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+--- Thread: Pentax 31mm unsharp at 1.8 (/showthread.php?tid=3063)
Pentax 31mm unsharp at 1.8 - chals - 07-24-2011
I bought the Pentax 31mm f1.8 because I wanted a sharp lens with good bokeh to go with my Pentax K5.
Based on the review (and pictures) here and other places, i expected better results at 1.8 than the picture at this link: http://chals.zenfolio.com/p296791352/h133dcd4?#h133dcd4
The result are always like this, far away or close.
Can someone here who know the lens tell me if there is something wrong with my copy.
Pentax 31mm unsharp at 1.8 - Rainer - 07-24-2011
What are you showing us in the linked image?
The image does not contain exif-data or description, it is by far to small
to say much about it, you don't tell about the circumstances under which
you took those images ... this seems to a clear case for my cristal ball ...
but is that the type of answer you are looking for?
Pentax 31mm unsharp at 1.8 - chals - 07-24-2011
the picture is a dump from LR at 200% . Aperture is 1.8 and 2.8 shutterspeed is 1/2000 for the 1,8 shot. i think it is possible to judge the pictures, espesially if you have seen a sharp/unsharp 31mm ltd before
Pentax 31mm unsharp at 1.8 - Rainer - 07-24-2011
Well, the obvious first:
The f-2.8-image is better than the f-1.8-image ... this is something very common ...
use a lens wide open, and use it stopped down a bit, and image quality increase.
What I don't like, is (besides reduced contrast which would be ok) the way it behaves
on the contrasty white edge ... this seems to me as if a cheap UV filter has been on the
lens when taking this image. I mean ... it is clear that this shot is for test purposes ... since
there is nothing in this image requiring f/1.8 ... nevertheless, one wouldn't expect this in the
image center.
Pentax 31mm unsharp at 1.8 - Klaus - 07-24-2011
[quote name='chals' timestamp='1311537795' post='10218']
the picture is a dump from LR at 200% . Aperture is 1.8 and 2.8 shutterspeed is 1/2000 for the 1,8 shot. i think it is possible to judge the pictures, espesially if you have seen a sharp/unsharp 31mm ltd before
[/quote]
Looking at this odd halo effect I suspect a centering issue.
Please check ...
http://forum.photozone.de/index.php?/topic/830-do-it-yourself-centering-sanity-check/page__p__7409__hl__decentered__fromsearch__1#entry7409
Pentax 31mm unsharp at 1.8 - chals - 07-25-2011
thank you very much for the tip, I will perform this test as soon as I get back from holiday. When using a Pentax K5 with tripod and AF focusing; the result will be unsymetrical and somewaht blurres images on edges(not the eges of the frame) of the target object. Probably a good idea to test the 18-135 zoom at 31mm focal length too?
Pentax 31mm unsharp at 1.8 - Klaus - 07-25-2011
[quote name='chals' timestamp='1311582322' post='10223']
thank you very much for the tip, I will perform this test as soon as I get back from holiday. When using a Pentax K5 with tripod and AF focusing; the result will be unsymetrical and somewaht blurres images on edges(not the eges of the frame) of the target object. Probably a good idea to test the 18-135 zoom at 31mm focal length too?
[/quote]
In the dead center the edges should be perfectly symmetrical regardless of the lens.
You can, of course, check the 18-135 but this is independent from the 31 in any case (unless we are talking about a camera defect).
Remember to switch off SR for the procedure.