[Cerebum]

I calibrated my 50-200mm and the improvement was stellar. I want to do all of them but it is a bit of a FAFF. Well, I began to wonder, would it be possible to calibrate a lens using focus peaking? If you had something fixed and graduated like a steel ruler, or for that matter, anything with a regular texture, my thought is you could focus the lens and live view would show you what is in focus and what isn't. From that you could see if it is front or back focusing without having to upload the image. So, the question is, would that work?

[pschlute]

I calibrated my 50-200mm and the improvement was stellar. I want to do all of them but it is a bit of a FAFF. Well, I began to wonder, would it be possible to calibrate a lens using focus peaking? If you had something fixed and graduated like a steel ruler, or for that matter, anything with a regular texture, my thought is you could focus the lens and live view would show you what is in focus and what isn't. From that you could see if it is front or back focusing without having to upload the image. So, the question is, would that work?

You are swapping one set of automatics (PDAF) for another (Focus Peaking). Nothing works better for assessing the accuracy of the PDAF system than the human eye. There is no need to upload photos. Just review them on the LCD at 100%.

[bertwert]

I believe I've seen that method mentioned in the past, as the live-view AF doesn't need to be calibrated in the same sense of PDAF. I've done something similar when checking the AF accuracy on my lenses.

[Wheatfield]

I calibrated my 50-200mm and the improvement was stellar. I want to do all of them but it is a bit of a FAFF. Well, I began to wonder, would it be possible to calibrate a lens using focus peaking? If you had something fixed and graduated like a steel ruler, or for that matter, anything with a regular texture, my thought is you could focus the lens and live view would show you what is in focus and what isn't. From that you could see if it is front or back focusing without having to upload the image. So, the question is, would that work?

I think you can check the focus accuracy of a lens to an extent doing what you say, but I'm not sure there is an easier way to actually calibrate the AF than the old school and, as you say, somewhat clumsy method we've been dealt.
I've found that I can zero in on accurate AF with not too many steps, most of which are done off the rear screen, but at some point, you want to bring the file up on a monitor and look at the pixels.
Here's what I do:
Set the AF offset to -3, then 0 then +3, taking a picture of a flat target a reasonable distance away. Target distance will vary based on focal length, if I am doing a wide angle, it will be fairly close, a telephoto, not so much.
Anyway, use the rear screen to see which is sharpest and repeat the test using that number as the center point. Drop the variance to -2, 0, +2 from the new center point.
Repeat the process, zeroing in closer to perfection. It shouldn't take very many steps to get there.
My last step is a -1, 0, +1 from my new center point. This one I put on a computer screen to pixel peep.
The most steps I've had to do using this method is three in camera and a final one on the computer screen.
Back in my days of running photo labs, this was called a ring-around, and was used for everything from helping to determine the aim point on a colour printer to setting the focus on lenses.
Hope this helps.

[hjoseph7]

You can send it out to these people, they probably will do it better than you or I can : Camera Lens Calibration Services - Canon, Sigma, Nikon, Sony & More! | Perfect Image Camera

I calibrated my 50-200mm and the improvement was stellar. I want to do all of them but it is a bit of a FAFF. Well, I began to wonder, would it be possible to calibrate a lens using focus peaking? If you had something fixed and graduated like a steel ruler, or for that matter, anything with a regular texture, my thought is you could focus the lens and live view would show you what is in focus and what isn't. From that you could see if it is front or back focusing without having to upload the image. So, the question is, would that work?

Maybe this helps? https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/

[Cerebum]

I think you can check the focus accuracy of a lens to an extent doing what you say, but I'm not sure there is an easier way to actually calibrate the AF than the old school and, as you say, somewhat clumsy method we've been dealt.
I've found that I can zero in on accurate AF with not too many steps, most of which are done off the rear screen, but at some point, you want to bring the file up on a monitor and look at the pixels.
Here's what I do:
Set the AF offset to -3, then 0 then +3, taking a picture of a flat target a reasonable distance away. Target distance will vary based on focal length, if I am doing a wide angle, it will be fairly close, a telephoto, not so much.
Anyway, use the rear screen to see which is sharpest and repeat the test using that number as the center point. Drop the variance to -2, 0, +2 from the new center point.
Repeat the process, zeroing in closer to perfection. It shouldn't take very many steps to get there.
My last step is a -1, 0, +1 from my new center point. This one I put on a computer screen to pixel peep.
The most steps I've had to do using this method is three in camera and a final one on the computer screen.
Back in my days of running photo labs, this was called a ring-around, and was used for everything from helping to determine the aim point on a colour printer to setting the focus on lenses.
Hope this helps.

Thanks for the detailed answer is the rear screen sharp enough? I will give this a go and maybe combine this with peaking and see what works best I admit sending it away should get the best results but by the time I have paid I could have used the money to buy that 20-40 limited, or at least that plm I am lusting after

[stevebrot]

would it be possible to calibrate a lens using focus peaking?

You can try, but my experience has been that even with magnification, focus peaking has poor precision.


Steve

[Wheatfield]

Thanks for the detailed answer is the rear screen sharp enough? I will give this a go and maybe combine this with peaking and see what works best I admit sending it away should get the best results but by the time I have paid I could have used the money to buy that 20-40 limited, or at least that plm I am lusting after

I've found that the rear screen isn't sharp enough to determine whats best at -1, 0, +1, but is OK for a wider ring-around. This is why I start with -3, 0, +3 and fine tune from there. I can do the bulk of the work on the rear screen, and just the final determination by going to the computer.
I shoot raw, so I do have to remember to set the file to jpeg just to speed up the process a bit.
Also, I've found it helpful to calibrate at what tends to be my usual shooting distance for a lens if it happens to be applicable.
For example, I will calibrate my new D FA* 85/1.4 at about 10 feet as that will be where it will see most of it's use (I hope).

[Cerebum]

Maybe this helps? https://testcams.com/blog/2015/09/22/dottune-autofocus-fine-tuning-in-under-5-minutes/

Oooh, that's neat thanks

---------- Post added 06-25-20 at 08:58 AM ----------

I've found that the rear screen isn't sharp enough to determine whats best at -1, 0, +1, but is OK for a wider ring-around. This is why I start with -3, 0, +3 and fine tune from there. I can do the bulk of the work on the rear screen, and just the final determination by going to the computer.
I shoot raw, so I do have to remember to set the file to jpeg just to speed up the process a bit.
Also, I've found it helpful to calibrate at what tends to be my usual shooting distance for a lens if it happens to be applicable.
For example, I will calibrate my new D FA* 85/1.4 at about 10 feet as that will be where it will see most of it's use (I hope).

Thanks

[Wheatfield]

Oooh, that's neat thanks

---------- Post added 06-25-20 at 08:58 AM ----------



Thanks

Yer welcome. If you try my suggestion tell me how it works out, and if you find an easier method along the way.

[Kozlok]

My process is to use focus peaking to get a value, then look at values +/- say 2 from that one with 6 photos at each setting (3 focused from near, 3 from far), and then I pick those based on eye on my monitors. It cuts way down on the iterations because I'm usually within 1 or so of the best choice.

[Wheatfield]

My process is to use focus peaking to get a value, then look at values +/- say 2 from that one with 6 photos at each setting (3 focused from near, 3 from far), and then I pick those based on eye on my monitors. It cuts way down on the iterations because I'm usually within 1 or so of the best choice.

What I like about what you are doing, it is something I don't do, and really should, is to take multiple samples. Thanks for the hint.

[pschlute]

You can send it out to these people, they probably will do it better than you or I can

Calibrating a camera lens combo is not difficult, but does require a disciplined approach. An external calibrator will not be able to do a better job than someone willing to put the effort in themselves. I have 14 lenses that I have calibrated. I would not pay $40 a time for someone else to do them all.

[Wheatfield]

Calibrating a camera lens combo is not difficult, but does require a disciplined approach. An external calibrator will not be able to do a better job than someone willing to put the effort in themselves. I have 14 lenses that I have calibrated. I would not pay $40 a time for someone else to do them all.

Heck, if you really want to, you can take a picture of a newspaper taped to a wall at each setting, see which one is best, and go back to the camera and input the appropriate offset that matches the sharpest picture. It does require some discipline, but there are so many ways to do it, each equally effective, that I really don't see why a person would bother with paying someone.
Pentax gives you all the tools you need to calibrate, built right into the camera as a user accessible adjustment. It's somewhat tedious, but it isn't especially difficult.
The only time I would get an outsider involved would be if I can't get a lens to calibrate because it is so far out of whack that there isn't enough offset. That would require a trip to the repair shop for the body and the offending lens.