K5 Back Focus issue solved

Started Jun 10, 2012 | Discussions
sentro
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K5 Back Focus issue solved
Jun 10, 2012

So,

I've been having some back-focusing issues with My K5 and Sigma 180mm F3.5 lens. This was more pronounced with very small subjects. The AF Fine adjustment setting on the K5 can be adjusted between -10/+10 but that was not enough. So I put the camera in Debug mode via my PC and I did a global adjustment change for the max and min allowed....something like -100/+100. That did the trick. Look at these before and after pics. Good enough for me.

Pentax K-5
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PhotoHawk
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 10, 2012

Looks good. How did you put the K5 in Debug mode?

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sentro
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 10, 2012

Also, I caught these little guys hidding and took more pics.

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sentro
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Re: K5 Back Focus issue solved
In reply to PhotoHawk, Jun 10, 2012

PhotoHawk wrote:

Looks good. How did you put the K5 in Debug mode?

I found this app on the web...PK_Tether v0.6.5

I connected the camera, with the SD card inserted, and fired up the app. Once the debug mode is enabled on the camera and the required adjustments are done the Debug can be disabled from the camera itself.

So far it worked great with both my SIgma's...180mm and the 70-200mm F2.8

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Arijit Banerjee
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 10, 2012

Could you please expand on the actual workflow involved?
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sentro
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Re: K5 Back Focus issue solved
In reply to Arijit Banerjee, Jun 10, 2012

Arijit Banerjee wrote:

Could you please expand on the actual workflow involved?
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Arijit

Sure,

This is what it worked on my camera.

1. Run PK_Tether.exe (camera has to be ON and connected to your PC and have an SD card inserted) - The top LCD display on your camera will flicker.

2. In the software, on the top menu turn the Camera Debug Mode ON (at this time the top LCD light will turn OFF).

3. Turn camera Off and disconnect from your PC.

4.Turn camera back ON and go to Menu. Go to the C tab - Test Mode - AF Test. I set my value to +120um since my lens was Back focusing. I don't know what Area Test and AF Area number are so I left them at 0

5. Scroll down to Desbu Mode Disable and disable the debug Mode.
6. Turn camera Off and On again.

Now, when you go go custome function 26 (AF Fine Adjustment) it will still show + - 10 but it looks to me that now those values have increased quite a bit since my back focusing issue is now gone.

I hope this helps

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bkpix
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 10, 2012

Very cool!

What else can you do in debug mode?

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sentro
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Re: K5 Back Focus issue solved
In reply to bkpix, Jun 10, 2012

bkpix wrote:

Very cool!

What else can you do in debug mode?

Don't really know. To be honest I'm kind'a afraid to mess up with other stuff....don't want to mess up my favorite camera. Also, my K20 is in the shop so I don't want to be without a camera if i mess it up. Maybe some day when I'll fell brave enough......

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Arijit Banerjee
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 10, 2012

thanks a ton. will try this out for sure.
regards,

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Arijit

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muratscott
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 12, 2012

Hi Sentro,you've given me a nice idea to correct the focusing issue of my Tamron 17-50mm...The given limits of my Pentax K-5 's -10, +10 limits for focus correction is just not enough to cure my problem,so I have to give your prescription a try...

Thanks for the detailed step by step explanation...But I have a question : When you set the value to +120um under AF Test menu does it make a correction for all of your lenses or did you just mount your Sigma 180mm F3.5 lens on the camera and do the adjustments so that the camera would remember the sigma lens and and just correct the focus shift via the given parameter ( +120um).... Or do we have to able and disable debug mode each time we mount that particularly affected lens so that the focus correction of other lenses wont be disturbed? Because all of my other lenses focus perfectly on my K-5...I hope I could clear out my question in spite of my forgotten English.Thanks....

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sentro
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Re: K5 Back Focus issue solved
In reply to muratscott, Jun 12, 2012

muratscott wrote:

Hi Sentro,you've given me a nice idea to correct the focusing issue of my Tamron 17-50mm...The given limits of my Pentax K-5 's -10, +10 limits for focus correction is just not enough to cure my problem,so I have to give your prescription a try...

Thanks for the detailed step by step explanation...But I have a question : When you set the value to +120um under AF Test menu does it make a correction for all of your lenses or did you just mount your Sigma 180mm F3.5 lens on the camera and do the adjustments so that the camera would remember the sigma lens and and just correct the focus shift via the given parameter ( +120um).... Or do we have to able and disable debug mode each time we mount that particularly affected lens so that the focus correction of other lenses wont be disturbed? Because all of my other lenses focus perfectly on my K-5...I hope I could clear out my question in spite of my forgotten English.Thanks....

When I set mine I had the 180mm lens on however, this is a global setting. After you set this value you can then adjust each lens individually thru the AF Fine settings in the menu. The global value it just gives the camera some extra latitude for adjustment. So, now, when you give the camera a +10um that will be added to the global +120 value for a total of 130...I believe. It does seem to work fine for all my lenses so i will leave it to that.

I wish I knew what the other values are good for but I prefer not to mees with it.

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muratscott
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 12, 2012

Thanks for the info,very much appreciated...I've downloaded the firmware,connected my K-5 to the Pc and opened the debug mode...I've reached AF correction in the debug mode on the camera following your brief explanations step by step but I still am afraid to mess up with the precise AF values of all of my about 10 lenses including two FA primes .I've spent so much time for AF adjustment on each of them and I don't want to ruin it all...I'll do some more web search and then make an attempt to correct my Tamron...
Any tips and help are welcome...

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il_alexk
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Re: K5 Back Focus issue solved
In reply to muratscott, Jun 12, 2012

muratscott wrote:

... I still am afraid to mess up with the precise AF values of all of my about 10 lenses including two FA primes .I've spent so much time for AF adjustment on each of them and I don't want to ruin it all...I'll do some more web search and then make an attempt to correct my Tamron...
Any tips and help are welcome...

10 um in the debug mode is equal to 1 step in AF micro-adjustments; it should be easy to readjust your lenses without re-calibration.

You simply need to deduct the Debug AF correction value from all AF corrections of your lenses (divided by 10). For example, Debug AF correction of +40 is easily compensated with AF adjustment of -4.

This however implies some limits for the range of the AF corrections in the Debug menu. If you use too much of the correction in the Debug mode, you won't be able to compensate it for all your glass.

Say, all corrections for your lenses are within -2 to +4 range. This would limit the Debug mode corrections to be within the range from (-10+4)*10=-60um to (10-2)*10=+80um.

Enjoy and good luck.

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Cheers,
Alex

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muratscott
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To il_alexk...
In reply to il_alexk, Jun 13, 2012

Yes ,that was excatly what was making me worried of...It's almost impossible to compensate a huge front focusing lens with a back focusing one because of the limiting factor of the -10,+10 adjustment scale...I can calibrate a lens by going to -240 um in debug mode,but I can not calibrate my other lenses due to the limited scale with +10...As you've said I have to do it really carefully with planning the numbers first.Thanks for your help...

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JeffAHayes
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Re: K5 Back Focus issue solved
In reply to sentro, Jun 13, 2012

Oh yeah, man, that's A MAJOR difference! ^5 on figuring that out! Sure is great we can all post here and put our heads together. Without a forum like this, some of us might NEVER figure some of this stuff out!
Jeff
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DAVID MANZE
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Re: K5 Back Focus issue solved
In reply to JeffAHayes, Jun 13, 2012

Hi,

This test area/area number that comes up in mode debug may well be there to correct individual AF points independently,so for example if you have lenses that have a range of more than -10 to+10 one of the AF points could be programmed to be say, +40µ which would give you +4 additional compensation for a "rogue" lens. If you debug-adjust just, say,the extreme left point for +4,you could use that point uniquely for the problem lens without having to change the settings elsewhere!

This is just a theory and to be quite honest I've had enough AF checking with all my lenses to go down that road.

I think the debug mode is there so Pentax engineers don't have to disassemble a camera just for a calibration of the AF.
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il_alexk
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Re: To muratscott
In reply to muratscott, Jun 13, 2012

muratscott wrote:

Yes ,that was excatly what was making me worried of...It's almost impossible to compensate a huge front focusing lens with a back focusing one because of the limiting factor of the -10,+10 adjustment scale...I can calibrate a lens by going to -240 um in debug mode,but I can not calibrate my other lenses due to the limited scale with +10...As you've said I have to do it really carefully with planning the numbers first.Thanks for your help...

I hope you do have the warranty for your Tamron. The solution is obvious then

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Alex

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awaldram
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Re: K5 Back Focus issue solved
In reply to DAVID MANZE, Jun 13, 2012

DAVID MANZE wrote:

Hi,

This test area/area number that comes up in mode debug may well be there to correct individual AF points independently,so for example if you have lenses that have a range of more than -10 to+10 one of the AF points could be programmed to be say, +40µ which would give you +4 additional compensation for a "rogue" lens. If you debug-adjust just, say,the extreme left point for +4,you could use that point uniquely for the problem lens without having to change the settings elsewhere!

This is just a theory and to be quite honest I've had enough AF checking with all my lenses to go down that road.

I think the debug mode is there so Pentax engineers don't have to disassemble a camera just for a calibration of the AF.

There is an obvious difference

The debug adjust appears to physically alter the sensor positon , So as you surmise it stops the Pentax engineer having to drop the baseplate and adjust the AF module physical posiiton in relation to the sensor.

The user AF adjust seems to alter the compartator offset and has no bearing on the physical layout of the optical stream.

The obvious difference if these guesses are true is any adjustments in debug mode will not be compenasted for any heat or light value that may exist in the focusing algrorythm.

It is IMO a very risky strategy to fix a failing lens with this global physical body adjustment.

The debug adjust should really only be used to correct a global calibration error of the body.

I should also point out nowhere is the scale of the AF user tuning specified at 1=1um

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dcdrums
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Re: K5 Back Focus issue solved
In reply to awaldram, Jun 13, 2012

Very nice, thank you for the thread!!!

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merengues
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Re: K5 Back Focus issue solved
In reply to dcdrums, Jun 13, 2012

One of the best threads in a long time. Since I have a MAC, have to ask a friend to download PK-Tether for me. I have to make a general adjustment on my K-5 of +100um since all my lenses need +9 or more on the AF Fine Adjustment.
To everyone: Keep up the good contributions!

Earl

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