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05-11-2012, 06:42 PM   #1
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55-300 mm working OK?

I wonder if some of you more technically oriented folks could tell me if I have a problem with my Pentax 55-300 mm lens. In the photo below, Half Dome is about two miles away, and is in focus. But the mountainside behind it looks slightly out of focus to me, and it's about 3.5 miles away. I noticed in focusing on Half Dome that the focus ring was not quite at infinity. Later that evening I took a picture of the moonrise by setting the focus ring at infinity, since it was too dark to use autofocus, and noted that the moon seemed slightly out of focus, but maybe it's just a resolution issue.

About a week before this trip, I dropped the lens from 2-3 feet onto a hard floor. When I put it back on the my K-7, it seemed to work normally, but now I'm wondering.

Any thoughts?



05-11-2012, 07:15 PM   #2
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100% crops?
05-11-2012, 07:21 PM   #3
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Yes, 100%
05-11-2012, 07:59 PM   #4
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If thats a 100% crop, then your 55-300 just turned into a super DA* prime

05-11-2012, 08:52 PM   #5
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Sorry, I don't follow you.
05-11-2012, 09:35 PM   #6
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your da 55-300 is super sharp. looks like a prime lens quality.

Last edited by liukaitc; 05-12-2012 at 09:20 PM.
05-12-2012, 07:03 AM   #7
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Do this : go to tinypic.com and upload the original picture...put the link here, then we'll be able to see the 100% crop.
05-12-2012, 11:03 AM   #8
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In the surface, I don't see obvious problems, particular if that is a crop. Yes, DOF formulas might suggest the distant mountain should be within the zone when focusing on the near mountain, but those formulas are based on what would be "acceptably sharp" in a typical print viewed from a typical distance - not when pixel peeping. Also, it's normal that infinity focus would be not quite at the end of the focus range, so turning the focus ring to the end of its range actually focuses a little *past* infinity. Pretty much all AF lenses do that, to allow room for the focus mechanism to do its job and/or to account for shifts due to temperature variation.

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