K10D Back focusing Issue

It's when the camera focuses the lens behind the point that it is supposed to be focusing on. Front focusing is the opposite.

What causes it is a more difficult question (that I dare not even begin to try to answer at the moment as it's such a complex and peculiar thing).

Back or front focussing is only a problem that occurs with the use of auto-focus (AF) lenses in AF mode.

If a lens/camera combination is back focussing (BF), when you use AF to fix the focus point, that focus point will be slightly behind (further away from) your intended focus point.

Front focussing (FF) is the opposite, the focus point will be in front of your intended focus point.

This problem is not limited to Pentax cameras/lenses, all makes suffer from it to some degree. The probability is that film cameras had the same issue, but we never new it.

On a K10D, you can make an adjustment that affects all lenses by the same amount. The K20D and K7 can hold individual adjustment data for up to 20 lenses.

This problem does not occur with MF lenses, or AF lenses in MF mode.

Back/front focusing can occur with manual-focusing when there is a misalignment with the focusing screen or sensor. Then what appears to be in focus through the viewfinder is not in focus on the photograph.

There also can be an error with the focus confirmation system (the green hexagon indicator) sometimes in MF mode. This may be to do with misaligment of the sensor or AF sensor.

Back/front focusing with AF may have other causes, though sensor misalignment can be involved too.

Is this really true?

Given that you get focus confirmation when focusing manually, why might the actual point of focus not be different from where the camera thinks it's focused, and for the same reason as with AF?

In that instance Chris we would still be using the AF system to confirm focus.

If the camera's collimation is correct then using our eyes should get the right point of focus, subject of course to our ability to judge that point.

Don't forget other forms of focus aid, a split-screen not correctly spaced/placed also gives a faulty focus "comfirmation" and those are used with MF.

Quite - which is why I can't see why you wouldn't get the same BF/FF issues (if they're there in the first place) as with ordinary AF.

Well yes indeed. Judging it visually you wouldn't suffer from errors in the AF system.

I'm fortunate enough to have pretty good eyesight, but I don't think I can judge the focus point better than the AF system can - especially with long lenses where shallow depth of field makes it all so critical.

Is Stefan saying "yes it does" about Windows 7 or firmware 1.31.

My K10D is on v1.31 so do I need to "retro-install" v1.30 to use the Russian (or preferrably 'English' Pentax-Hack) Debug Mode invoker?

Peter

You don't need to use that at all. Just follow the instructions in my AF thread.


ETA: sorry just realised that 1.31 and 1.3 - whoops.

Try the modset.txt anyway. There's probably a txt file that does work on 1.31 if the modset.txt doesn't work

Actually according to this, unless you've got SDHC problems there's no need for 1.31

http://www.pentax.jp/english/support/digital/k10d_s.html

And according to this, MODEST.TXT doe still work with 1.31

http://forums.dpreview.com/forums/read.asp?forum=1036&message=35133375

Thanks for those Smeggy.

I had no issues with SDHC cards, but followed the logic that there might have been other small enhancements (unpublicised) in the newest firmware.

Got a shoot planned for tomorrow, so might try out the text file afterwards.

Regards

Yeah I always wonder about unpublished enhancements. Although it's always a gamble as you can also get new 'unpublished' bugs.

After some Googling, I've found this excellent and simple method by Ivan Glisin which works very well:

No need for 1.30. Do the following with 1.31:

In the root directory of your memory card create or copy a text file named

MODSET.TXT

with only one line in it:

[OPEN_DEBUG_MENU]

After inserting card back to the camera, to enable debug mode do the following:

1. Switch camera off.
2. Open card door and leave it open.
3. Switch camera on -- debug menu shows up.
4. Close card door.
5. Left/right to enable debug mode.
6. Press OK to confirm.
7. Go to Set-Up menu, go to the end and Set-up will change to TEST MODE menu, AF TEST option is there with Focus Corr inside.

To disable debug mode:

1. Switch camera off.
2. Open card door and leave it open.
3. Switch camera on -- debug menu shows up.
4. Close card door.
5. Left/right to disable debug mode.
6. Press OK.

Note: you can permanently leave MODSET.TXT file on your card.

Read more at: http://www.pentaxforums.com/forums/pentax-dslr-discussion/128474-need-k10d-firmw...#ixzz1DHfb0nZE

Yup, I leave my K10D permanently in Debug Mode ( after using the MODSET File/door open method. That way I can tweak the AF for different lenses.

Although now I've got a K-5 I will probably sell the K10D soon.