Strange dark corners

[weazle1098]

I noticed today that in photos that I take with my Canon Rebel XTi, where there is a single background color, the corners seem to be darker than the rest. I figure its probably lens, its a Sigma 18-200mm, but I was wondering if there was any way to counter this. Any way i posted a bad shot but it suits the purpose of this…

 

[dllavaneras]

Check the EXIF data, the dark corners (vignetting) are probably caused by using a large aperture (f2.8 or the largest your lens has). Stopping down the lens a stop or two should do the trick.

 

[Grimace]

we call that vignetting. It's a common problem - especially when a lens is at its widest. Top glass won't have this problem as much, but it does affect us all at some point...

 

[dllavaneras]

Yes, but a 18-200 zoom has to have some compromises I've heard great things about that lens when it's stopped down, so try reducing the aperture a bit. Hope this helps!

 

[Abstract]

With any zoom that goes to focal lengths 18 and below, you're bound to get some vignetting from a zoom. In fact, you're going to get weird distortions and stuff at the extremes of any zoom, and the larger the range, the more of these distortions and "bad things" you'll see, which is why not every person rushes out to buy a single 18-200 mm lens that can do it all. If it was the fracking holy grail of lenses, and suffered no distortion at all, and was a fairly fast lens, it would be on everyone's list of lenses to get.

The only zoom lens with a large range I can think of that shows very few flaws is the one that comes with the Sony DSC-R1 (can shoot 14.3 - 71.5 mm), and that camera isn't a DSLR, which means it's attached to the camera, so you'd have to buy the entire camera to get that lens. Nice camera, good photo quality, but more expensive than my DSLR. Fantastic lens, though.

If you shoot at f/5.6 or f/8, watch the photo get more "even".

 

[eXan]

I noticed today that in photos that I take with my Canon Rebel XTi, where there is a single background color, the corners seem to be darker than the rest. I figure its probably lens, its a Sigma 18-200mm, but I was wondering if there was any way to counter this. Any way i posted a bad shot but it suits the purpose of this…

This can be currected in Photoshop's "Lens Correction" filter.

 

[EstorilM]

we call that vignetting. It's a common problem - especially when a lens is at its widest. Top glass won't have this problem as much, but it does affect us all at some point...

Yeah, edge fall-off is common in non-pro lenses, and VERY high ratio zooms such as the 18-200. I think the newer ones (Nikkor 18-200 VR) did a little better in this test. That's pretty extreme to be honest with you, the exposure might be a little off as well.

 

[weazle1098]

Thanks a bunch

I thought that may have been it, but thanks a bunch gentlemen.

 

[Grimace]

I've seen this problem the most with Sigmas that have big ranges. I like Sigma (especially for 17-70mm range) but you'll find better results with Canons and Nikons that have large ranges. I know that doesn't help you now but it may help others who are doing post-holiday shopping!

 

[weazle1098]

Yeah, edge fall-off is common in non-pro lenses, and VERY high ratio zooms such as the 18-200. I think the newer ones (Nikkor 18-200 VR) did a little better in this test. That's pretty extreme to be honest with you, the exposure might be a little off as well.

Yeah, my dad bought me the camera and lens, so I can't complain, because I couldn't afford it at all, but I am saving up for an L grade lens, which one, I'm not quite sure yet, but as a college student I'm poor

 

[compuwar]

If it's at 18mm, you may want to see if theres an issue with a lens hood or filter ring, just in case.

 

[EstorilM]

Yeah, my dad bought me the camera and lens, so I can't complain, because I couldn't afford it at all, but I am saving up for an L grade lens, which one, I'm not quite sure yet, but as a college student I'm poor

Yeah I understand, I wouldn't complain either! I saved up for soo long to get this setup, it's a good feeling when you need to get a bigger camera bag.

It'll be tough to find any L lens with that kind of width though, I know with Nikon I'm looking at the 12-24 f/4 and that's gonna run me ~$900, but the thought of having that focal length range for landscapes and stuff is sooooo tempting. Right now my widest is 24.

 

[coldrain]

Yeah I understand, I wouldn't complain either! I saved up for soo long to get this setup, it's a good feeling when you need to get a bigger camera bag.

It'll be tough to find any L lens with that kind of width though, I know with Nikon I'm looking at the 12-24 f/4 and that's gonna run me ~$900, but the thought of having that focal length range for landscapes and stuff is sooooo tempting. Right now my widest is 24.

Canon does not make EF-S "L" lenses (EF-S is what DX is for Nikon). But that does not mean that Canon does not make L quality optics in EF-S form factor, they do. The EF-S 10-22 f3.5-4.5 USM has the exact same configuration in UD elements as the 17-40 F4 L USM for instance, and is for APS-C what the 17-40 is for full frame. Also the 17-55 f2.8 IS USM has "L" glass inside.

 

[compuwar]

I know with Nikon I'm looking at the 12-24 f/4 and that's gonna run me ~$900, but the thought of having that focal length range for landscapes and stuff is sooooo tempting. Right now my widest is 24.

If your primary use is landscapes, a pano head is likely to be a better option.
If you're looking at moving subjects like street scenes, you might find the following comparison interesting (note the site does have a bias for Nikkor glass.)

http://www.nikonians.org/html/resources/nikon_articles/nikkor/af/wide_angles_shootout/index.html

 

[EstorilM]

If your primary use is landscapes, a pano head is likely to be a better option.
If you're looking at moving subjects like street scenes, you might find the following comparison interesting (note the site does have a bias for Nikkor glass.)

http://www.nikonians.org/html/resources/nikon_articles/nikkor/af/wide_angles_shootout/index.html

Yeah I've read that a few times, however I've also used a number of 3rd party optics in the past and - regardless of what the reviews say, I'm always disappointed. I've never had the same confidence level with my sigma lenses as I get when I pick up the Nikkor lenses. I never really stop being impressed with the images coming from their lenses, on the other hand, it's really easy to find performance holes in the sigmas.

It sounds stupid, but all things being equal, I'd rather have the nikkor in my bag. The 5 year warranty is also nice.

edit: Most of the stuff I do is sports, but it would be nice to catch the "big picture" every now and then, in the summer I find myself doing a lot of storm photography and wildlife scenery. I think the 12-24 is the focal length I really need - I've also played around with the 17-35 2.8 which was pretty incredible, but it's almost as much as my 70-200VR which is really too much for me to spend on exotic focal lengths.

 

[compuwar]

Yeah I've read that a few times, however I've also used a number of 3rd party optics in the past and - regardless of what the reviews say, I'm always disappointed. I've never had the same confidence level with my sigma lenses as I get when I pick up the Nikkor lenses.

I found my sample of the Sigma 50-500 to give better images than my sample of the Nikkor 80-400VR, though I liked the contrasty look from the Nikkor. It's all about results to me.

While I prefer Nikkors in general, the 12-24mm falls a little short IMO.

I think the 12-24 is the focal length I really need - I've also played around with the 17-35 2.8 which was pretty incredible, but it's almost as much as my 70-200VR which is really too much for me to spend on exotic focal lengths.

I've got a 20-35mm AFD lens that I like a lot for landscapes, though I did see some CA shooting directly into the sun this weekend. The small printer I use for proofs really doesn't have the DR to tell how bad it'll be printed well though. I've been pondering getting the Sigma 10-20 though, might be an interesting lens.