Just a hunch, I don't have any hard knowledge on this....
I think one issue with wide-angles is that the all optical elements have to be properly centered. I know one German photo journal used to test this when doing MTF tests. Maybe a slight misalignment of an element could cause what you observe?
Jostein
----- Original Message ----- From: "Lasse Karlsson" <[EMAIL PROTECTED]>
To: <pentax-discuss@pdml.net>
Sent: Saturday, March 19, 2005 12:18 PM
Subject: Re: Could anybody explain this?
Hi Alan,
I can confirm that I make the same observations that you're reporting.
I have no explanation.
However, if someone had cut out the blurry part and asked me "what's up?" I would have said that from my experience it looks like blur from camera movement or shake.
This led me to ask myself, is it possible that (particularly) a wide angle lens, if being turned "around it's axis" in one direction during exposure, one utter side of the picture may get blurred in a similar way to your pictures, while the opposite side, for some physical/optical reason that I cannot explain, won't exhibit the same or equal (type of blur) blur?
I may be completely off here, I'm just theorizing from my initial observation of the blur (on which I may very well be mistaken on).
You know - I don't - the facts about the shooting, shutter speed and possible camera movement, which may completely eliminate.the grounds for my questions.
Just some food for thought.
Good luck, Lasse
From: "Alan Chan" <[EMAIL PROTECTED]> To: <pentax-discuss@pdml.net> Sent: Saturday, March 19, 2005 12:46 PM Subject: Could anybody explain this?
Guys I have discovered a weird problem which I cannot come up with any explanation
so I need some guidance. Some recent shots have revealed that about 1/5 on the
right-hand side of the picture is blurrier than on the left-hand side under normal
shooting condition (aperture f11 for all samples).
http://www3.telus.net/wlachan/cb.jpg (1.7MB)
To double check, 2 identical shots were done, 1 with the camera grip (blurry side)
pointing up (ru.jpg), and the other pointing down (rd.jpg). This test confirms the
previous finding. The bottom edge of rd.jpg is blurrier than the bottom edge of
ru.jpg.
http://www3.telus.net/wlachan/ru.jpg (2MB) http://www3.telus.net/wlachan/rd.jpg (2MB)
Now is the weird part. I did some careful test on a 2D subject (aligned with bubble
level and shooting straight down at very close distance, about 0.6m) but there is no
trace of blurry edge/corner at all. Both sides of the picture look equally sharp, or
at least I cannot tell the difference.
http://www3.telus.net/wlachan/f11.jpg (2.8MB)
So what is going on? I have never noticed such interesting issue with my next widest
lens FA*24/2 which is pretty sharp down to the corners for scenery. I thought a lens
like this would perform worse at close distance, but it's not acutally??
Alan Chan http://www.pbase.com/wlachan
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