Poll: AF Accuracy Adjustments

I believe they are cumulative.

Interestingly the new Canon cameras (5dMKIII and 1DX) enable af adjustment at both ends on a zoom lens.

Wonder if Pentax have introduced that with the K5II/S

I thought it was one or the other.

not 100% sure but I'm pretty certain I read that on Pentaxforums (although they may have been wrong)

Cumulative (otherwise surely it would be "Apply All unless you've done an Apply One" ).

There's a 'hidden' engineering adjustment value (that can be set by an engineer via the debug menu) that is applied first.
Next, the "Apply All" adjustment is added.
Finally, the individual "Apply One" is added (if set for the lens).

As I've said, my body was back-focusing quite badly and there were individual fine adjustments for my lenses. When the K5 had to go for a mirror-slap repair (mirror motor replacement) JPSS very kindly calibrated it to my DA*16-50 (and calibrated the lens too). It took several weeks to get repaired and calibrated, but the results are now like I have a new camera and lens combination!!

The other lenses now need less adjustment - but still some tweaking.

As has been mentioned: you do not need to worry at all about making AF adjustments!!! You can just reset it all if you feel like you're not getting anywhere

Matt

My limited understanding (from an AP article a while back) is that cameras and lenses are built within certain tolerences, for example -5 to +5 (made these figure up). Hence a camera at -5 and lens at +5 would be well out and need adjustment, but with another lens at -3, the difference may not be noticable. We are talking tiny amounts of measurements on the built of the camera and lens, but it does explain why some lenses may seem fine to one person but other people think its rubbish.

Hope this makes sense.

Regards

George

Are you 100% sure it's cumulative? Previous responses to the same question here and elsewhere said otherwise.

Now, as with the best AF adjust method, I'm totally confused!

...well, I can double check later and report back
Matt

Thanks Matt.

Just tried it...

And checked against the manual. It's a bit of a strange implementation, but I suppose there must be a reason. (It does allow you to quickly cancel all AF adjustments)

It is NOT cumulative (my mistake!)

When you select the AF Adjustment page there is a green arrow highlighting the setting that is currently being used. The manual says
It's the green arrow that shows you what's what

Doh! Feel free to throw rotten fruit...
Matt

The adjustment done via DEBUG using PK_Tether is cumulative and
100 on the DEBUG scale = 10 on the normal scale.

All my lenses seem to be 0 to -10 and beyond with some
old MF lenses so I might permanently set -100 in DEBUG

-

Whilst the AF adjustment is simple and easy to reverse, just don't be too quick to blame the camera/lens.

Testing my DA 300mm yesterday I was convinced it had some back focus. Just tested it again using a ruler, with centre focus box, exactly over the 75 line, as suggested on here on everything from -5 to + 10 and this was the best one.

[IMG]http://i393.photobucket.com/albums/pp15/chriseast/010_zps9f89f229.jpg[/IMG]

Adjustment on this one? 0

edit: Just noticed the although the ruler is perfectly in focus at the 75 mark with what appears to be perfect fade into OOF either side, the carpet is sharply in focus for the 2cm or so in front of the 75. Is that right - sort of thought it would be the 1cm either side of the 75 that would be in focus?

That might depend on how square you were to the ruler in the horizontal cross plane

Bernard

Hi Bernard

Thanks. Sounds a bit technical so I think I'll drop the ruler experiments and just take photos! Quite happy with some I took today, just need to practice.

Thanks

The ruler is above the carpet and you are looking at it at an angle so it would appear to be slightly in front of the 75 sue to parralax

Interesting results I think.

Now I'd like to know how many of those who voted "Never Checked", have now checked, and whether or not they have had to make any adjustments.