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04-29-2014, 04:52 AM   #1
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K-5 AF calibration

A couple of days ago I bought a used Pentax DA* 16-50. I tried it out at the persons house and could see it was really sharp and I managed to whittle down the price and I bought it YAY !

Being all super excited the next day, I did some test shots to find the sweet spots at the different focal ranges. This lens is ridiculously sharp, and is the sharpest lens in my bag, every other lens I own is junk now ! I'm ecstatic about this lens, I wanna do cartwheels !

So just to be sure, I decided to check if it was back focusing and ...... it was ! But putting +10 in AF fine tune fixes it. Now I have a Sigma 10-20mm f/4 which I also realized was back focusing but it would need +11 or +12 to correct it. So I decided to test my 18-135 and ........ its back focusing too and +10 fixes it also. My FA 50mm 1.4 is not back focusing at all.

Tonight I've been reading as much as I can about this issue, and I'll admit, that I'm even more confused. Firmware hacks de-bug menu; removing bottom plates to get to adjusting screws; misaligned/displaced sensors, etc etc.

So what do I do ? Do I send my K-5 in for a calibration ? Or is there a DIY calibration like I've seen on a K10 where you take off the bottom plate and adjust a small hex screw ? Or is there a DIY Firmware adjustment ?

I think I should re-test the lenses again tomorrow to be thorough.

Whats the best course of action ?

(I've been struggling lately with the sharpness issues lately sorry team !)

04-29-2014, 05:50 AM   #2
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In my opinion, and with my experience, this is more a problem of lenses. Generally, fix focal lenses, are more accurate in focusing that zoom lenses. It's a problem that some zoom lenses tend to focus differently for different focal distances. So, if your 50mm focus right, the camera is OK.
04-29-2014, 03:45 PM   #3
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QuoteOriginally posted by JimmyDranox Quote
In my opinion, and with my experience, this is more a problem of lenses. Generally, fix focal lenses, are more accurate in focusing that zoom lenses. It's a problem that some zoom lenses tend to focus differently for different focal distances. So, if your 50mm focus right, the camera is OK.
So do I send the 16-50, 18-135 and Sigma 10-20 in for re-calibration ?
04-29-2014, 09:51 PM   #4
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You can send it. But as far as I know about optics, and my experience, zoom lenses are compromises. Some lenses focus closer at one end of their focal range, and farther at the other end. Also, there are lenses which will focus differently at different distances. Don't understand wrong, most times differences are small, excepting the cases when they are big If you read reviews on the net, you will see that many lenses has some percentage of misses. Also the cameras. They are not perfect mecanism.

So, after you send it to be calibrated, you will have to learn the strong points and weakness of your gears.

04-29-2014, 10:12 PM   #5
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QuoteOriginally posted by JimmyDranox Quote
You can send it. But as far as I know about optics, and my experience, zoom lenses are compromises. Some lenses focus closer at one end of their focal range, and farther at the other end. Also, there are lenses which will focus differently at different distances. Don't understand wrong, most times differences are small, excepting the cases when they are big If you read reviews on the net, you will see that many lenses has some percentage of misses. Also the cameras. They are not perfect mecanism.

So, after you send it to be calibrated, you will have to learn the strong points and weakness of your gears.
Okay then, it seems to be fine at the maximum +10 so I won't worry about it. But the Sigma is a problem, I'll send it in because its still under warranty. In future, I'll get extended warranties on my new gear. Looks like I've been lucky so far.
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