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11-29-2011, 10:05 AM   #1
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K-5 Back Focus?

I did a search and didn't find anything much on this subject.

I just noticed recently that the lenses I've been using on my K-5 have been back focus by a lot! They all require a +8.

Lens used: 31mm ltd, 43mm ltd, 50-135mm.

Anyone else have this problem or just my unit?

11-29-2011, 11:02 AM   #2
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I had the same issues, then I downloaded the firmware upgrade (ver. 1.11, which you might have to find at the Pentax Japan site) and my back focusing problems were pretty much cured. I was then able to reset the camera menu settings back to zero for each lens. Give it a try. I've not tested each lens again to tweak it one or two points plus or minus, but my subjects look much more in focus on the computer screen.
11-29-2011, 11:22 AM   #3
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Well I don't see any problem if your lenses now are sharp the way you want it.

My DA*55mm/f1.4 nees +10 on my K-5 Silver:

Not to bad I think.
11-29-2011, 12:31 PM   #4
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While we are on the subject. If say my 500mm requires an adjustment of + 6 does that mean if my other lenses are also out, they will also be around + 6?

11-29-2011, 12:35 PM   #5
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QuoteOriginally posted by Bob from Aus Quote
While we are on the subject. If say my 500mm requires an adjustment of + 6 does that mean if my other lenses are also out, they will also be around + 6?
No, most of my lenses have different corrections.
11-29-2011, 12:52 PM   #6
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All my manual lenses require -10. The brand new Sigma 50mm f1.4 also requires -10. Very strange because the Sigma is all over the place... I just don't know.
11-29-2011, 03:30 PM   #7
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That's the thing, I'm not quite sure if even +8 is the right setting. I was setting the compensation on the go and it seemed like +8 made the image usable.

I have to find time to do a proper adjustment to see what the exact levels are.
12-01-2011, 04:16 PM   #8
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Has anybody else upgraded the firmware and then rechecked your findings?

12-01-2011, 05:01 PM   #9
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QuoteOriginally posted by Steve T. Quote
Has anybody else upgraded the firmware and then rechecked your findings?
I did upgrade the firmware to 1.11 and now my 43 requires a +5 instead of +8.

Has anyone gone back to 1.03?
12-23-2011, 11:10 PM   #10
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My 43mm limited needs +10 on my k-5.
In fact it needs a little bit more. And at 0 it's obviously out of focus. I think I'll write to them and see if there's any way to extend the range or tweak more.

Otherwise a beautiful camera and a wonderul upgrade on the K100D i've been using for years.
12-24-2011, 12:45 AM   #11
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Every camera and lens is different, it's a bit of a lottery.
Has to do with tollerances of the design and manufacturing, without it lenses and camera would become very expensive.

I had too return my sigma 30mm f/1.4 because it back focus so much -10 wasn't enough.
my other lenses are around and between + and - 6
12-24-2011, 01:53 AM   #12
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QuoteOriginally posted by Anvh Quote
Every camera and lens is different, it's a bit of a lottery.
Agreed, +9 on most of my M42s and anywhere between +6 - +9 for the newer lenses. The firmware upgrade made no difference that I could detect.
12-24-2011, 07:52 AM   #13
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QuoteQuote:
Agreed, +9 on most of my M42s and anywhere between +6 - +9 for the newer lenses. The firmware upgrade made no difference that I could detect.
Actually my M42 50mm Super Takumar focuses at 0 it seems. And the infinity stop makes it the sharpest lens I have.
12-25-2011, 08:35 AM   #14
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An update on my experience- On my 'puter, in MS Word, I went into the symbol library and pasted a couple black outline shapes (I think a star and an arrow), formatted them to have a pretty thin black line, stretched them out to be a few inches long on the sheet and placed right next to each other, and printed it on my laser printer. Then I hung it on the wall and systematically shot each lens at -10, -5, 0, +5, and +10, comparing the results on the computer screen. This is after my upgrade to 1.11. Where before I reported I was back to 0 without further testing (up from the negative settings I was at previously), my "further testing" revealed that I was pretty consistent at +5 showing the sharpest black line on the paper. If I was testing a zoom, I'd set the lens in about the middle of its focal length range. One or two of my lenses sat at other numbers. I have not taken the time to do finer testing than the increments-of-5 that I used, maybe if I get bored... I'm not sure if this was the best protocol, but it seems to have helped.

Here's a shot from the North Shore of Lake Superior from 2 weeks ago, after the above-mentioned testing. I was probably 125 yards or so from the subject (those crashing waves on the distant rocks). K5 on tripod, Pentax 55-300 at 190mm, F/8, 1/125 sec., ISO 100. Raw capture, processed in ACR, further sharpening applied in ACR, saved as both a 16-bit tiff for printing and as a >1meg jpeg, dumbed down even more at Photobucket. Cropped pretty much only to show a 16:9 format rather than 2:3.

More images from my visit to Lake Superior here- Steve's View of the World: Season's Greetings from St. Paul and the North Shore




My test target (it's full size), for the above lens, this was the +5 test image. All the test images were captured and viewed as raws, then viewed at 100% image size on screen in the Pentax Digital Camera Utility program, concentrating on the lines and line intersections. The outline targets proved more useful than the solid black triangle shape.

03-31-2013, 09:47 PM   #15
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How Do I Know?

I own the Super Takumar 28mm (58mm filter version) and Zeiss Flektogon 35mm F2.4. I've played around a bit with the +/- focus adjustments but couldn't see any difference. I have no experience being an engineer for Pentax or any other DSLR maker for that matter (which seems to be required these days). Can anyone help me regarding how I can best determine if corrective settings are required and whether it's +/-, or is it just try both and see which looks better?
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