Hello - I'm new to photozone, bu was really impressed by the in-depth reviews. I have just received a brand new Canon EOS 7D and EF-S 17-55mm IS USM. I am generally delighted with the 7D and the 17-55, but have found some significant vignetting at wide aperture and shorter zoom. All four corners of images fall off gradually, and significantly. I realize some vignetting is to be expected under these conditions, but wonder if what I am experiencing is beyond expectations (i.e. did I get a lemon, either in the camera body or lens)? I've included a sample image below:
[url="http://www.flickr.com/photos/54159846@N08/5005674256/"]Sample photo[/url]
The photo was shot at 17mm, f/6.3. Additionally I have a UV filter and a polarizer attached (both from Crystal Optics).
Any comments would be greatly appreciated!
"Additionally I have a UV filter and a polarizer attached"
There is your problem! At 17mm using a single filter will be ok but doubling them up will cause heavy vignetting. Why do you have 2 filters on? Is it because you have the UV permanently bolted on through fear of dust on the 17-55? If not, then I cant imagine why one would ever mount a UV filter on a DSLR. (My guess is that this vignetting would probably disappear by about 25-30mm if you did have 2 filter on...)
Allan
[quote name='Birefringent' timestamp='1284926278' post='2933']
Additionally I have a UV filter and a polarizer attached
[/quote]
This is the reason for your problem. You should not mount more than one filter at a time.
-- Markus
That's actually mechanical vignetting from the filters.
First of all, you should always only mount 1 screw-in filter only, as more than one is a guarantee to get mechanical vignetting. In short, always only one of these filters at a time, never both of them simultaneously.
Furthermore, depending on the thickness of the polarizing filter, which normally is a few millimetres thicker than a normal filter, you may still get mechanical vignetting with some, and none with others. This is something you may have to determine empirically.
Kind regards, Wim
Thanks very much for the comments. Clearly stacking the filters is a bad idea. The impulse is indeed to protect the expensive lens, but at the cost of reducing it's quality? Will unstack and give it another go.
All the best.
[quote name='Birefringent' timestamp='1284944850' post='2941']
Thanks very much for the comments. Clearly stacking the filters is a bad idea. The impulse is indeed to protect the expensive lens, but at the cost of reducing it's quality? Will unstack and give it another go.
All the best.
[/quote]
It's fine to protect your costly lens. However, 1 filter is good enough for protection. Two is overkill, and will give effects as you already noticed.
The only time when you use more filters is with a creative filter system, like Lee, Hitech, Cokin. However, if you get the correct filter system for your lenses, stacking filters does not introduce vignetting up to 3 or 4 filters, because the filter holder and filters are wide enough to prevent vignetting.
Kind regards, Wim
Thanks much for the tip. Just to follow up: I've now had a chance to removed the filters and take a few shots. Without filters, no vignetting. With one filter (either one), little or none. This is really a great system and I am very happy this is resolved. Thanks again for the patient advice.
All the best.
[quote name='wim' timestamp='1284966668' post='2947']
It's fine to protect your costly lens. However, 1 filter is good enough for protection. Two is overkill, and will give effects as you already noticed.
The only time when you use more filters is with a creative filter system, like Lee, Hitech, Cokin. However, if you get the correct filter system for your lenses, stacking filters does not introduce vignetting up to 3 or 4 filters, because the filter holder and filters are wide enough to prevent vignetting.
Kind regards, Wim
[/quote]
[quote name='Birefringent' timestamp='1284985795' post='2976']
Thanks much for the tip. Just to follow up: I've now had a chance to removed the filters and take a few shots. Without filters, no vignetting. With one filter (either one), little or none. This is really a great system and I am very happy this is resolved. Thanks again for the patient advice.
All the best.
[/quote]
Another question if you don't mind:
What do you mean with little or none with either one <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />? Is it the same fairly sharply delimited mechanical vignetting or just a slight, gradual darkening of the corners, i.e., optical vignetting (which will be worse close to infinity than close to MFD, where it likely will be invisible)?
If it is the latter, you can switch on ALO (Auto Lighting Optimizer; Custom Functions) which will get rid of vignetting in your jpegs if you shoot those or process your images in DPP.
BTW, I did test one or two 17-55s a couple of years ago, and I found it had some vignetting at 17 mm mostly, which disappeared relatively quickly for the largest part when zooming in, or when stopping down a bit.
Kind regards, Wim
[quote name='wim' timestamp='1284987277' post='2977']
Another question if you don't mind:
What do you mean with little or none with either one <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />? Is it the same fairly sharply delimited mechanical vignetting or just a slight, gradual darkening of the corners, i.e., optical vignetting (which will be worse close to infinity than close to MFD, where it likely will be invisible)?
If it is the latter, you can switch on ALO (Auto Lighting Optimizer; Custom Functions) which will get rid of vignetting in your jpegs if you shoot those or process your images in DPP.
BTW, I did test one or two 17-55s a couple of years ago, and I found it had some vignetting at 17 mm mostly, which disappeared relatively quickly for the largest part when zooming in, or when stopping down a bit.
Kind regards, Wim
[/quote]
I mean that there is still some gradual fall of in image intensity at the corners when the lens is at 17mm and the aperture is wide open. Perhaps this should not be called vignetting, but rather spherical aberation due to using a larger extent of the lens. As you suggest, the effect is minimized as I zoom in a bit or if the aperture is stopped down a bit. I am not 100% convinced that one filter and no filter are any different. Probably the best way to determine that would be to shoot a wall of uniform color and illumination with and without a filter. At any rate, the sharp mechanical vignetting is no longer present, and I am very glad for that!
All the best.
[quote name='Birefringent' timestamp='1285020769' post='3015']
I mean that there is still some gradual fall of in image intensity at the corners when the lens is at 17mm and the aperture is wide open. Perhaps this should not be called vignetting, but rather spherical aberation due to using a larger extent of the lens. As you suggest, the effect is minimized as I zoom in a bit or if the aperture is stopped down a bit. I am not 100% convinced that one filter and no filter are any different. Probably the best way to determine that would be to shoot a wall of uniform color and illumination with and without a filter. At any rate, the sharp mechanical vignetting is no longer present, and I am very glad for that!
All the best.
[/quote]
Actually, what you describe is the optical vignetting I was referring to, and I do expect a single filter or the absence of a filter not to have any effect on this either, as a lens normally is designed to take at least 1 filter of a standard size and thickness, without causing mechanical vignetting. You can read a little on optical vignetting here:
[url="http://www.opticallimits.com/lens-terminology"]http://www.photozone...ens-terminology[/url]
Spherical aberration is something completely different; you can read more about it here:
[url="http://toothwalker.org/optics/spherical.html"]http://toothwalker.o.../spherical.html[/url]
Kind regards, Wim