08-16-2010, 03:56 PM
Hmm I'm still puzzled by how resolution can be affected by the angle of incidence without any added vignetting.
[quote name='wim' timestamp='1281541825' post='1678']
Regarding the size of the sensor, well that also has an effect. The larger the sensor, the wider the AoV will be for the same FL, and vignetting is directly, almost exponentially, related to AoV. That's the cosine rule I was referring to above. Whether a lens is designed for APS-C or for FF doesn't matter in this regard, the only dfiference will be the FL number on the lens for a similar AoV.
...
There are a few lenses that actually do better in this regard, the new TS-Es come to mind: they do better at least for the unshifted or untilted part of an image ... <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />. But then, they aren't very fast lenses either.
[/quote]
I'm not sure whether I agree with your first comment because as you said in the last part, a large image circle does help reduce the vignetting. Also there are many examples of the same focal length+max f-number combinations producing different levels of vignetting mainly because of design.
[quote name='wim' timestamp='1281541825' post='1678']
Well, the lack of distortion is IMO the only redeeming feature of that lens, for me anyway. I tested two for half a day, took the best one home, and was horrified by the vignetting in real life shots (at any aperture and FL), the CA, the behaviour with regard to flare and ghosting, and the blur or rather smearing towards the edges and in the corners. The only good part in the images was about a 1/3 crop, ok, maybe a 1/2 crop. And that was the better lens of the two. A third one I tried wasn't any better either.
[/quote]
Yes, it doesn't sound too different from what most people encounter with the 12-24, unfortunately. Not sure if you've seen the review below:
http://www.juzaphoto.com/eng/articles/si...review.htm
IMO, this is not the sharpest sample of the lens I've seen but it's still very good. There was another test from a lesser known guy somewhere on the net which was more of a chart test and the one he had was even more impressive.
GTW
[quote name='wim' timestamp='1281541825' post='1678']
Regarding the size of the sensor, well that also has an effect. The larger the sensor, the wider the AoV will be for the same FL, and vignetting is directly, almost exponentially, related to AoV. That's the cosine rule I was referring to above. Whether a lens is designed for APS-C or for FF doesn't matter in this regard, the only dfiference will be the FL number on the lens for a similar AoV.
...
There are a few lenses that actually do better in this regard, the new TS-Es come to mind: they do better at least for the unshifted or untilted part of an image ... <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />. But then, they aren't very fast lenses either.[/quote]
I'm not sure whether I agree with your first comment because as you said in the last part, a large image circle does help reduce the vignetting. Also there are many examples of the same focal length+max f-number combinations producing different levels of vignetting mainly because of design.
[quote name='wim' timestamp='1281541825' post='1678']
Well, the lack of distortion is IMO the only redeeming feature of that lens, for me anyway. I tested two for half a day, took the best one home, and was horrified by the vignetting in real life shots (at any aperture and FL), the CA, the behaviour with regard to flare and ghosting, and the blur or rather smearing towards the edges and in the corners. The only good part in the images was about a 1/3 crop, ok, maybe a 1/2 crop. And that was the better lens of the two. A third one I tried wasn't any better either.
[/quote]
Yes, it doesn't sound too different from what most people encounter with the 12-24, unfortunately. Not sure if you've seen the review below:
http://www.juzaphoto.com/eng/articles/si...review.htm
IMO, this is not the sharpest sample of the lens I've seen but it's still very good. There was another test from a lesser known guy somewhere on the net which was more of a chart test and the one he had was even more impressive.
GTW