07-05-2012, 11:42 PM
[quote name='Rainer' timestamp='1341426858' post='19318']
Well, if you've tried to focus with liveview and this does not
change your results, you can at least exclude the AF system.
The results are (in that case) as sharp as your sample of the
lens gets.
So, you might have expectations that cannot be matched
by an ultrawide lens, or you might have a bad sample. THat is
actually very hard to tell without a sample image.
From my personal experience, most ultrawides do not (never at
no setting) get that sharp as a good telelens gets ... even if testsites
see their MTF values around the same values. The best you can do
is use a tripod, stop down, use mirror lockup and a cable release.
Just my 2 cts ... Rainer
PS: First post ... welcome at PZ !
[/quote]
Ah, I appreciate your reply. I have one general question about it though...when you say it might be a bad sample, what exactly does that mean? How do I know? Does a bad sample mean it should be sent to Sigma? Is there a way to test it myself?
Thanks, this is a great forum!
Well, if you've tried to focus with liveview and this does not
change your results, you can at least exclude the AF system.
The results are (in that case) as sharp as your sample of the
lens gets.
So, you might have expectations that cannot be matched
by an ultrawide lens, or you might have a bad sample. THat is
actually very hard to tell without a sample image.
From my personal experience, most ultrawides do not (never at
no setting) get that sharp as a good telelens gets ... even if testsites
see their MTF values around the same values. The best you can do
is use a tripod, stop down, use mirror lockup and a cable release.
Just my 2 cts ... Rainer
PS: First post ... welcome at PZ !
[/quote]
Ah, I appreciate your reply. I have one general question about it though...when you say it might be a bad sample, what exactly does that mean? How do I know? Does a bad sample mean it should be sent to Sigma? Is there a way to test it myself?
Thanks, this is a great forum!