[sebberry]

Your firmware updates are much appreciated by the community, but please include in one of them the ability to perform AF fine adjustments for both the wide and tele ends of a zoom lens. I'm tired of getting the lens set up just right with a focus chart in my living room at one focal length and then getting bird photos where the end of the log is sharper than the bird.

I had an awful time with my 50-135 at a recent concert. Some of the photos were perfectly sharp, others were completely unusable. There's too much variation between wide/tele, close/infinity for a single AF adjustment to be of much use.

Sincerely,
Mr. Frustrated :/

[Not a Number]

Note: Moved to Product Suggestions and Feedback

[pschlute]

I'm tired of getting the lens set up just right with a focus chart in my living room at one focal length and then getting bird photos where the end of the log is sharper than the bird.

Whilst I do agree that short/long AF/FA settings would be very handy for zoom lenses, I will point out that it is advisable to do your adjustments under the lighting that you intend to take photos under. If you are shooting birds, presumably outdoors, you should do your calibration in natural light.

[sebberry]

Note: Moved to Product Suggestions and Feedback

Thanks, I looked for that, didn't think to look under Help

---------- Post added 09-25-23 at 09:28 AM ----------

Whilst I do agree that short/long AF/FA settings would be very handy for zoom lenses, I will point out that it is advisable to do your adjustments under the lighting that you intend to take photos under. If you are shooting birds, presumably outdoors, you should do your calibration in natural light.

One thing I've never seen YouTube photography channel photographers go into is re-tuning their lenses every time they go inside to outside. Those wedding photographers must really struggle!

[ZombieArmy]

I wish the adjustment range was larger as well.

[UncleVanya]

Nikon's auto tuning feature would be ideal to dovetail with this.

[Lev]

Your firmware updates are much appreciated by the community, but please include in one of them the ability to perform AF fine adjustments for both the wide and tele ends of a zoom lens. I'm tired of getting the lens set up just right with a focus chart in my living room at one focal length and then getting bird photos where the end of the log is sharper than the bird.

I had an awful time with my 50-135 at a recent concert. Some of the photos were perfectly sharp, others were completely unusable. There's too much variation between wide/tele, close/infinity for a single AF adjustment to be of much use.

Sincerely,
Mr. Frustrated :/

I'm ready to pay for this feature!!!! It's a MUST!

---------- Post added 09-26-23 at 08:50 ----------

I wish the adjustment range was larger as well.

Will pay for this feature too

[BigMackCam]

One thing I've never seen YouTube photography channel photographers go into is re-tuning their lenses every time they go inside to outside. Those wedding photographers must really struggle!

Nonetheless, certain artificial light sources can affect AF performance. A few years ago I made the mistake of adjusting a couple of lenses in my kitchen one evening, with the overhead lights illuminating the room. They focused accurately until I took them outside the following morning. It took me a little while to figure out that the overhead kitchen lights were impacting AF Nowadays, when AF fine adjusting my lenses indoors, I always do this during the day, with plenty of natural light flooding into the room and no artificial light sources running...

[pschlute]

Nonetheless, certain artificial light sources can affect AF performance

I discovered this effect in the same way Mike, which is why I recommended it.

As an aside I once had a discussion with an ex-Canon technician who assured me it can make no difference ! Perhaps as the AF tech has evolved, and as we are likely to encounter very different light sources indoors than say 20 years ago, these factors come into play.

[sbc]

Your firmware updates are much appreciated by the community, but please include in one of them the ability to perform AF fine adjustments for both the wide and tele ends of a zoom lens. I'm tired of getting the lens set up just right with a focus chart in my living room at one focal length and then getting bird photos where the end of the log is sharper than the bird.

I had an awful time with my 50-135 at a recent concert. Some of the photos were perfectly sharp, others were completely unusable. There's too much variation between wide/tele, close/infinity for a single AF adjustment to be of much use.

Sincerely,
Mr. Frustrated :/

Same here for my 60-250. It is very sharp after a repair in Japan but the AF tunings for tele and wide are too far apart. I am hoping for a tele/wide AF adjustment ever since I bought the K-3III.
Every update has left me a little disappointed.

[Jonathan Mac]

I sold my 20-40mm Limited for just this problem - get it right at one end and the other end mis-focuses.

[sebberry]

I understand that AF fine adjustments are required because the AF sensor and image sensor are separated and the distance from the lens may be slightly off.

So here's my question - once the AF and imaging sensor distance differences are compensated for, why would each individual lens have different AF tuning requirements? And why is QC so spotty that lenses can focus well at one end, and be OOF at the other? That part completely confuses me - if driving the lens until focused, it shouldn't matter if it's at wide/tele.

[BigMackCam]

So here's my question - once the AF and imaging sensor distance differences are compensated for, why would each individual lens have different AF tuning requirements?

Because each and every lens component that affects the distance of the optical block or focusing element from the imaging and PDAF sensors is subject to miniscule but nonetheless significant manufacturing tolerances... tiny, tiny variances - microns - from specification (it's impossible to manufacture 1,000 of the same component to exactly the same dimensions so that there's not even one micron of difference). When these components are combined into a fully-assembled lens, the tiny variances in each one can have a cumulative effect.

I've had some recent personal experience of working with manufacturing tolerances - at a much coarser level, admittedly - in the design, prototyping and tweaking of some photographic products I'll shortly be selling commercially. The facilities I'm using to fabricate the components can achieve accuracy of +/- 200 microns, which sounds very small... but when multiple components of different dimensions, with cut-outs, holes for screws etc. come together, the cumulative offset from spec can be +/- 1mm or worse, rendering the product unfit for purpose. It has taken me hundreds of hours to end up with products that, aside from the basic designs, allow for and balance out the tolerances in each component such that every assembled product works as intended. It is a nightmare... and my products are hilariously simple compared to an autofocus lens I can't begin to imagine the tolerances they work to...

And why is QC so spotty that lenses can focus well at one end, and be OOF at the other? That part completely confuses me - if driving the lens until focused, it shouldn't matter if it's at wide/tele.

I'm less confident on this aspect, but I suspect it's to do with tolerances in the components that move - or limit the movement of - the optical block and/or focusing element. Again, tiny, tiny variances that add up when multiple components are combined. QC isn't spotty... it's simply the case that very few of the lenses coming off a production line will be subject to bench-test. If all of them were, the cost of production would sky-rocket, and you could probably double or triple the cost of every lens you buy...

This is nothing new, by the way... these problems existed in the film era too, but few (if any) people noticed them. It's only with the advent of high-resolution sensors and 1:1 pixel-peeping that we photographers can asecrtain small focus inaccuracies...

[pti-andy]

Your firmware updates are much appreciated by the community, but please include in one of them the ability to perform AF fine adjustments for both the wide and tele ends of a zoom lens. I'm tired of getting the lens set up just right with a focus chart in my living room at one focal length and then getting bird photos where the end of the log is sharper than the bird.

I had an awful time with my 50-135 at a recent concert. Some of the photos were perfectly sharp, others were completely unusable. There's too much variation between wide/tele, close/infinity for a single AF adjustment to be of much use.

Sincerely,
Mr. Frustrated :/

I second this wholeheartedly! Nearly all of my zooms differ in backfocus from the wide end to the tele end. Many other cameras have a Wide and Tele fine adjustment. Pentax should adopt this to keep PDAF/DSLR alive and compete better with mirrorless.

[sebberry]

I still can't figure out why, after fine-tuning, the camera doesn't just drive the lens until focus is achieved. Once compensated for during AF adjustment, in theory the image should be in focus on the image sensor when it's in focus on the AF sensor. Why would the image be in focus on the AF sensor but not on the image sensor?

(adding to the confusion is my 50-135 that's never in-focus in LV, but that's another topic )