DotTune AFMA (dot_tune.mo)

[ArcziPL]

Is it correct that every time I start the camera, the scan range is set to Auto?

No idea but there is no reason you shouldn't stick to it. And I mean it as a person who usually hates all the "auto" stuff. The implementation of the auto algorithm is really smart. It combines ~binary search to find the coarse range with fine sweeping afterwards.

Try to rather not use the +/-100 mode as it sweeps with the step of 5, meaning that the final accuracy is only +/-5. The +/-20 method can also deliver a worse result than the auto if the values of +/-20 are still not beyond the borders of focus confirmation.

BTW, from my experience: I don't find the Dot Tune method the ultimate solution for focus problems. I'm used to still apply additional corrections based on photographing of real subjects and not focus charts. It seems to make a difference... Also the calibration distance matters as lenses can have an error depending on the it... But it's a good starting point and hopefully you don't have to play with the correction further, like I had to. Maybe I just have really bad lenses?

[c_joerg]

No idea but there is no reason you shouldn't stick to it. And I mean it as a person who usually hates all the "auto" stuff. The implementation of the auto algorithm is really smart. It combines ~binary search to find the coarse range with fine sweeping afterwards.

The auto mode takes only a very long time

Try to rather not use the +/-100 mode as it sweeps with the step of 5, meaning that the final accuracy is only +/-5. The +/-20 method can also deliver a worse result than the auto if the values of +/-20 are still not beyond the borders of focus confirmation.

I know that

BTW, from my experience: I don't find the Dot Tune method the ultimate solution for focus problems. I'm used to still apply additional corrections based on photographing of real subjects and not focus charts. It seems to make a difference.

The problem is not the method rather that the focus through the viewfinder varies greatly depending on the target.

The attached plot shows 10 shots of the Liveview focused and 10 shots of the viewfinder (Same chart). It is easy to see that the sharpness of the live view almost does not vary at all. The shots on the viewfinder vary very strong. The plot is the worst case with a Siemensstar. Shown is the relative degree of focus of an image determined as described here:
https://de.mathworks.com/matlabcentral/fileexchange/27314-focus-measure


My idea was: Comparison (with a script on PC) of an image that was focused on the live view with 21 shots that were focused in the range + -10 on the viewfinder. But here it was the same, after each test, the focus was different. You have to live with the fact that the focus on the viewfinder varies.

[rtr989]

I try to measure my 24-105L on two cameras 5D2 and 50D, i got the same results:
24mm = -5
60mm = +3
105mm = -1

measurements were carried out at the rate of 50 x focal lenght to target.
the difference is not linear and about 9 points at different focal lengths, but i can store only one digit in my cameras, i know in newest camera user can store data for wide and tele ends, but it also does not solve the problem completely.
Is it possible to make lens profile and track focal lenght in real time for change AF microadjustment data?