[jmg257]

Nice explanation, but you did not get the question.

Whatever you do to your lens, will not change the AF sensor to image plane calibration. The AF sensor will focus the lens based on phase shift meaning that it compensates automaticlly for all the problems you mention abnove. What can be adjusted is the offset between AF sensor and image plane. So again why do some lenses reveal different fine adjsutments. Is there a feedback between AF and lens that results in something like an offset, Does the size of the AF area change too much for a given lens...
All the causes mentioned above will only change what you read off the foucs ring - who cares?

The camera will move the AF motor based on how far the AF module thinks the (lens) focus is out of phase (usually using the smallest defocus amount from the sensors, weighted per some complicated algorithms re:focus area, contrast & sensor type). The AF motor has encoder pulse feedback to the camera CPU to let it know how far the motor has moved. If the phase detected defocus amount being used is not within the "in focus" focus width, the CPU will calculate how many pulses it needs to see to drive the AF motor the right amount. So the motor encoder counts down, and eventually (hopefully) the next defocus amount is within the focus width, and focus lock can be indicated. The focus width is a range which the defocus amount can still be considered in focus w/regards to focus depth. This is a number that can get calculated based on various lens/focus info, and must apparently allow for some margin of error.

The AF motor has a mechanical connection to the lens focusing group...there are several gear blocks involved (in the body and the lens), and coupling points, and build tolerances, and maybe some backlash and other various built-in slop, and lots of different lenses to interface with. This means the CPU counts down how far the AF motor moves, without REALLY knowing how far the focusing group in the lens moved, or how exact it is positioned.

Besides normal factory differences, mechanical tolerances that otherwise should be tight and small enough to allow for quite accurate - & centered - calculations, may tend to get a bit sloppier when used and handled. Fine adjustment is provided to help compensate for these errors to dial in the exact target focus.


I imagine if BF/FF slop was so bad, the camera would never be able to find lock, except by luck - as any calculation determined/used to drive the AF motor would be off for the next go around.

Of course knowing EXACTLY what target the camera (with its large sensors) focused on is important too.

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Last edited by jmg257; 04-04-2012 at 05:31 AM.

[pgiguere]

Thx for your advice westmill I will put it to the test tonight with my K-5 to see if it makes a difference.

[xinawesome]

I manual focused on "4" I was on AF.s and the red light box flashed when I focused on "4"

[xinawesome]

[westmill]

If you want to see the size of yopur focus spot its rather simple. just put a black dot on a peice of white paper and see when your camera reacts. You will see that the centre spot cresponds and will zap into focus as the dot enters the two semi circles that marks spot metering.

[jeffshaddix]

Good luck with your returned K-5, my bet is it will be spot on.

[stormtech]

Thought I would update my thread here now that I have my K-5 back from CRIS.

First, I am very impressed with the service I received. Here is the time line of my repair:

Shipped to CRIS via Priority Mail on 3/26 after filling out the web form.
Received on 3/28
Camera inventoried on 3/29
Camera in repair on 4/3
Quality assurance 4/3
Repair completed 4/4
Shipped 4/4
Received by me on 4/12 (UPS is SLOW cross country!)

So for that part I am happy - it was in-house for only 5 days.

Here is what I wrote on the web form as my problem:

AUTO FOCUS PROBLEM. ALMOST ALL MY AF LENSES REQUIRE A +8 OR MORE OF FINE ADJUSTMENT TO FOCUS ACCURATELY. SOME OF MY LENSES WILL NOT WORK PROPERLY EVEN AT +10

And here are the repair notes on the work order:

WARRANTY
ADJUSTED AUTO FOCUS OPERATION. ADJUSTED WITH MASTER LENS.
INDIVIDUAL LENSES MAY NEED TO BE CALIBRATED TO BODY IF FOCUSING ISSUES REMAIN.
NO LENSES SENT IN WITH BODY.
CHECKED FIRMWARE
RESET ALL
CLEANED AND CHECKED TO MANUFACTURER'S SPECIFICATIONS

Finally had the time this morning to run it through some tests. I used my sharpest lenses - DFA 100 and DFA 50 macros - all the images are just fantastic in AF without touching the AF adjustment at all.

While I hated the fact of sending my camera off, I am so happy to have it back in perfect working order. I feel that CRIS did a great job and the turn around time was just fine.

Now off to play with my new DA* 60-250!

[derekkite]

Look on the net for a description on how phase detection works. Essentially you have light from the same point on your subject coming through the lens in two different places, each being reflected onto two sensors. When they are the same, you are in focus.

Assuming the body is accurate, a lens could have elements slightly out of alignment, and the two light streams could be out all the while the center of the lens is in focus. The phase detection method can calculate how much out of focus everything is. So if you enter an offset, it will correct.

[jeffshaddix]

Thought I would update my thread here now that I have my K-5 back from CRIS.

First, I am very impressed with the service I received. Here is the time line of my repair:

Shipped to CRIS via Priority Mail on 3/26 after filling out the web form.
Received on 3/28
Camera inventoried on 3/29
Camera in repair on 4/3
Quality assurance 4/3
Repair completed 4/4
Shipped 4/4
Received by me on 4/12 (UPS is SLOW cross country!)

So for that part I am happy - it was in-house for only 5 days.

Here is what I wrote on the web form as my problem:

AUTO FOCUS PROBLEM. ALMOST ALL MY AF LENSES REQUIRE A +8 OR MORE OF FINE ADJUSTMENT TO FOCUS ACCURATELY. SOME OF MY LENSES WILL NOT WORK PROPERLY EVEN AT +10

And here are the repair notes on the work order:

WARRANTY
ADJUSTED AUTO FOCUS OPERATION. ADJUSTED WITH MASTER LENS.
INDIVIDUAL LENSES MAY NEED TO BE CALIBRATED TO BODY IF FOCUSING ISSUES REMAIN.
NO LENSES SENT IN WITH BODY.
CHECKED FIRMWARE
RESET ALL
CLEANED AND CHECKED TO MANUFACTURER'S SPECIFICATIONS

Finally had the time this morning to run it through some tests. I used my sharpest lenses - DFA 100 and DFA 50 macros - all the images are just fantastic in AF without touching the AF adjustment at all.

While I hated the fact of sending my camera off, I am so happy to have it back in perfect working order. I feel that CRIS did a great job and the turn around time was just fine.

Now off to play with my new DA* 60-250!

Congrats! I'll be doing the same in June, but I'm using my camera too much to try it now.

[usmcxm35]

Found this thread because I wasn't sure how long it took CRIS to play with af calibration.
K-5 mailed on 5/16.
Arrived at CRIS on 5/18.
@Stormtech - how did you track progress, I couldn't find a way to do it on the CRIS website.
thanks.

[twitch]

I manual focused on "4" I was on AF.s and the red light box flashed when I focused on "4"

That is about the worst possible target to use when doing AF calibration to be honest, instead use a chart like the one in this link. Here's the link to the full explanation. Even better is "Lens Align" but it's not free.

[usmcxm35]

Talk about not free, its pretty steep for a ruler...

[rawr]

ADJUSTED AUTO FOCUS OPERATION. ADJUSTED WITH MASTER LENS.

Which is likely to be the FA 50 1.4, as per the AF configuration specified in the old K100D service manual:

[stormtech]

Found this thread because I wasn't sure how long it took CRIS to play with af calibration.
K-5 mailed on 5/16.
Arrived at CRIS on 5/18.
@Stormtech - how did you track progress, I couldn't find a way to do it on the CRIS website.
thanks.

When you fill out the web form on the CRIS website for your repair request, it automatically assigns a work order number to your case. You print a copy of the generated work order to use as a packing slip for your camera, plus when you go back to the site and log in, you are presented with that same work order showing the progress of your repair.

There is a link on their front page for "check repair status".

[usmcxm35]

I have the email from them, but the CRIS website asks for customer number, the is a PTX-######-#### number for the email but no customer number