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11-06-2010, 09:55 PM   #16
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QuoteOriginally posted by Wheatfield Quote
Dumb question, but you don't, perchance have a "protective filter" on that lens do you?
I thought about it.
All photos that is done indoor have been made without that filter. On the street - yes, mostly I put it on. But I tried to put it off and I did not see any difference. Now I cannot say which photos were done with or without it. So just right now I have gone to street and made some pictures without filter.

All photos have been done from fixed position (not hands) with manual focus turned into infinity.

street f1.8 - Pentax User Photo Gallery

street f2.5 - Pentax User Photo Gallery

street f5 - Pentax User Photo Gallery

I still see that offset red blur from cars' back lights and purple oreol around bright white lights.

On my 18-55 there is an interesting bug - if you set focus to infinity photos become smoothed. So to get clear pictures I have to set it to infinity and rotate back for a little.
I have tried the same trick with this 31mm but infinity is real infinity here.

11-07-2010, 01:46 AM   #17
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Your 18-55 doesn't have a bug. It is not uncommon to notice this on lenses.
A filter would made a difference for the light rendering but not that much for the sharpness.
I had this kind of crazy sharpness through a polrizer and a thick glass screen:

I would personnaly not use use the setting you have used (focus to infinity) for this kind of picture.

I found this other picture which may interest you. I get some purple fringing and AC around light spot at wide aperture at night which I think is normal.
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I would call Adorama to know what they can do in your particular case. Guess what? A DA-L 35 f2,4 with its coating made for digital may do a better job for you ^^
11-07-2010, 04:25 AM   #18
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To me most of the shots posted in your last two sets look infinity focus I don't expect much at f1.8.

P.S: A spectacular shot there Zav.
11-07-2010, 04:46 AM   #19
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I'm wondering why an infinity focus shot needs to be at f/1.8 - there surely will be better results gained from any lens if stopped down, esp. focusing at infinity.

11-07-2010, 05:17 AM   #20
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That is one amazing shot Zav!
11-07-2010, 11:14 AM   #21
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I have set focus to infinity just to emphasize this effect. I do not expect that these picture are sharp. But I expect that they should be uniformly bad.

But the same effect I can see even on close objects.
For example:

I see that all buttons have sharp left side and smooth right side. And I think that f2.5 should work on this distance and for this kind of photos.

Especially it is very observable on letters.

If we look at word "AVERTISSMENT :" (with double dots) we should expect that some of letter should be in focus. And some of them have enough sharp left side. But no one has sharp right side. And double-dots ":" in the end are awful.

To be sure that it is not related to light directition today I rotated camera 180 degrees and made a picture:

And double-dots show me that problems with lens does exist.

Intersing that if I set aperture to 3.2 then I can find enough sharp letters

but on the last letters that begin to be in out of focus area I see that bokeh starts on top of contrast area. I mean I would expect that if ":" just begins to be blur the "T" letter before ":" should be absolutely sharp. But it is not true.

Well, these all just my tears.

Zav, thank you for that picture - I really see the same purple areas around lights. But all your other lights have very right shape.

And the retile is veeery good. I like it )))

Yes, I will contact Adorama. And also (if Adorama does not have any great idea) I can try to go to Camera Co-Op in Houston and get to know if they can repair that lens. How do you think if it is good idea?

Last edited by Neco; 11-07-2010 at 12:25 PM.

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