Debug mode on K20D - works nicely

There seems to be little concrete information about running debug mode on a K20D, so I thought I'd share that I tried it last night, and found it very straightforward.

I've always been irritated that my K20D has to be set to -10 for decent AF with my FA 50mm 1.4. What if -11 was the perfect setting? Well after playing with debug mode I'm now fairly convinced that -10 was in fact optimal, but I still prefer fixing the problem 'globally' through the debug mode (set to -90) and then fine-tuning slightly per lens if necessary, rather than having to go to the extremes of the standard adjustment.

Unfortunately the 50mm is the only fast lens I have, so I can't properly test how the -90 affects other lenses, but the other (slow) lenses I have seem to work fine at -90. So for the time being all my lenses are now 0 on the standard adjustment, and I'm fairly confident that future lenses have a better chance of working out of the box, without huge adjustments.

If there are any questions about the procedure feel free to ask. It's pretty low risk I think. It's not like you're modifying the software - you're just sending it a command (via a text file). From a software perspective it's no different than pressing a 'magic' sequence of buttons.

If there's any interest I could perhaps post a walkthrough with screenshots. Or maybe that exists somewhere already?

Haven't come across this myself, and would be very interested in more information, as I also feel a bit constrained by the current AF adjustment limits in the K20D.

Is there a debug mode for the K-7?

I don't think I need one, but it's interesting to know about such things.

I'd be interested in knowing a bit more about it Andy. Do you have to download software from somewhere or is it a key press sequence thing?

Yes there is. The basic procedure for all models is here:

http://www.pentax-hack.info/documents/debug.html

There's enough info there to try it out, but I'll look at putting together some (K20D-specific) AF-adjustment instructions over the next day or two.

Neither - you write a small text file to your SD card. The camera looks for the file on startup and reads it if it's there. The file contains commands - the only commands I tried are the ones to turn debug mode on and off.

So there are no downloads and this isn't a third-party hack. This is a mode that the Pentax engineers built into the camera software, presuambly for their use and/or Pentax support use.

Naturally there is some risk that the debug mode will let you do things that screw up your camera, but I think if you stick to AF adjustment and stay within reasonable limits the risk is low.

That definitely looks interesting. I'd be cagey about downloading intrusive software, but that's got to be worth a try.

Thanks.

There's also a good documentation out for using the K-x debug mode. (Haven't yet tried it myself though...) I know this might be different from the K20D, BUT in this documentation

http://deejjjaaaa.blogspot.com/2009/12/pentax-kx-debug-menu-to-do-focus.html

I would highly recommend to read point 14 - just in case that's the same on other Pentax models. So, if you try this at home, better make sure to document all subsequent changes to the AF adjustment

Thanks for this link - he actually used a different command than I did, though the end result is the same. I will have to try his way, to see if it works on K20D, as it looks slightly better.

Regarding the AF adjustments being cumulative, that is the same on the K20D, but it's not a big deal. You don't need to remember where you'd got to - the camera does that. So if you do -40, then do another -40, the camera will say -80 when you come back again a third time, so you know to do +80 to get back to zero.

Just tried it, and although this way looks a little more scary initially, it's more convenient because you just write the file to the SD card once, then you can easily switch the debug mode on and off through the camera. (The way I was doing it required the file to be changed to switch debug on and off)

The K20D details are slightly different than the Kx - I'll write it up and post a link.

I've written up the intructions for the K20D here:

http://www.andymcm.com/blog/2010/01/debug-mode-on-pentax-k20d-dslr.html

Thanks Andy. Good work.

Being a little thick, however, can I clarify something?

With the K20D you can adjust AF globally, ie applies to all lenses, or individually.

I've made AF adjustments individually.

This debug method seems to apply global adjustment.

Once the global adjustment has been applied via the debug method, does this effectively alter the start point for any subsequent individual adjustments?

ie If I use debug to set the camera to -20 will I then be able to individually adjust lenses in the range -10 to -30, ie +/- 10 either side of -20?

The thing that strikes me about this is that the global setting will be factory set against a known standard. We wouldn't know if a lens we selected conformed to that known standard, so we'd be setting our camera out of kilter more than likely.

If you sold that camera on, the buyer could be very disgruntled to find that their lenses were not focusing properly....

In any event, if the camera is so far off that the individual lens adjustment isn't enough, then something else apart from AF adjustment might be faulty, so I'd be inclined to return it for an engineer to fix.

Yes that's the basic idea, though the scales aren't the same, so the numbers aren't quite as simple as this. So setting the debug global to -90 might be equivalent to -10 on the standard scale, meaning that the new standard range would be -20 to 0.

Unfortunately when I went to confirm this behaviour this morning, I found that the focus on my FA 50mm 1.4 was wrong again. So I reset everything back to defaults, in the debug menu and the standard menu, and now it's focussing correctly at the defaults. This doesn't make any sense to me. I'll need to do a bunch more tests to work out what's going on.

You may get different AF accuracy with different subject distances. I don't like using test charts because that only tests at close distances.