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04-04-2012, 09:39 PM   #1
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New K-5 Quick AF Test

Hi all,

i just received my second K-5 body purchased during the sale before the price tsunami, and I thought it would be interesting to shoot a quick AF test before I upgraded the firmware from 1.01 to 1.13. Note that I made the same test with my first body, but the test was longer and tougher than this one (lower light and lower color temp).

The setup:


K5 firmware 1.01, FA 50 f1.4 @ f2.0., firmware 1.13 after, same lens, ISO, aperture and shutter speed.

All shots were taken after manually defocusing the FA 50 and letting the AF system find lock. The shots were also taken in 2 second timer mode with the SR system set to off.

LensAlign target on a light stand leveled with a bubble level.

Camera on my tripod also leveled with a bubble level, approximately 50x focal length from the target (2.5m).

I did not setup my tungsten modeling lights that I can dim to well below -1 EV and to about 2000k, but instead used one tungsten room light that I measured (using my Sekonic handheld meter) at EV 3.2 and 2490K on my Gossen 3f colorimeter. All measurements taken at the target face. The exposure times match EV 3 very closely.

The following is a crop where I set the AF fine tune to -10 as the target was completely out of focus out of the box at AF UNSET:



The image is clearly FF, but honestly, this is about equal to my K20 in this light, and would be just barely inside the DOF at the f stops I normally would shoot in this kind of light. I expect that it would have moved outside the DOF at EV -1. This is better than the 3 earlier K-5s I tried, which includes my third body, which I still own.

Next I upgraded the firmware and took another shot. I did not set the AF tune back from -10 and the image is seriously BF. It is a bit hard to tell, but the numbers towards the rear are sharper than the front but are still out of the front of the DOF and the black backdrop about 4" behind the target (which is cropped out) is in focus:



For this shot, I set the AF tune back to zero:



Please excuse the crop differences as I made no effort to crop them along the exact same lines (not important anyway). Regardless, the image is now just a bit FF, which a 2 or 3 adjustment would no doubt fix. I have no doubt that after the adjustment, the camera would hold DOF easily to -1 EV.

This is much better than my first body, which needed more AF tune than this. I could probably leave this alone and be just fine.

I know that others are not so lucky and have gotten K-5 bodies that cannot be tuned in. This post is not intended to disparage those issues or to disprove them. I had to do this work anyway to make sure my camera was ok (and I will need to tune quite a few lenses in the next few days), and also to backup my initial tests and results with the first body. In both cases, the focus shift to the rear after the firmware upgrade was very significant and easily corrected the amount of FF offset I had seen in 4 bodies, 2 before the firmware upgrade that I did not keep, and now 2 afterwards.

If anything, I hope that others can have a bit of hope that you can get a good K-5, or have it fixed if need be. This also reaffirms to me the fix that Pentax did to the system, which was claimed to not make any difference in at least one study published here.

Sensor stain check next and hopefully no buttons will fall off or mirrors start flopping (although my first body does "double-tap" now and again), and then out this weekend to find some spring wildflowers or something else to shoot. Lots of good glass holding down the shelf for too long lately.


Ray

04-05-2012, 12:43 AM   #2
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Given your testing thus far, I think you've gotten the perfect example of a K-5. Hopefully you don't run into one of those pesky issues(Gotta love the mount release button falling off...classic weird stuff!)
04-06-2012, 03:35 AM   #3
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After 1.13, AF Adjust OFF (C-4-26-1) works best for all lenses on my K-5. Did you check that configuration as a 'before and after'?

Cheers... M
04-06-2012, 05:07 AM   #4
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Original Poster
QuoteOriginally posted by Michaelina2 Quote
After 1.13, AF Adjust OFF (C-4-26-1) works best for all lenses on my K-5. Did you check that configuration as a 'before and after'?

Cheers... M
No, I did not, and of course, now I cannot.

I have quite a list of lenses, so I am quite sure that one or more will need a bit of AF adjustment anyway, especially since some are not Pentax lenses.

Ray

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