K5 Back Focus issue solved

Started Jun 10, 2012 | Discussions thread
awaldram
Forum ProPosts: 10,776Gear list
Like?
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

-- hide signature --

Dave's clichés

 awaldram's gear list:awaldram's gear list
Pentax Q Pentax K-3 Pentax smc DA* 55mm F1.4 SDM Pentax smc DA* 16-50mm F2.8 ED AL (IF) SDM Pentax smc DA* 50-135mm F2.8 ED (IF) SDM +11 more
Reply   Reply with quote   Complain
Post (hide subjects)Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark post MMy threads
Color scheme? Blue / Yellow