Lens Fine Tune Adjustment

AF fine adjustment is the menu you need. On yours it allows a different adjustment for each lens, while on older models it is a one-size-fits-all adjustment.

On a camera body with Live View (which we can take to be perfect for this purpose) then do the following:

1. On a tripod, use LV to focus on a specific clear object a few metres away. Like a poster on the wall.

2. Once focussed, place a mark on the focussing ring (or on a piece of masking tape on the ring) to show where the exact point of focus is in relation to the centre line.

3. Defocus the lens completely by putting your hand in front of it and focussing on that.

4. Focus the lens again using normal AF, rather than LV.

5. Is the mark you made in LV now exactly aligned, or is the focus point slightly different?

6. Adjust AF offset until the two match exactly.

Once done the normal AF can be set to match the Live View AF and you have exact focus.

There are charts for that for a simple test though you can use the newspaper for example, focus on a letter or piece of text and you'll see fast enough if the focus is spot on or not.

Live view focus in a different way, it actually use the final image as a way to focus so there is no focus error.
The phase AF (normal focus) works in a different way and is a separate device, so it can be a little bit out of line with the sensor for example.

Not if you use "catch in focus".
Any technique that use the AF phase might be needed to be calibrated to have the focus spot on.

No apologies needed

Thanks Km and Stefan, I will give this a try. I am pretty sure a couple of my lenses are out, especially the 10-20.

Just one more question.

How do you set it once you've worked out how much it is out?

Which camera do you've?
Only with the K20D, K7 and the K5 you can fine tune per lens with the other cameras you'll need to use the debug menu and with that you cna only fine tune the AF sensor meaning it will effect the AF for all lenses so you can't calibrate them seperately.

ps. live focus is always spot on so if the normal AF focus preciesly the same you know it's spot on.

I am going to set up my K5, the K7 I am selling soon. Any offers?

It's in the custom menu on the page/tab where the other AF orientated stuff is so out of my head.
You've two option, one is global adjustment and the other is adjustment just for the lens that's fitted.
The global adjustment has no effect on the separated lens adjustment so +6 global and +3 lens only doesn't make +9 for example.

I think I need to set up each lens individually....

Yes, that's the best but your camera needs to recognize the lens.
No problem with AF lenses but if you want to adjust some manual lenses then you need to use the global adjustment.

So, once you've used modset.txt to set AF adjustment, what next?

Is adjustment retained once you put another SD in the camera?

Many thanks Karma.

But I think that it is not worth the risk with the K10 focus, I defiantly do not feel confidant, and as its not an official Pentax option, plus I can’t afford a replacement camera, therefore I think that I will stick, as is.

That does not mean that I don’t truly appreciate your offer of help.

The upload problem is a sore point at the moment. As I tried to up load a couple of images to the (DPS), site of a camera mount/slide, I had made up for macro photography. The images did not upload, but that’s not the main problem. What ever I did has completely removed my folder of images. On the up side it did not remove the wife’s folder of images, that would have been curtains for sure.

What I am going to do now is to wait for the chap that does our house painting for us, to come and have a look, yes I know he is a painter, he is also very good with computers, and has images on a number of sites, so hope he can sort this “old fart” out.

Again many thanks for your offer of help, and your time taken typing your post, it really is appreciated.
Had a look at your gallery & Flickr, I do like b&w, takes me back a few years, when I had a darkroom, did mostly b&w then, made enough, to pay for all the equipment and materials. The past good old days, before those computer things.

Take care.

Chris R.

PS. Yesterday, I tried to change my gas account, to fixed tariff. British Gas, said it is easiest to do this on line, bad move on their part, whatever I did, locked up a part of their on line system, then had to do the change over the phone, that’s when I was told that I had locked their system. I think the two words -
“jinks and computer”, could be used.


Sorry for this post going way off topic.

The modset.txt file just instructs the camera to run the command(s) you put in the file. Debug mode stays enabled, until you disable it, so you can delete the modest file off the card and/or use another card no problem

Yes, the adjustment stays in effect, it is simply a camera setting.

Thanks guys, I'll give it a try then. Run out of adjustment on my K20D.

I'll need to check what my existing adjustments are, but I'm assuming I could make a global change that would create a new base-line that'll then allow me to use the normal in-camera adjustments?

ie if all existing are +, starting, say at +3, then I could create a new base-line of '0' at +3?

PS. For the brave (?) amongst us, here's how to make the adjustment mechanically http://ricehigh.blogspot.com/2011/02/hardware-adjust-pentax-dslr-for-af.html

IIRC , I did a global base line adjustment on my K20D. If you do, recheck all your lenses and not just add or subtract the numbers.

What a beautifully simple way to check! I have just run my K-x through this, and am relieved that the (centre spot) AF and the LV modes both focus at identical points. So I am one of the lucky ones.

The olique-test-card way of testing was not too precise with the 18-55 mm kit lens of the K-x. At maximum zoom the aperture is only f/5.6 so there is too much DoF to see much difference in sharpness over quite a big range either side of the focus target.

Thanks for this tip.

Martin