08-10-2010, 02:34 PM
[quote name='wim' timestamp='1281447464' post='1633']
Keyword here is slightly, I think, and that is what I meant. When you get to this class of lenses, the end results are in the rendering and PP, not in the quality the lens delivers. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />[/quote]
Yep. Still, I have some hope the AF-S will be better. Not much, though. In fact, I usually tend to be rather pessimistic ... but prepared for the best <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='B)' />
[quote name='wim' timestamp='1281447464' post='1633']
I don't think so, because focus shift is relative, and at larger distances (let's say > 2 m) focus shift disappears. At least, that is my experience with lenses that display focus shift (Sigma 50 F/1.4, 50L, 85L II <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />). IOW, not because it disappears with DoF (that too at smaller apertures), but because it literally disappears slowly with distance, to disappear completely from a certain distance onwards.[/quote]
I see some potential for additional review work here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='' /> Seriously though: from my experience the focus shift remains visible in normal working distances with these lenses. At least with the Sigma ...
[quote name='wim' timestamp='1281447464' post='1633']
Interesting. Not completely APO then <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='' />. Also interesting that the focus shift doesn't get less with distance. Quite a different experience from the one I had so far.[/quote]
Nope, only focus miscalibration. The lens was simply backfocusing, and that becomes more obvious with larger subject distance.
I haven't tested for focus shift, yet, but you're right about not being an APO lens ... at least not in the sense we usually look at it (truely apochromatic). It shows a considerable amount of LoCAs.
[quote name='wim' timestamp='1281447464' post='1633']
Well, it is as it is I guess. It is the official term for longitudinal CAs.
[/quote]
Well, I was just wondering, because I couldn't find really useful information.
However, to get to the point that's probably more important (people mixing up lateral CAs and LoCAs): maybe we should add some links to a lens test FAQ or place some short explanations within the reviews.
-- Markus
Keyword here is slightly, I think, and that is what I meant. When you get to this class of lenses, the end results are in the rendering and PP, not in the quality the lens delivers. <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />[/quote]Yep. Still, I have some hope the AF-S will be better. Not much, though. In fact, I usually tend to be rather pessimistic ... but prepared for the best <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='B)' />
[quote name='wim' timestamp='1281447464' post='1633']
I don't think so, because focus shift is relative, and at larger distances (let's say > 2 m) focus shift disappears. At least, that is my experience with lenses that display focus shift (Sigma 50 F/1.4, 50L, 85L II <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/biggrin.gif' class='bbc_emoticon' alt='
' />). IOW, not because it disappears with DoF (that too at smaller apertures), but because it literally disappears slowly with distance, to disappear completely from a certain distance onwards.[/quote]I see some potential for additional review work here <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/wink.gif' class='bbc_emoticon' alt='
' /> Seriously though: from my experience the focus shift remains visible in normal working distances with these lenses. At least with the Sigma ...[quote name='wim' timestamp='1281447464' post='1633']
Interesting. Not completely APO then <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/smile.gif' class='bbc_emoticon' alt='
' />. Also interesting that the focus shift doesn't get less with distance. Quite a different experience from the one I had so far.[/quote]Nope, only focus miscalibration. The lens was simply backfocusing, and that becomes more obvious with larger subject distance.
I haven't tested for focus shift, yet, but you're right about not being an APO lens ... at least not in the sense we usually look at it (truely apochromatic). It shows a considerable amount of LoCAs.
[quote name='wim' timestamp='1281447464' post='1633']
Well, it is as it is I guess. It is the official term for longitudinal CAs.
[/quote]
Well, I was just wondering, because I couldn't find really useful information.
However, to get to the point that's probably more important (people mixing up lateral CAs and LoCAs): maybe we should add some links to a lens test FAQ or place some short explanations within the reviews.
-- Markus
Editor
opticallimits.com
opticallimits.com