This was my test with the DFA 100mm f2.8 macro on the K-5:

I focussed on the line 'However Nurse Todd' but the image would lead you to believe it was three lines up from that as it was back focussing.



After dialling in a +4 adjustment I got this:



Which is what I should have got the first time. It's that simple!

John K

Yes you would, or you certainly should be able to. You might even wish for a -2½ setting.

The software package would only take into account the shots taken during the test. So if it is an issue it won't go away.

Probably not long in itself, but you have to set it up, take those shots, sort out the folders import the shots, and then import them again. The software won't set the camera, you still have to do that yourself!

And you'll save a few $$££ into the bargain. Having set my 100mmm there is no way I'd wished to have that software solution, it really isn't necessary. Are you sure you have a lens that is out of AF adjustment? If you think you have then it is easy to fix it yourself. The software will not tell you what setting you need to enter into the camera to put the AF right, you'll still need to experiment to get it correct.

If you buy it and it doesn't help, I doubt you'd get your money back. Hear his comment as to why they don't do a fully functioning trial version.

If the newspaper / cornflake box method doesn't work for you, that software wouldn't help either.

John K

Try the newsprint/cornflake box method first. If you can get consistently good results after testing it that way having proved it was off before, what more do you require? The mission is accomplished.

John K

If the lens has an 'A' setting, then use that; the camera will then meter normally, use the camera to dial in the aperture rather than the aperture ring on the lens.

If it hasn't, have a look in the camera manual for 'E-dial in Program' (should be page 105.)
This shows how to set the camera to use the green button to give a shutter speed or aperture value automatically. If you do not have the camera manual handy you can download a copy from the Pentax web site.

John K

That does seem like a lot of work and I'm not sure you'd end up with a different result than if you'd used a page of newsprint or a cornflake box, especially if it has a word search puzzle on the back.
I'm sure that program was written by a former civil servant! Having to take shots in quadruplicate, then repeat the process even though the graph makes it obvious where the optimum is.
Perhaps OK if you have nothing else to do!

John K

Thanks. I will say though that my test was at full aperture, f2.8, so there wouldn't have been a shift of focus point. Another oddity, I repeated the test on the K-m with the 100mm macro and focus was spot on, not that I could do anything about easily it if it wasn't. Perhaps there were some quirks with the original K-5 that needed ironing out.

John K

JohnX, I'm as confused as you are!

John K
(Must be an issue only if your name's John )

Edit: I'd have thought more light / wider aperture, the better the AF functions.
Further edit: Could it be too much light overpowers the sensor or whatever it uses to ascertain the focus point?

Thanks for that link. I'm sure there is some good info there but the rough and ready cornflake packet serves the same function - the one I have has a word search on the back and that's just great!

What I am failing to grasp is how some lenses can focus OK on the viewing screen yet be out of focus on the sensor and hence need adjustment, but not others. I always use the centre point or focussing and check it visually as I would a manual lens so that is consistent.

I've just rechecked the adjusted 100mm DFA macro with the camera in manual focus mode and the adjustment I made holds good.

An explanation would be interesting and useful. If it was a camera issue and all the autofocus adjustments were consistent I'd understand, but that is not the case.

John K

I'll have to try it with the old lenses I was using then and see how they fare. Obviously no facility to correct them if they do need it!

John K

Thought I didn't have a problem but have just tried that and ascertained my DFA 100mm macro was back focussing by quite a bit. Have adjusted it to +5.
Then tried my 50mm FA f2.8 Macro and it is spot on without needing any adjustment!
What I cannot understand is that if the focus looks correct in the viewfinder, why isn't it what you get? Also how can different lenses vary in their fine AF adjustment requirements? This seems to be at odds with the whole SLR concept. I don't recall any talk of this issue back in the film camera days.

John K