I had a canon rebel xt with 18-55mm "kit" lens for a few months and it just got stolen. i was happy with the body but need advice on a new lens.

in shopping for a new one i examined the images i shot already and found that they were not stiching together well (i use canon's stitch software). the corners were not matching up. in reading online reviews of that lens I learned that the corners of that lens distort more than the middle of the frame. i suspect that is why they are not stitching well.

my conclusion is that this lens is useless for my main project: stitched panoramas printed fairly large.

my question: what lens should i buy?

i loved the size and weight of the 18-55mm. it was wide enough for me although more zoom would be nice. i did notice the cheap build quality but image quality is more important.

my research so far is pointing me to:
canon 17-40mm f4 (this seems to get great reviews. expensive for me but might be my best option)
canon 20mm f2.8 (this fixed lens does not get the best reviews. if i got this one i'd need a second lens anyway so i wouldn't be saving much money buying a fixed lens)

i was using a powershot g2 for years. it's lens was (equivalent to) 35mm at it's widest. it worked ok but i want a little wider.

know of any non-canon lenses i should look at? $700 is the absolute max price.


if you are curious, see my panoramas here:
http://helloari.com/gallery/panorama/


thanks!
-/Å\-

You might want to try ptlens to correct your images before stitching.

As an all-around lens, I love my 17-40 f4L. I haven't yet tried it on panos, however.
As DarkPenguin suggests, it is pretty easy to correct distortion in software, so I'd look into ptlens or imagealign pro (which I use and find very easy). I use my Canon 17-40 on a 10D.

-Eric

helloari the simplest way to deal with your panorama alignment issue is to create image stitches from the use of more 'normal' focal lengths (around 28 OR 35mm lens setting on your Rebel XT's lens - I'm NOT refering to full frame equivalents).

This way when you over lap the images by 1/3 OR 1/2 a frame, there isn't as much angular difference between foreground elements when they're present on both the left and right of frame.

It also sounds to me like you're also missing the LCD image alignment function for panoramas that's present on many Canon digicams? Steady as she goes...

The simplest stiching comes from normal/longer lenses (35mm to 85mm - in full frame terms), but conversely the longer the lens the more time consuming it is to capture the greater number of frames in the field. It's a compromise.

As DarkPenguin pointed out you could correct your wide angle lens images with PT lens before stiching. PT Lens is a free Photoshop plug-in from: http://www.epaperpress.com/ptlens/index.html

You don't need to buy a better, faster OR wider lens for stitching panoramas (but you do need to buy a lens!). In fact wider lenses make it harder to stitch, but go ahead knock yourself out if you feel the need to buy a better/higher priced optic.

Das Bosun

I'd try one other software (free) - before spending any money - Microsoft Acrylic I have the August version, but it does a pretty good job of stitching and it might save you a couple of bucks. It will accept 16bit images, but seems to spit out an 8 bit pano...

Not hard, but its use isn't intuitive

File, New Vector Layer, OK
File, Insert Images (select the files you want) OK
Image, Stitch Selected Images - choose Common Vantage Point and Horizontal Cylinder - let it crunch
Object, Image, Export as Image File

at least, that's how it works in my version...

You're rotating about the nodal point (aka entrance pupil)? If not and there's close foreground, most programs will have some difficulty in dealing with the parallax.

As Das suggests, I'd be very surprised if it was the lens...

In truth, it depends on the program you are using to stitch the images together... If you are using something like PTAssembler, PTGui, or any other PanoTools front end GUI, you do not want to correct your images before stitching as you are essentially deforming your images twice. If you just stitch your images, your only have to deform your images once (less image degradation).

Some of the simpler Stitching programs though aren't able to handle lens distortion very well, in which case, you might be better off "correcting" your starting images. However, these same programs are also generally very limited (can't morph the image, stitch pictures with different dimensions, etc.), have difficulty dealing with multirow panos, and can't output multiple layer files (very useful for hiding seams, ghosting, parallex problems, etc), so, if you are serious about shooting panoramics, you might as well bite the bullet, spend $40 (or so) and invest the time (2-3 hours to become moderately proficient; if you just use the auto features, and there are minimal problems with your panorama (minimal parallax, etc.) you'll likely get an almost perfect stitch in under a half an hour) in learning how to use one of the PanoTools front end GUIs.

As for a good lens, I think a great lens for stitching (even on reduced frame DSLRs) is the 50mm f1.8. I have also made good multirow panos with the 17-55 mm lens that came with Digital Rebel...

JMB

To summarize, there are 2 possible causes for your problems:

1. The distorsion of the lens,

2. The fact that you are not rotating around the entrance pupil of your lens (beware, that point depends on the focal lenght used on the zoom lens).

For issue1, Another expensive, but high quality, option is to correct the distorsions of your lens with DxO Optics, and then use the pano software afterwards.

Most, if not all, pano software can only correct for simple barrel/percution distorsion but DxO is able to correct automatically for the actual field deformation that occurs with lenses.

I have been using it together with Stitcher 5.03 for very fast and remarkable results.

I'll try comparing Stitcher with PTgui one of these days though.

Regards,
Bernard

thanks for all the great advice. i have only done quick stitches with canons photostitch so far. i have done many panoramas so it's high time i made the effort to learn some more sophisticated software.

i dont want to use "normal" lenses because i like having a wider view. it makes sense to have a better quality lens that is not only sharper but shows less vigneting in addition to a "smoother" distortion that i mention above.

any other suggestions for mac panorama software are welcome. i only output flat stitched images so i dont need qtvr options. i dont think i would do multi row stitches but maybe i should try it out.

yes, i generally hand hold these which causes some headaches in fixing seams but also can lead to some welcome surprises and unique subtle distortions.

Won't a simple ultra-wide lens be good enough?

If I had an EF-S capable body I'd surely buy the 10-22 USM. As I don't (1D), I consider buying it anyway and modify it to EF.

Moderate barrel or pincushion distortion is not an issue for the better stitching tools, like PTAssembler or PTStitcher, because they are capable of correcting such distortions as they do the stitch. Less capable tools like Canon's program don't have that capability and are much less usable as a result. All you should be concerned with is getting a decent quality lens that gives sufficient vertical angular coverage when the camera is oriented portrait-style. An ultra-wide like the 10-22 is unnecessary unless you intend to make 360° spherical panos. For most landscapes, a 17-40 or 24-70 is more than wide enough even on a 1.6x body. On a full-frame body, a 70-200 is often an appropriate choice.

Remember, when shooting stitched panos you're getting your vertical angular coverage from the long dimension of the sensor, not the short, so you can use a lens 1.5x longer than you would if you had the camera horizontal and were capturing the image in a single frame. Your horizontal angle of coverage is limited only by the number of overlapped frames you shoot.