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05-27-2011, 10:50 AM - 1 Like   #1
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Pentax Kr before and after service

I thought I would post this for anyone who is having focusing problems with their KR and considering sending it to be adjusted. I bought my KR in March and noticed that focus seemed a little off. I’m not sure if it was exclusive to the tungsten FF issue, although it was more evident indoors. This may have been because outdoors I was using a higher aperture and in turn giving a greater depth of field that hid the focus being off.

I contacted Pentax customer service, and one of their suggestions was to use the Tim Jackson focus chart before sending the camera for repairs. I know everyone has seen a slew of these chart tests, but I think unless you happen to have a home optical lab, this may be the only way for a consumer to check the focus.

I set the chart up and followed the instructions. Camera on tripod at 45%, Center focus point, and used a shutter remote. I had the white balance set to AWB, and had the most recent firmware installed on the camera (1.01). I also did the exact same test using my Pentax DL.

Here are the results.

Pentax KR with DA 40mm @ 2.8 - AWB



Pentax DL with DA 40mm @ 2.8 - AWB



I decided to send the camera along with lens to CRIS repair. It took about a month to get the camera back, and the return process was rather easy. The CRIS website lets you check the progress of the repair online.

At CRIS they adjusted the camera to manufactures specifications. The repair invoice also noted updating the firmware, but when I checked it was the still 1.01. Maybe they just reinstalled it to get the factory defaults?

Here are the results of the repairs using the same test. Also I did the test using the tungsten white balance workaround suggested by pentax.

After Repair Pentax KR with DA 40mm @ 2.8 - AWB



After Repair Pentax KR with DA 40mm @ 2.8 - Tungsten white balance



The focus using tungsten white balance although not totally perfect is good enough for me. If I wanted to get it spot on I could set the AF adjustment menu to -3/-4.

After Repair Pentax KR with DA 40mm @ 2.8 - Tungsten wb -3 AF adjust



05-27-2011, 11:50 AM - 1 Like   #2
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I did the EXACT same thing as you. I went through the test charts, found that I had front focus (again I wasn't sure if it was a tungsten thing or not). A -10 on the adjustment wasn't enough to correct. I sent the camera to Pentax Canada (I included the photos of the FF and the test chart I used). I also sent the lens.

After 3 weeks I got it back and I repeated the tests. I now need only about -4 or -5 to correct the FF. At the time I only had the kit 18-55. Since then I acquired the DA 55-300. I repeated the test a couple of nights back with the 55-300 and basically got the same result, I need to use -4 or -5 to get it spot on. This leads me to believe that the the body was out of calibration rather than actually having a FF issue. I still need to repeat my test using a light other than tungsten.

I read this forum regularly (but post only every now and then). There are a couple of huge threads dedicated to this issue. I wonder off all the people that say they have FF issues, how many actually have cameras that are not calibrated properly? I know I thought I had a tungsten FF issue (as a -10 could adjust my focus enough). I posted charts on the other forum showing the issue. I started waiting for the firmware to fix. In the meantime, my e-dial started skipping (another common problem). So I sent in my camera to service. I thought, I might as well get them to check the focus. Sure enough it appears it was a calibration error rather than a tungsten FF issue.

So basically, I was complaining I had a tungsten FF issue when in reality I had a badly calibrated camera. Are others doing the same?
05-27-2011, 12:16 PM   #3
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Maybe but then you would think daylight or other photos would be off as well not just in tungsten

Good to see ppl are noticing improvements though after servcie, the FF issue does bug me with mine.

I wonder though, did they also adjust the lenses that were sent in?
05-27-2011, 12:26 PM   #4
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It is entirely possible that they only adjusted my kit and did nothing with the K-r. Maybe my kit was way out of tolerance.

The service slip did say "Auto Focus Sys Adjusted" so I would assume that they meant the body.

To bad I didn't have the 55-300 before I sent it in to compare.

AB

05-27-2011, 02:21 PM   #5
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After calibrating my own cameras, I believe test charts aren't reliable to start with. The camera could be adjusted to nail the chart properly but then the actual shootings could be way off. The reason is that as the lens focus toward infinity, the amount of actual glass/lens travel will decrease significantly. That means any AF error will show up more toward infinity. For example, moving the focus ring by 1mm near 0.3m has little effect on focus, but the focus will be totally off near infinity by turning the focus ring 1mm. This is not obvious through the viewfinder, but the full size picture will show. Also, tungsten environment is dim against daylight, and AF is just unreliable in low EV environment.

My own routine of testing and adjusting cameras (Pentax lenses cannot be adjusted other than infinity mark) is guessing the amount of um setting in debug mode and took a series of shots on tripod, then decided which um produced the sharpest results. I also pre-tested the lens on 40D with 10X LV so that I could determine how sharp that particular lens could be wide open. This is particular useful with wide angles. When the Pentax AF produced the same sharpness, then it's good.

Repeat the AF tests with different targets at least a few metres away. Let the camera AF from both infinity and closest marks. Redo the tests with different lenses until they agree on a common um. The interesting thing I have discovered is that some lenses are less prone to AF error, while some are particular worse, but usually standard prime is a good starting point. This will be a lengthy test but one that no test charts can replace. In fact, I would go so far saying test charts and monitor pattern tests are useless and give out false perception. At least this has been my finding since I calibrated my DS years ago, and still holds true when I calibrated my K-m last week. You can also flashlight the actual AF sensor underneath the mirror. If it's tilted (left-right) to start with, different lenses will probably suffer from different error I think because the light path is no longer straight/aligned.

Last edited by wlachan; 05-27-2011 at 02:40 PM.
05-27-2011, 03:06 PM   #6
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Same here, after service the front focus was significantly improved, but still an issue at wide apertures.
05-28-2011, 02:34 AM   #7
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I also sent my K-r to service and noticed improvements. Now there is a slight front focus which I am able to compensate with the af adjustment. The repair shop calibrated the af system and actually replaced my kit lens. So I guess some of my focusing problems was in the lens.

I have done some testing in different light conditions and there is a little bit more ff with tungsten light, but still well within what I think is reasonable.
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