40MHz from. 4x faster than 1/100th of a second is 400Hz, not 40MHz, so you are off by far more than my one zero!.  I repeat that the testing of photosites only needs to be done at a veryeasily attainable frequency of about 10,000 times per second or less.

By the way, the version that I have heard of does a local analog to digital conversion on the chip at each site, applies an adjustment for the different exposure time at different sites to that digital value while still "on site" (probably just a bit shift for each factor of two difference in exposure time), so that the final data read off the sensor after the exposure is finished is already digital, and so immune to any further noise sources.


As to your absurd taunt about 4/3 format, I should not stoop to this nonsensical DPReview forums style rhetoric of "my brand currently sells better than your brand, therefore it and/or its format size are inherently and permanently superior".

Alright, I will stoop a bit, just for fun.

a) The size difference between 4/3 and say Canon's 1.6x is so small that the broad factors I am discussing have so little effect; they are probably drowned by other variations between product lines: it is about 10% to 20% linear, 20% to 40% in area, or less than a half stop.

The jumps in format size that are big enough to have a clear cut effect are ones between levels like
- digicam, up to 2/3"
- the new DSLR formats as a whole, everything from 4/3 to DX
- 35mm
- 645

A huge array of other factors are in play when comparing Olympus to other DSLR makers, most obviously that back in the 35m film SLR era, Olympus had become a far smaller player than Canon and Nikon, or even Pentax and Minolta, with no established auto-focus lens system and a tiny SLR user base.

c) A far more interesting comparison is to Pentax and Konica-Minolta, who were closer to the size of Olympus in the 35mm film SLR market than were Canon and Nikon, though still substantially bigger. The Olympus E system is reportedly easily outselling both Pentax and Konica-Minolta DSLRs combined, and also outselling both Fuji and Kodak DSLRs, and possibly about matching or surpassing all those brands combined for unit sales volume.

So in fact, the E system has overtaken a number of competitors including several bigger companies who were in the DSLR market earlier.

d) As far as I can tell, Olympus E system models also easily outsell Canon's 35mm format models, in both unit volume and revenues. (Perhaps you will complain that this is due to huge price differences; but once you raise current sales volume as an argument, price is a legitimate factor in comparing the viability and prospects of different formats.)
The figures I have read in official statements from Olympus and Canon are shipments of about 40,000 units per month for the E system in the early months of 2005, versus a reported production level of 2,000 units per month, first for the original 1Ds and then for the 1Ds Mark II.

From other sales figures, 4/3 probably outsells all digital offerings in all formats 35mm and larger.

e) If instead you compare Canon's own sales in different formats, or 35mm DSLR as a whole to smaller format DSLR sales as a whole, then by your flawed reasoning, the glaring conclusion would be that it is 35mm format has totally failed to "overtake anyone" in the DSLR market place, despite the backing of the industry leader Canon. Instead 35mm DSLRs are stuck with a very small and shrinking share of total DSLR sales and revenues. As far as I can tell, 35mm format digital even has a smaller total sales volume than medium format had in the era of film.

I was certainly beginning to get that impression, BJL   , but thanks for clarifying your stance on this.

If the sampling technology you've mentioned really is practicable and would not require unrealistic amounts of computing power and/or significant delays during the exposure whilst photosites discharge and reset; if it really is technically easier and more economical to manufacture a truly diffraction limited f2, small image circle lens, than it is a diffraction limited f8 35mm format lens; then I think there could be justification for claiming the smaller format superior on balance. But not of course in every respect. I don't see how technology could ever hope to 'mimic' the combination of speed and image quality of an 85/1.2 35mm format lens, using a 2/3rds format, unless it becomes possible to make an F0.3 lens at some time in the future. Creating a shallow DoF could be done in software, so the bottom line is really one of speed in favour of the larger format and ultimately resolution if at some point, for example, it becomes possible to make a diffraction limited F4 lens for say, 35mm but impossible to make the equivalent diffraction limited F1 lens for a 2/3rds format.

Actually, I'd be very interested in an affordable 2/3rds format camera with detachable 400mm f2 diffraction limited lens and image stabilisation. Wow! That would be one superior camera.

This idea of 'the best camera for the job' is interesting. It really highlights what an expensive hobby, or even free-lance profession, photography can be. A camera for each situation. This is getting very specialised and professional.

Those who are well-heeled can of course afford that variety of equipment. I cannot. I'm a generalist rather than a specialist and I want a camera system to be as versatile as possible, which is why I (and clearly many others) have opted for the interchangeable lens system of a medium format camera... er! not medium format as in the old MF 6x7cm etc, but middle of the range from 4mmx5mm to 36x48mm.

We all tend to make compromises between absolute image quality, convenience of operation and portability, depending on our priorities.

I haven't yet got to the stage of preferring a 2/3rds format camera on long walks because it's lighter than my 20D plus a couple of lenses. But I might eventually  :D .

I am amazed to see both of you interested in an idea I have had for a while: a fully professional level Canon DSLR in EF-S format, for situations where "agility" and the longer telephoto reach of any given lens through using smaller pixels is an advantage. The long awaited EOS-3D?

Can anyone else see this being an interesting option for some sports and wildlife, as a complement to the 24x36mm format 1Ds series?


P. S. Ray, it sounds like your MF gear is meeting the same fate as my film scanner!

Well, I've never come across MTF charts at 50 lp/mm, but for what it's worth, the best performance of the 70-200/f4 at 135mm and f8 is approx. 67% (averaging tangential and radial), and the best performance of the 100-400 at 180mm and f8 is 57%. (Photodo results)

Do we drop down about 20% for 50 lp/mm or more?

Well, Bob, I think you're straying off the point here (or the point that this thread has evolved to). I've already had a discussion with Didger that lighter is better for backpacking purposes, so forgive me if I don't want to get into that argument again  :D .

I merely make the point that during the past 5 or 6 years, despite the apparent take-over, plethora and ubiquity of the small and very small digicam, the rate of increase in absolute image quality of these small devices seems no greater than that of the larger formats. All formats are getting better, year by year.

The star performer so far this year has undoubtedly been the Nikon D2X, but I don't necessarily think the success of this camera will knock FF 35mm out of the market.

I'd like to ask this question in a calmer, more helpful forum than where the issue originated.  :)

Here's a C&P from a post...
--------
Size of FZ20 sensor = 5.76*4.29 = 24.7104mm2

Size of 350D sensor = 337.5mm2

Ratio: 13.7:1

f-stop multiplier = sqrt(13.7) = 3.70

Hence a lens for the 350D only needs to be 2.8*3.7 = f10.36 to be effectively as bright as the FZ20.

--------

First, true?  (And a link to a simple explanation would be appreciated.)

Second, if true then how does one compare the capability of one type camera to another?

First a warning, the total "dark noise" in each pixel comes from a mixture of at least three types of dark current in the sensor photosites plus noise picked up later in the process, as the charge is moved out of the photosites, converted from a charge to a voltage, amplified, and fed through an analog to digital converter. There is a detailed discussion of this in the Kodak technical report http://www.kodak.com/global....ces.pdf
The only thing I am fairly sure of is that increasing photosite size will tend to somewhat increase the total dark noise, counted in electrons; how fast it increases is probably slower than proportional to area.

That complicates your interesting question about blending multiple frames from a smaller sensor, which is somewhat related to several technologies currently being used in surveillance video cameras to get great dynamic range out of small photosites. I think you can rest assured that lots of ideas like yours are being worked on; manufacturers love the cost advantages of squeezing ever better performance out of ever smaller sensors. (For example, have you heard about the latest sensor from Sharp, with more pixels than the previous 8MP, 2/3" format champion and in the smaller 1/1.8" format, meaning 2.2 micron pixels? See http://www.dpreview.com/news/0410/04102601sharp8mp.asp)


Suppose a smaller sensor and pixels are 1/4th the size of a larger one. When you push exposures time to as long as they can go within the limits of well capacity signal (electron count), the total signal that the larger sensor can get in a single frame would require blending four frames from the smaller sensor. Due to the "root mean square" way that random noise sources like dark noise combine, this would give twice as much noise as a single frame, not four times as much.  So if all the dark noise varies in proportion to pixel area, it is 1/4 as much in each frame for the smaller sensor and so still only half as much in the blended image.

But as I said above, the overall scaling between photosite size and total dark noise is not clear, so the "winner" here is not clear either.


Front element size is indeed the key factor in light collection rate, and you are roughly keeping it constant when you scale the aperture ratio with the square root of sensor area, since the focal length also scales with the square root of sensor area (linear sensor size) to maintain the same FOV.

Ray, completely new text, I misunderstood your post! Then again, maybe you misunderstood my point too, or maybe it is a matter of language: what you call improving overall S/N ratio, I think of as improved dynamic range.

Yes, so long as sensor designs limit the maximum exposure (minimum Exposure Index or minimum ISO speed) due to limited highlight headroom, blending can improve shadow noise levels by allowing the use of a longer exposure for the shadows, blended with a shorter one for the highlights. Still true even if photon shot noise were the only noise source.

I start to imagine cameras that automate sequencing of frame for both exposure level blending and the focus distance blending described in another recent thread. For fans of ready to use JPEGs cameras could even do such blending themselves if processing power increases enough. (Outputting in JPEG2000, which seems to allow bit depth greater than 8.)

Is that what I've been doing  :D . I thought I was arguing that the fast lens/greatDoF/fast shutter speed combination of the smaller format is an illusory advantage.

But now that you've mentioned it, there's another factor related to this matter which perhaps you can shed some light on. How far does the 1/FL rule of thumb extend with the shorter lenses?

There were many situations in Italy where photographing art works (in the Vatican Museum for example) was only permitted without flash or tripod. I was constantly faced with the dilemma of using 1/15th at 15mm and ISO 800 or 1/30th at 15mm and ISO 1600. (Not really much of a dilemma. A lot of the time I'd take a shot at each setting.) But I found that I was usually able to get a reasonably sharp image at 1/15th and 15mm, but not at 1/15th and 30mm.

Can we say that the 1/FL rule should still apply to the 4 and 5mm lenses of small format cameras, or does it completely break down due to the difficulty of holding a small, light object steady?

Ray,

  perhaps I should put it this way. You and many others seem committed to the idea that a smaller format has little or no advantage in image quality in any situation, but perhaps the more relevant question is the other way around:

When does a smaller format has distinct disadvantages in image quality, enough to offset its clear natural advantages? [Added:there certainly are cases where such disadvantages exist and create an advantage for a larger format!]

About these natural advantages, something should be clear, since it has been going on at least since the invention of the enlarger started pushing formats smaller than those needed for contact printing. Higher sensor/film resolution (e.g. smaller photosites), and the smaller formats and shorter focal length lenses allowed by that higher resolution, generally lead to reduced size, weight, and cost. This in turn can increase the chances of being in the right place at the right time with the right equipment for the shot, thus increasing the quality of some images.

A tie on basic image quality is an effective image quality win for a smaller format.

Indeed this is driving a very strong overall trend towards using smaller formats in digital than were used in similar situations with film. (Latest victim; all but one of the Hasselblad 6x6 format cameras have joined most Bronica and Fuji MF cameras in the museum.) While we debate theory, sensor design efforts are overwhelmingly focused on reducing photosite sizeand enablig wider use of smaller formats. I wonder if some people are so out of touch with reality that they still have hopes for a low priced 6MP 35mm format sensor? (Not you Ray; I am sure you have dropped that idea by now!)

I think that one of the revolutions we'll see in future cameras will be in optics and packaging.

I imagine flexible/semi-liquid lens elements, or better collapsible elements, all inspired by flexible, composite mirrors used in astrophotography.

Optical interferometry may also be usefully miniaturized.

My vision, if I may call it that, is a collapsible SLR-like camera (SLR-like in how you look through the lens, rather than in physical dimensions) that can fit in my pocket, yet when I want to take a picture, it expands to a sensible size and focal length for the shot I want to take.

There'd be no interexchangable lens system, because the built-in lens system would adapt its properties to the momentary requirements.  The sensor could be made bigger than 35mm, if almost everything else can be collapsed into something very and compact.  Professionals would probably have access to bigger models capable of giving better optics, as usual.

A major challenge would be to make the expansion and collapse of the camera user friendly and safe, since quite a few bits and pieces would probably be both sharp and delicate.

I wish I could say "as seen in the SF movie ####", but I don't know about any SF movie depicting something like this.  :)

This all requires technology that we're on the verge of developing or minituarizing, and maybe we'll see something incorporating ideas like these in 10 or 20 years.

As I have said before, methods already exist to essentially eliminate the effects of well capacity limits; for example, reading out each well as it approaches being full. Most of your arguments crumble once that is achieved, because it is not possible for a larger format to offer better than the UNLIMITED highlight headroom and dynamic range of a smaller one.

It is then enough for the S/N ratio of a nearly full, small phototsite to be good enough. Kodak says that one get excellent image quality once the S/N ratio at a pixel is 40:1, so that a well capacity of about 2000 is plenty, evn allowng for some dark noise. That is less than 10% of teh smallest DSLR well capacity that I know of, and even slightly sub-2 micron pixels should be able to do that.


Your triumphant responses from large format come down to only the fact that the SAME can be achieved as in a smaller format, but using bigger, more expensive sensors and longer lenses. It is lucky for larger formats that there are better arguments, like the likelihood that smaller formats are at some point limited to lower maximum aperture diameters and thus lower maximum shutter speeds.

Because how do you expect larger foramts to compete when your campaign slogan for them seems to come down to "we're bigger and more expensive, but otherwise just as good?"

Speed is one thing that almost certainly is lost when formats gets too small. We cannot divorce from the ultimate limits on trade-offs between shutter speed, resolution, and noise levels that is set by how fast we can gather light from the subject. As an example, to give our midtone pixels Kodak's "excellent" S/N ratio of 40:1, we need 1600 photons detected at mid-tone pixels, and combined with the currently fashionable 8MP, that needs about 12.8 billion photons total, for any format.

Light gathering rate is limited by the area of the lens opening over which light from the subject is intercepted, and thus by the effective aperture diameter. Whether 35mm format with f=80mm f/8 or 2/3" format with f=8mm, f/2, you have aperture diameter of 10mm, and can gather light at about the same rate.

Thus the speed possible in 35mm with f=80mm, f/2 (40mm aperture diameter) would need that 2/3" format, 10mm lens opened up to f/0.25. I have not seen absolute proof, but I strongly suspect that this cannot be done with good image quality.

I happen to fall at about the 4/3 format level. A limit of f/2 there matches a limit of f/4 in 35mm format digital, and I have little or no need for the combination of less that "f/4 equivalent DOF" and higher shutter speed that a larger format might offer.

Okay! On reflection, I've decided there's a flaw in my reasoning. (Nothing to do with the 1/FL rule though Jonathan).

Since the physical aperture at f10 on the big camera is the same size as f1 on the small camera, there's no major speed advantage at f10 except for maybe a difference in optimal ISO settings. The only advantages I can see are at big apertures where there's less DoF.

The only software I know that does this sort of thing requires many shots at different focussing distances. Any software that could reconstruct full detail from two out-of-focus objects is beyond my comprehension.

If you wanted to take full advantage of the potentially greater resolution of the larger format at large diffraction-limited apertures like f2.8 without sacrificing DoF, then I suspect you'd have to trade off speed for the greater DoF, ie. 10 to 100 shots of focus autobracketing, digitally blended with massive computing power. Seems to me that's very analogous to the method BJL proposed for extending the DR of the small format.

Heh, heh, yeah; you never know who might be lurking where when. :laugh:  
Actually, weight was the issue that made me look into the D2X, but I was only hoping that I'd get more or less the same quality as 1ds.  Now that I've taken a few hundred "real life" shots I'm realizing that I might have done it even totally apart from the weight issue.  I'll be posting a few pics after a while to illustrate particular points related to the importance of more DOF and much less high ISO noise, and being able to use a few zooms without quality compromise, and the real life image quality improvement that comes with better ergonomics and display visibility under various lighting conditions.

Now I just hope that the D3X with twice the DR comes along before my 3 year extended warranty for the D2X expires.  That camera is getting USED.  I've never had a more totally happening toy/gadget/tool in my life and I take shelter behind the vast credibility and respect of Thom Hogan to justify my "excessive" enthusiasm.

BJL,
You're quite right on the first point. I haven't even read of the research you are talking about so it's purely idle speculation on my part.

On the second point, I'm not cynical, I'm skeptical, and for good reason. There are quite a few major innovations in this area that occasionally crop up, cause much excitement and appear to herald the way of the future: the Foveon sensor, for example, Fuji's SR sensor and then the new Olympus group's 4/3rds sensor with newly designed Zuiko lenses which by all accounts are excellent lenses, probably a cut above the equivalent Canon lenses.

But for some reason, the promise of these new technologies is not being fulfilled or at best is developing slowly and what on paper seems a major break-through turns out to be just an incremental improvement.



Surely you must have realised I wasn't referring to sales? The entire tone of this thread is about comparative performance of image quality. Of course I meant that you must be disappointed the Olympus 4/3rds system has not yet overtaken in performance and image quality the next format up in size, the Canon 20D.

Ray,

   here is my overall perception. The best format for one's purposes is one that is just big enough to offer
a) good performance out to one's personal needs and limits for shallow DOF, high shutter speed/low light performance, and size and weight of lenses (which all relates to limits on how big the "big glass" needs to get, in terms of maximum aperture diameter and thus front element size).
adequate pixel count (how small can photosites get?)
c) adequate dynamic range (which might well cease to be a size limit at all)
Going bigger than that just adds "excess capacity" such as larger than necessary electron wells leading to more dark noise.

As with your example: lovers of using f=85mm @ f/1.2 of f/1.4 will probably only ever have one best choice of format: "24x36". Those of us whose DOF goals almost always limit f-stop choice to the range from f/4 up in 24x36mm are probably better served by one of the smaller current DSLR formats, but with 2/3" still to limiting.

I absolutely agree with the 'portability' issue.  I was so tired of the weight of SLRs and multiple lenses that I was ready to either quit shooting (pass on 100% of the shots) when I traveled or take a rangefinder (pass on many of the distance shots).

Then digital became an option.  And walking around with a one pound monster zoom is a joy.

I'm a happy puppy.  But I'm always looking for something even better.  

So Canon comes out with a half-frame, what?  14 megs to beat Nikon?

And that drives the 1DsMkIII to say 20+ megs?

Man, this is going to be interesting.   ::

At the risk of getting shot down in flames for not knowing what I'm talking about, I would say you are essentially correct if, by brightness, you mean the f10.35 lens on the 350D will let in the same amount of light as the f2.8 lens on the FZ20, per unit of time of course. In other words, the physical aperture openings will have the same diameter in each case.

However, since the 350D sensor is around 14x the area of the FZ20 sensor, it will require 14x the amount of light (number of photons) for correct exposure which is approximately what f10.35 on the 350D will produce by requiring an exposure 14x longer.

A fascinating flow on from these basic principles is the possibility of producing ever smaller and smaller sensors of higher pixel density that can match the resolution of much larger sensors using very small lenses with a small f stop. (Well, fascinating for me.)

Where will it end? Will Didger be able to reduce his camera gear weight by yet another few lbs and still get marginally better image quality than the D2X gives him?

Can we break or circumvent those (apparently) immutable laws of physics such as diffraction limitation in lenses, photonic shot noise which has an increasingly more significant effect the smaller the sensor gets, and ultimately produce photosites no bigger than the wavelength of light?

As an after thought, what we might soon get is an ultra lightweight pin-hole camera that produces razor sharp images instead of the very blurry images we associate with pin-hole cameras. The dynamic range would probably be miserably low and such a camera might only be useful for very static subjects where multiple shots could be taken at different exposures and blended with PS CS2's new HDR feature.

What I find interesting here is that dark noise is subject to technological strategies for improvement even if it requires a certain degree of internal cooling (which wouldn't necessarily be difficult with a really tiny camera housed in a much larger body so one can hold the thing).

Photonic shot noise and diffraction limitations seem to be the ultimate barriers to small cameras producing high quality, high resolution images.

I take the point that averaged multiple exposures might reduce the randomness effect of misbehaving photons (you can see I'm not very technical) but I suspect not by much.

Photon noise is proportional to the sqrt of the number of photons impinging upon the photosite. Ie., if the photosite receives 100 photons, noise is 10 photons, or 10% of the signal. If 1000 photons are received by the photosite, noise is represented by a mere 32 photons, about 3.2% of the signal.

Is this a limiting factor as draconian as lens diffraction limitations?

I made the comment that maybe soon we'd have an ultra-small camera capable of matching the DoF of a pinhole camera but with razor sharp images. I can't really see it unless these basic laws of Physics are repealed. (Perhaps the new Pope can do that. Oops! I apologise in advance in case anyone deeply religious is reading this  :) ).

To clarify the problem, I designed an imaginary small camera to compare with FF 35mm in terms of DoF and resolution. Using the wavelength of red light as the limiting factor for pixel size, and allowing for the usual discrepancy between pixel pitch and pixel size, I used a 1 micron pixel pitch on a 4.5x3mm sensor (keeping the same aspect ratio as 35mm).

Such a sensor would have 15MP and a standard lens, equal to the diagonal of the sensor, would be about 5.4mm in focal length.

To get the same DoF and resolution of a 35mm camera at f8, we'd need a diffraction limited f1 lens. (Not possible now maybe, but with the help of nanotechnology and improved materials, maybe sometime.)

This would clearly be an amazing camera for any subject that requires a reasonable DoF, but with one serious limitation; dynamic range. I can only guess what that might be; 1 stop of undegraded DR described as 3 or 4 stops by the advertisers of such a product?

Let's assume such a camera has just 1 stop of 'clean' DR. To get a DR of 8 stops, we need to blend 8 exposures, the shortest of which for the highlights (which at F1) might be around 1/25,000th of a second on a sunny day. We progressively halve that shutter speed for each of the 7 remaining stops till we reach 1/200th sec for the deep shadows. Bingo! We've got the full DR of a modern DSLR, and more perhaps.

But what about DoF? Well I'm afraid we're stuck with the limitations of diffraction. With such a camera the hyperfocal distance is around 24ft whether it's a 4.5x3mm sensor at 5.4/F1 or a 36x24mm sensor at 43/f8.

Supposing we want a really great DoF comparable to that of a pinhole camera but at the same time sharp. Perhaps we could reduce the aperture opening from F1 to f8 on our miniature camera.

The DoF calculator I've been using at http://www.dofmaster.com/dofjs.html tells me that such a camera I've designed, at f8, will produce a sharp image from 1.5ft to infinity (CoC 0.004 proportional to the program's fixed CoC of 0.03mm for 35mm format). Whatever CoC standard is chosen, the relevant multiplying factor is 8 and the results are the same.

Okay! The assumption is, the lens at f8 can transmit that resolution. Well, of course it simple can't because of diffraction. The sensor in my designed camera has at most a theoretical resolution of 500 lp/mm, but a paractical resolution of maybe 400 lp/mm with a diffraction limited F1 lens. (Guess work of course).

Any image at f8 on such a camera would be no sharper than a 35mm shot at f64.

Clearly there is a lower limit on pixel size, somewhere between 1.8 microns (already achieved) and about 0.6 microns (longest visible wavelengths). So I am sure that it will make you happy to know that a small format like 2/3" is at the fundamental disadvantage of never possibly going beyond resolution of about 5,000 line pairs per picture height, or about 140MP. Darn, camera phones will probably never even get to 50MP!

There seem to be lots of other more immediate practical reasons why formats significantly smaller than the smallest current DSLR format will alway be at significant disadvantages. Some days, when I am in an unusually humble mood, I even believe that the engineers at companies like Kodak, Olympus, Nikon, Sony and Canon know their jobs far better than we do, so that their choices of the new digital SLR formats, from 4/3" to DX, are rationally based on a good understanding of future technical possibilities and limitations, and are not stupid or shortsighted stop-gap measures.


About electron well capacity and/or dynamic range for very small photosites, it is not clear that there is any fundamental limit, even without blending. Let me mention a technical possibility that I have read about recently, and remind you of one that I mentioned some time ago.

The new idea is using "nanotechnology" to build photosites that are tall thin towers, literally increasing "well depth", and in practical terms greatly increasing the electron capacity of very closely spaced photosites, giving them very large dynamic range. However, this increases the total "bulk" of each photosite, and so increases at least some sources of dark current, so it is not clear how performance will compare to "wider, shallower" photosites with the same well capacity.

The previously mentioned idea is photosites that are checked repeatedly during an exposure, with the more brightly lit ones read out as they approach being full. Thus highlights get read quickly, shadows more slowly, with the different exposure times for different pixels being taken into account in the final digital conversion of course. It is like taking a sequence of exposures of different durations, but all starting simultaneously.

This might also have a slight bonus over a conventional single exposure using a sensor of higher dynamic range: the better lit parts are exposed more briefly, so motion blur from the longer exposure time needed to hold the shadows does not effect the highlights as much. A slight win over a conventional exposure where highlights are also exposure for the full time.


Finally, I do not see why you keep working so hard to argue that the potential noise advantage of smaller photosites wil become an illusion at some point, because no-one seems to be disagreeing lately. Any advantage or disadvantage will go away if and when dark noise is reduced to an insignificant level, at least when comparing images made with apertures chosen for equal DOF (equal effective aperture diameter). Only until then is smaller potentially "quieter".

Ray,

  firstly, your example of a tiny 4.5x3mm sensor is not of much practical relevance; I think it would make much more sense to stay with the current DSLR formats from 18x13.5 up, or at smallest 2 micron pixel pitch in 2/3" foramt. Indeed photosites about this small are on the market now (2.2 microns in an 8MP 1/1.8" (Sharp?) sensor in the new Ricoh Caplio GX8) or coming soon (under 2 microns in a Matsushita CMOS sensor for mobile phones.)

Secondly, your guess of 1 stop DR for 1 micron pixels is absurdly pessimistic. Current sensors can have well capacities of over 1,000 electrons per square micron, while good shadow performace is got at about 10:1 local S/N or less, needing about 100 photons if dark noise is low enough that shot noise is the main factor (as it would be with such tiny photosites.) From 100 to 1000 is a bit over three stops, and that is a pessimistic estimate of the possibilities. The advertised "engineer's DR" figure could probably be more like 8 stops, since the floor noise level would likely be no more than 4 electrons, giving at least 1000:4 or 250, roughly 2^8.

At 2/3" format and 2 microns, I am fairly sure that the five or size stops needed for scenes of normal subject brightness range will be available as base ISO speed. Then blending just two exposures has the potential for handling great subject brightness range.


Thirdly, and yet again about diffraction limitation: at those equivalent aperture ratios (same effective aperture diameter), diffraction effects are exactly equivalent! f/1 in your tiny format, f/2 in 2/3" format, f/4 in 4/3 and f/8 in 35mm format give exactly the same angular spreading of light by diffraction, since it is diameter of the small hole that light is passing through that determines this. So the diffraction spots with the smaller formats are smaller in exactly the same proportion as the sensor and pixels are smaller, and the same size on same sized prints.

BJL,
A tie or a win for the smaller photosite? I can't quite follow your reasoning.

Let's consider that a small format (say 2/3rds) through continued technological development could reach a stage of providing adequate resolution for razor sharp poster size prints with superb dynamic range that for all purposes are essentially noiseless.

Isn't this as fanciful science fiction as 'beam me up Scotty'?

At what ISO would this small camera that had conquered all DR constraints operate? ISO 3200? ISO 6400? Maybe even ISO 12800?

Anyone who's tried to take photos in the Vatican Museum without tripod or flash knows that a camera capable of noise-free images at ISO 12,800 would be very handy.

Will your small camera ever be able to do that?

Seems to me the bottom line is this: Whatever remarkable achievements in signal-to-noise, dynamic range and resolution the small-camera designers can pull off, the large-camera designers can do better. If the 2/3rds size sensor eventually gets to 50MP and produces essentially noise-free images at ISO 400 with a dynamic range of 12 stops, then the larger format sensor, through application of a similar degree of technological development, could hypothetically without breaking the laws of physics, reach 200mp and produce essentially noise-free images at ISO 3200.

It's not all to do with signal-to-noise. Two different sized photosites could have the same S/N but one could have a hugely greater dynamic range, and that makes all the difference.

Let me try to make this a little clearer. Let's do a couple of hypothetical but relationally similar examples; my diffraction limited 5.4/F1/4.5x3mm 1 micron 12mp sensor compared with 35mm full frame 43mm/f8/12mp. Resolution and DoF the same in both cases.

Both sensors have taken noise reduction techniques to the limits of the laws of physics, which means that photonic shot noise is the only noise. (Okay! Nothing's perfect! Give or take a couple of electrons. Let's not pixel peep here).

Our 1 micron photosite can hold 1000 electrons, 33 of which are noise. Our 8 micron photosite can hold 64,000 electrons, full well, only 264 of which are noise (is that the right figure - I haven't got my calculator?). We've already got a huge dynamic range advantage of the bigger sensor as well as S/N advantage.

The smaller sensor says, 'Hey! We can build a really deep well that can hold 64,000 electrons and we won't even lose much shutter speed advantage of big brother because we've got F1'. Oops! We've now got more dark noise. Blast it! Never mind! BJL has discovered a way of eliminating all dark noise.

The big sensor says, 'We're aware of BJL's tricks. We've decrypted his 'dark noise removal algorithm' and we can now create a well that holds 512,000 electrons with an S/N that's even less than small sensor.

Small sensor responds.' No worries! We'll blend multiple exposures'. Big sensor retaliates, "So what! We've already done that. We're into the billions of photons old chap. We use huge lenses diffraction limited at f2, schleimflug tilt effects and DoF bracketing. Who kidded you that you could ever compete?

I'm not sure but what when it comes to digital camera development things don't trickle up.

And 'bigger and better' got a divorce a long time ago.  

I'll bet there's some minimal size at which there's little market pressure to go smaller, but until we reach that point the movement is likely to be toward smaller packages.  A smaller camera is a camera that's more likely to be carried, thus more likely to bring home the bacon.

I'm pretty convinced (via the previous discussion) that the DR problem is solvable.  DOF is next.  (And if even a simpleton such as me has an idea or two....)  


(And how come we aren't hearing anything about ceramic lenses?)

I am not ruling out quite good cameras in smaller formats like the now fashionable 1/1.8". For example, I like the Olympus C-7070 with its 27mm equivalent or better wide angle coverage.

But there do seem to be lower limits on attainable f-stops, not much below f/2 for zooms, which would limit formats 2/3" and smaller to the DOF options and light gathering speed of not much under f/8 in 35mm format. Even 4/3 seems limited to about "f/4 equivalent zooms", which seems borderline for a flexible, general purpose system.

Clearly, many digicam users live happily with "f/8 equivalent", including some quite serious photographers who simply have little need for shallower DOF or better high shutter speed/low light performance. But it seems too much of restriction for a flexible, interchangable lens system. Especially since the current smaller DSLR formats are already offering such low prices and small sizes.

The 1/F rule applies to the 35mm equivalent focal length, or (actual focal length) * (full-frame crop factor). So a 4mm lens becomes a 20mm or whatever for the purpose of estimating the maximum practical exposure time interval as well as describing FOV.

BJL,
It would certainly seem like that. You probably read more industry analysis reports than I do. Companies in general are obliged to make a profit and it's difficult to make a profit selling products for which there's little demand at a price point which few are interested in. (Unless one has a lucrative contract with the US government ).

However, when I cast my mind back to the days of the Nikon D1 (and shortly later the Canon D30), I do not see any performance catch-up of the small format. At the top end, we seem to have gone from computer tethered 6MP MF backs with 35mm size sensors to larger format, untethered 25MP backs. In the middle, we've gone from slow 3MP APS-C cameras to much faster 8MP APS-C cameras with significantly less noise at high ISO. At the low end, we've also progressed from noisy and slow, 2 & 3MP P&S cameras to the likes of the 8MP Sony F828 and KM-A200.

Is there not always a price premium for miniaturisation when quality is not to be sacrificed? I don't see any examples of miniature cameras equalling the performance of their larger brothers at any price. Just a few days ago I was looking at a friend's brand new K-Minolta 8mp A200, an upgrade from his Canon G4. Browsing through the review he'd downloaded, I noticed that after a burst of 5 frames in RAW mode the KM A200 leaves one waiting 45 seconds before one can take another shot. 45 seconds? Ridiculous!

The technology you are proposing for the small camera (continuous sampling of each photosite as it fills and discharges) would seem to require fairly massive computing power. It might eventually be cheaper to manufacture a larger camera to accommodate all that extensive processing power. Desktop computers are considerably cheaper than laptops at a comparable performance.

Ray,
   the frequent checking of photosites for fullness is a "parallel process", done independently and simulteanously at each photosite, and at a rate of maybe 10,000 times per second or less. In the modern jargon of computing speed, about 0.000001GHz: an absolute snail's pace, and not requiring any processing power beyond that in the sensor itself.

About progress in different sizes, I am mainly interested in the range of DSLR's from mainstream makers, not tiny digicams or the small and shrinking market for format larger than 35mm. This partly because I suspect that DSLR makers are likely now locked into formats by the current array of lens formats from 35mm down to 4/3.

Comparison to performance weaknesses of far less expensive compact digicams aimed at quite different customers is fairly irrelevant to bottom line questions like "which choice will give me the best performance for a given price?"

In almost three years since Canon and Kodak first anounced their 35mm format DSLRs, we have seen just one substantially new 35mm format sensor, one sensor revision, and one sensor and product line abandoned (the Contax DSLR). to ne sensors if you count Canon's 1.3x for the 1DMkI. This has moved the maximum pixel count from 13.5MP to 16.5MP, with little change in prices, and with just two camera makers participating.

In the same period, seven DSLR makers and six sensor makers have offered at least half a dozen new sensors, several updates of existing sensors, considerably more new models, rapidly dropping prices, pixel counts increases from 6MP to 8MP and then 12.4MP. (By the way, they have also repeatedly confounded the pessimists and cynics by reducing noise levels along with those increases in resolution and reductions in pixel size.) The tempo seems far faster at the smaller end of the DSLR world.

By the way, at the next size level down, the 2/3" digicam sensor format and "prosumer digicams" seem to be in retreat or at least stagnation, as if the entry level DSLRs are taking away market share. So in that battle, the larger format seems to be winning; it is not all one way or the other. Unless 2/3" is just losing out to 1/1.8".

P. S. Perhaps I should qualify my speculation about 35mm format digital possibly falling off the R&D pace. 35mm digital is in a better situation than MF film for sharing of technology with smaller formats, through being backed by one major mainstream camera maker, and a fair degree of overlap in lenses. Better than than situation at Hasselblad, Rollei, Bronica, and Mamiya, and even Pentax with its mostly separate lens systems.

OK, let's turn up the heat under the 'big boy' cameras a bit more.

Fuji just released a compact digital with 'usable' ISO 1600.  

F10Zoom Review

Looks like rapid sensor sweeping won't be necessary to solve the small camera - high ISO problem.  

(And it might explain why we haven't seen a Fuji monster zoom with IS.)

Bob,

  that is a reasonable "optimization" approach, to which I will just add one thing: the inability to have the gear with you at the right place and time prevents some photos from being taken. So even your "special built MF jobbie"  will not in practice do it all.

The gear that allows me to get the greatest number of good results is not the same as the gear that would give slightly better image quality except that it is sitting back at home or in the car because I do not have a pack mule. Another reason for having cameras in several formats: even Ansel Adams used a miniature format camera (Contax 35mm) at times.

BJL,
You're right, I did pick up a couple of used MF film cameras and a number of lenses before getting my first digital camera, the D60. The previous owners were no doubt professionals who were dumping the gear because of a move to digital. I thought the price at the time was really good. Couldn't resist  :D .

However, having previously switched from Minolta to Canon a short time earlier, there was no significant advantage to either format regarding focal length for me at the time. My MF lenses range from 50mm to 300mm in primes; my Canon EOS lenses from 28-135 (zoom), 90mm TS-E and later a Sigma 20mm.

The choice of MF gear in any situation was really a trade-off between convenience factors and absolute image quality. The RB67 (nicknamed 'the tank') was versatile in its range of lenses (4 primes from 50mm to 300mm), but weighed a tonne. The Fuji GSW690 lll (6x9cm) has a fixed 65mm lens; the body's made of carbon fibre so it's very light and is very backpackable but not at all versatile in its range of lenses.

I keep telling myself I must use this MF gear more often, but I've been spoiled by the huge convenience of the DSLR. There are no pixel-peeping issues here. The greater efficiency (convenience) factor of the digital camera is so great, it dwarfs all other considerations. I have dozens of packets of film still in the fridge but well past their use-by date, both MF and 35mm.

Having bought additional lenses in the meantime for the D60 and 20D, I now have a focal length range, in 35mm terms, of 16mm to 900mm (using a 1.4x converter) with just 3 lenses.

All that remains is for Canon to produce an upgrade to the 20D which matches or exceeds the performance of the D2X, has autofocus capability at f8 and costs significantly less than the D2X.

I'm with you Canon! You can do it ! The money's in the bank waiting  :D .

There is where it falls down a bit; in practice the lens interchangeability is not so good, in large part due to the dominance of zoom lenses, whose preferred focal length ranges tend to be rather format specific.

The great majority of lenses being bought and used with DSLRs now are either unusable with 35mm format (Nikon DX, Canon EF-S, Olympus 4/3, Pentax DA, Minolta DT, Sigma DC, etc.), or are zoom lenses of focal length ranges that are inconvenient and unpopular with 35mm format (like 50-200 f/4-5.6: not many people use cheap, slow, 200mm zooms with 35mm format DSLRs do they?)

It works a bit better for the small elite who go the other way: those who primarily use high end 35mm format DSLR bodies and lenses can use all those lenses when occasionally slumming it with a smaller format, augmented by a few "D" lenses. Even then, lenses like 24-70 or 28-70 give a somewhat unpopular FOV range when cropped (would you buy a 40-110 lens for 35mm format?)

The makers of several different SLR formats (like Pentax, Mamiya, Fuji and Bronica) never did a lot in the way of cross-format lens compatability. This is probably a sign that there are performance virtues to using a lens designed for the format in use, rather than one for a format more than twice as large.

BJL,
I was always interested in that idea. It's just that I've been unduly influenced by knowledgeable people telling me that the 1Ds had already reached the resolution limits of 35mm format lenses. When the 1Ds Mkll came out, there was great skepticism that those smaller pixels would serve much purpose.

We now find that a smaller format camera with a 1.5 crop factor and a pixel density equivalent to 27mp on a 35mm format sensor (the D2X) delivers better image quality than the 1Ds and almost matches the resolution of the much more expensive 1Ds Mkll.

Which is more likely; that Canon will eventually produce an upgrade to the 20D that matches the performance of the D2X but at a lower price, or that Canon will eventually produce a much cheaper version the the 1Ds Mkll?

As Ray said, the comparison seems fair, in the sense that those "equivalent apertures" gather light from the subject at the same total rate, and so can deliver the same amount of light to each pixel (if pixel counts are equal), and so potentially the same "signal" at each pixel. (Eqivalent DOF and diffraction effects too, but I should pass on that one!)

The mathematics: Intensity of illumination per unit area is measured by aperture ratio, so total rate of illumination of the whole sensor is measured by sensor area divided by the square of the aperture ratio.


If noise levels per pixel were similar, you might be fairly close to image quality parity in many respects (though probably not dynamic range).

In practice a few things are likely to complicate the comparison. For examples of one going in each direction,
1) far larger sensors with larger pixels are likely to have an advantage in light detection efficiency, due to more precise operation of the larger microlenses
2) smaller pixels will produce less dark current noise, some sources of which follow a "per unit area" empirical pattern.

Ray, I will not repeat my calculations unless there is demand, but I am fairly sure of the following [and optimistic but less sure of the guesses in brackets.]

a) once controllable noise sources ("total dark noise") are reduced enough and photon shot noise is the limit, there is no advantage to image merging; the S/N ratio at any given pixel is determined simply by the number of photons used to make that pixel, due to that square root law.
[Dark noise levels seem to be approaching this point, for photographic purposes; maybe within one stop or so?]

dynamic range is indeed a clear current advantage to larger photosites and sensors; DR expansion strategies like frame blending will potentially neutralize that advantage, but no more.
[My guess is that in-camera and even in-sensor methods will eventually take care of DR limits, without need for multiple exposures and stationary subjects.]

c) since DOF and diffraction limitation for the same FOV are equal for the same aperture diameter (f-stop proportional to focal length), the two likely limits to small formats and photosites are that (1) photosites have to be bigger than the wavelength of light, and (2) lens abberations probably set a lower limit on aperture ratio, more or less independent of format, if one seeks images that are "sharp and contrasty from corner to corner". With current DSLR formats, limit (1) only comes in at extremely high pixel counts, and at extremely larger apertures due to diffraction limitation, so lens abberations seem likely to be the main practical limit in the long run.

[My current guess is that about f/2 might be the limit, and maybe not even that low; if so formats much smaller than the current smallest DSLR formats will always be distinctly hampered. Lower f-stops work with some 35mm lenses, but with extremely shallow DOF that probably hides sharpness limitations towards the edges of the frame. My optimism about f/2 in a small enough format comes from the apparently good corner to corner, wide open performance of the Olympus 4/3 format 50/2 and 150/2 lenses, including MTF 50% and better at 60lp/mm. But these are both "narrow FOV lenses", 24º and 8º respectively; edge and corner performance on normal to wide lenses is a tougher design challenge.]


Good hints as to the lens design limits of smaller formats might keep coming from Olympus in particular, as they are working wth the smallest SLR format, and are the only company designing new lenses reaching f/2 for any of the new DSLR formats, and the main one designing new primes for these formats. (To be fair, the new Nikon 200/2 might count as a digital, DX format oriented design, despite also working with 35mm format.) Another coming indication of the current state of the art for low f-stops in smaller formats might be the wide open performance of the forthcoming Olympus constant f/2 zooms.

My fault. Rereading your earlier post I see you've got it all pretty much covered.

What's not clear is just what range of charges could such a small photosite, not much bigger than the wavelength of red light, hold?

Could in-camera blending of multiple exposures really neutralise the DR advantage of the larger format, ie., the signal-to-noise advantage of the larger pixel?

Currently, small format digicams have an obvious advantage of allowing the use of  faster shutter speeds for same FOV and same DoF shots. If I try to use the same f stop (say f2) with a larger format camera, I get extremely shallow DoF, which may be the opposite of what's required.

But isn't this advantage of the smaller format really illusory? I can trade off the superior S/N of those larger pixels by bumping up the ISO till I get the same shutter speed.

Example: Comparing a camera the size of the FZ20 with the 350D that Bobtrips referred to earlier; if we have a situation where the FZ20 will use 1/30th at f2.8 at ISO 100, then for the same FoV and equivalent DoF at the same ISO setting, we'd be using about 1/2 sec exposure at f10.36. But we've got the option of using ISO 1600 with the 350D which would bring us a back to a shutter speed of 1/30th.

Now, without getting into arguments about which image would be superior (which will depend on a range of other noise reduction technologies that may have or may not have  been implemented in a particular camera), I think it would be fair to say in principle that the speed advantage of the smaller format has already been neutralised and is therefore an illusion.

If we take these trade-offs to the nth degree and begin implementing in-camera blending of multiple frames, we arrive at a point where the speed advantage of the smaller format is no longer illusory. It becomes a real disadvantage.

For example: Starting with an exposure in accordance with the sunny 16 rule, a contrasty outdoor scene will require 1/100th sec at ISO 100 and f16, or 1/400th at f8 (I've found this to be an excellent approximation).

If we consider the imaginary camera I've designed with a diffraction limited F1/5.4mm lens with equiv DoF to a 35mm FF 43mm lens at f8, the exposure required at F1 for that same contrasty scene would be 1/25,600 of a sec. And that just gets us the highlights.

If we take a series of shots, say 8 separated by 1 stop intervals (not by any means an excessive quantity considering what people are already doing in PS CS2's HDR), we arrive at a total exposure time of 1/100th sec. And that's not counting any delay between one shot and the next.

At the end of the day, the photon shot noise seems to be the insurmountable barrier as well as diffraction.

I find that difficult to believe BJL. You seem have every angle of this comparison between small and large format covered in terms of mathematical relationships and trade-offs almost  :) .



Not quite. As I've understood it, this advantage is completely offset by the increasingly larger role of photonic shot noise as the sensor gets smaller.



Now I know that you know there are huge economic factors which have had a major influence on this downward shift in format size in the digital era. The general public doesn't need or want digital backs that cost as much as a luxury car in order to produce 30x40" prints as sharp as drum-scanned 4x5 film. Even when it was quite clear that 35mm film could never compete quality-wise with MF film, the action still remained around the development of ever more sophisticated 35mm cameras.

I'm simply trying to find a real advantage to the smaller format other than weight and price. Perhaps this is because I don't use my Sony DCS T1 much.



I might have missed that particular thread, but thanks for mentioning it again. It makes perfect sense the way you've phrased it but leaves one wondering about the happy coincidence that such a simple rule should apply specifically to the 35mm format.

In any case, that's another possible advantage of the smaller format that lingered in my mind and has now been dashed  :) .