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07-08-2011, 09:43 PM   #1
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K-7 focus adjustment with 55mm 1.4

I recently purchased a 55mm 1.4 Pentax lens that I hope to use with my K-7. I did some quick and dirty tests for front/back focus under fluorescent lighting; I repeatedly observed the camera was back-focusing. I dialed in a +8, and this seemed to sharpen things up nicely. My question is this: can I expect similar results in natural lighting conditions? I tested it indoors first, rather than outside, for the simple reason that's probably the only place where I would shoot with it wide open. Any comments appreciated.

07-09-2011, 01:15 AM   #2
axl
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This is something that keeps puzzling me. I'm switching between +8, +9, +10 avery now and then. I wasn't bothered to check for specific light sources but that may be the cause...

Other thing worth pointing out is that all DA*55 owners report the need to adjust +5 and more. Often +8....
Makes one wonder...
07-09-2011, 04:03 AM   #3
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On my K-5 Silver it is +10 in daylight and +3 in red/orange tungsten light.

If it works, why worry?
07-09-2011, 04:09 AM   #4
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QuoteOriginally posted by axl Quote
Other thing worth pointing out is that all DA*55 owners report the need to adjust +5 and more. Often +8....
Makes one wonder...
From my experience this is true as well. For me, it's usually between +6 and +8, depending on the body.

07-09-2011, 12:07 PM   #5
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QuoteOriginally posted by dgaies Quote
From my experience this is true as well. For me, it's usually between +6 and +8, depending on the body
Do you calibrate every lens/body combo? I came to Pentax from a Nikon D80, and I never bothered with this micro-adjustment issue. To be honest, I don't even know if the D80 had this function available.
07-09-2011, 12:15 PM   #6
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QuoteOriginally posted by bushwhacker09 Quote
Do you calibrate every lens/body combo? I came to Pentax from a Nikon D80, and I never bothered with this micro-adjustment issue. To be honest, I don't even know if the D80 had this function available.
Ideally yes, at least for all your body supports multiple AF adjustments. The K20D, K-7 and K-5 support 20 lenses each, while the K-r has a single AF adjustment for the whole body (not individual lenses). Bodies like the K-x, K10D, K100D can be adjusted via entering the debug menu, but like the K-r this will be a single global adjustment. Generally speaking, if a lens has a FF/BF issue and needs a decent amount of adjustment on one body, it likely (but apparently not always) will benefit from a a similar adjustment on another body.
07-09-2011, 12:30 PM   #7
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QuoteOriginally posted by bushwhacker09 Quote
Do you calibrate every lens/body combo?
This is my strategie as well.
07-09-2011, 12:48 PM   #8
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My K-7/55mm 1.4 combo doesn't appear to need any adjustment in outdoor lighting, only under fluorescent lighting. I suppose I'll just have to decide where I'll be using this lens most, and go with that adjustment. I'm afraid I'm getting very close to "Rain Man" territory here--maybe the answer is simply picking up the camera and taking pictures without worrying about these focusing issues.

07-09-2011, 01:05 PM   #9
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QuoteOriginally posted by bushwhacker09 Quote
My K-7/55mm 1.4 combo doesn't appear to need any adjustment in outdoor lighting, only under fluorescent lighting. I suppose I'll just have to decide where I'll be using this lens most, and go with that adjustment. I'm afraid I'm getting very close to "Rain Man" territory here--maybe the answer is simply picking up the camera and taking pictures without worrying about these focusing issues.
Yes and no. While I generally agree it's best not to obsess over stuff like this, if you're shooting at or near f/1.4, the AF needs to be pretty spot in order to get good results.
07-09-2011, 02:26 PM   #10
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Yeah, I see what you mean. I'm almost afraid to test my 43 or 77.
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