Hi All. I've been looking at a Cambo WDS system as a possible additional platform for my P45. It has lens panels ranging from 24mm thru 90mm. If I've done my math correctly, that translates into roughly 6.6mm thru 25mm in 35mm terms. Which seems like an absurd range, so I suspect I HAVEN'T done my math correctly.

So, for a Cambo system (or Alpa, or any other equivalent technical system), what is the focal length mulitplier for converting to 35mm equivalent focal lengths when using the P45 (or similar sized) back?

To get the numbers I came up with, I divided the 35mm diagonal by the 4" x 5" diagonal, and multiplied the resulting number by the Cambo (actually Schneider and Rodenstock) focal lengths. But as I said, I came up with seemingly absurd results.

Regards,
Mort.

I think your error was using 4x5 specs...Do the same math using 6x9 cm specs..that's what the Wide DS and associated lenses are designed to cover.

You're right, I did use the 4"x5" diagonal, which is what Schneider's literature used when they did their focal length mulitiplier calculations for the lenses used on the Cambos. But lets assume it's 6cmx9cm. That translates to 10mm thru 39mm in 35mm terms, which still seems like a very limited range to me. For landscape work, I'd like to be able to go up to at least 85mm in 35mm terms.

A 90mm lens on a P45 is a little longer than "normal" maybe by 10%-15%

I tend to relate to medium format numbers only so I won't comment on 35mm.

Think of the lenses as though they were on your medium format camera with your P45 on it.

As a wide angle solution the Cambo Wide DS is wonderful, as a longer lens solution, not so much. Also, remember that when using longer lenses you'll probably not want to do shifts and rises, so your regular medium format camera will do the job just fine (not taking into account any lens quality differences, I'm not going there)

Yes, but that's a 645-format 90mm. A 4"x5" 90mm is a wide angle on a 645 system. I use both 35mm and 645 systems, so I understand the differences there. A 90mm Cambo WDS lens is not the same focal length as a 90mm 645 system lens (or maybe I should just say that the field of view is totally different). At least that's what I think. I'm obviously missing something here. Cambo references a Schneider document on their lenses, and that document indicates you divide the Schneider focal lengths (for the Cambo system) by 3.6 to get to 35mm equivalents. But that yields results which just don't seem right to me. Which is why I'm asking my question. Hmmmmm.

Try this online calculator just put the mm L and W of the sensor in

http://www.imaginatorium.org/stuff/angle.htm

Huh???

You'll get exactly the same angle of view with any 90mm lens....period.

Thats not true at all. The angle of coverage has everything to do with lens design. Just take these examples from the old view camera days ...

A Schneider 90mm Angulon had a 100 degree Coverage.

The next generation Schneider 90mm Super Angulon had a 105 degree Coverage

And the last generation Scheider 90mm Super Angulon XL had a 110 degree coverage.

Exactly. And a 90mm lens for a 35mm camera has a field of view of roughly 27 degrees. A 90mm lens for a 645 body has something in-between. Very confusing.

If you want to campare focal length equivalents for the P45 versus 35mm (full frame) then compare the diagonals of the frames and use that ratio to compare focal lengths.

For example P45 is approximately 60mm diagonal, 35mm frame is approximately 43mm diagonal, therefore the ratio is approximately 1.4:1. So divide the lenses used with the P45 by 1.4 and you get their 35mm equivalent.

Schneider 24 XL Digitar on P45 = 17mm lens on 35mm
Rodenstock 28 HR Digital on P45 = 20mm lens on 35mm
Schneider 35 XL Digitar on P45 = 25mm lens on 35mm
Schneider 47 XL Digitar on P45 = 33mm lens on 35mm

etc up to

90 Digitar on P45 = 64mm lens on 35mm


Specific fields of view are affected by the individual lens designs but that gives you an idea of equivalents. Obviously these are just rough calculations as I was rounding to the mm but you get the idea. What camera they are used on is irrelevant to the calculations, Cambo, Alpa, Arca, Horseman etc, only the film/sensor/lens dimensions.

Hope that helps.

Matt

Mort,

Matt knows what he's talking about.

The Cambo WDS is a modular system that can be used for digital as well as film formats upto 4"x5". I use one with my Betterlight and film, sheet as well as rollfilm. It has a standard Graflok fitting, so you can use most rollfilm holders made for 4"x5" cameras. Lenses are available from 24mm to 150mm, both digital and film versions. Cambo will also mount some lenses as a special order. For digital use, you only have to change from the standard film back to a digital back. The digital lenses have smaller image circles and are optimized for the digital format - f8~f11.

Cheers,
Kumar

But the angulon just covered 4x5 the SA almost covered 5x7 and the SA XL covered 5x7. If you shoot a sheet of 5x7 film with a 90mm lens and them shoot the same scene with a 645 camera and cropped down the 5x7 image to match the 645 you'll see the exact same image characteristics.

Matts format conversion is pretty spot on though you have to take into account the format aspect ratios.

Also its my experience that if you get the wds with a 4x5 rotating back you wont get the 24mm lens to focus. I have the afd mount and like it alot but wish they would make a focus screen like they do for the HassyH1 mount. I'm seriously considering buying the H1 mount and ground glass just so I can focus and frame with out shooting test frames every setup. Also you can pretty easily shoot two frames and stitch them for wider views.

Alpa has a Comparable Focal Length Calculator on their web site.

http://www.alpa.ch/index.php?path=knowledgebase


Chris Lawery
Sales Manager
Capture Integration
www.captureintegration.com

see attached

I'm probably having a morning of being dense, but is this kind of hard to understand?

there doesnt seem to be a 50mm standard lens comparison in 35mm, for example...
48mm or 58mm but no 50mm.

and I note that Phase P25, P45, H25, etc are not highlighted green as "Main Alpa Formats" but Leaf backs all are.
hmmm.