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Author Topic: Auto Focus micro adjusting  (Read 3001 times)
wmchauncey
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« on: October 13, 2013, 02:46:39 PM »
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I just had an idea that seems to work with my 1Ds MkIII...any reason that it wouldn't work with other micro adjusting systems?

AF microfocusing technique that lens using the tilted yardstick (with a piece of glowing duct tape attached as a focus point) method.
Take a series of images, each with a different microfocusing adjustment, it's easier if maintain them in order, like -3, -2,-1, 0, +1, +2, +3 then load them into layers in PS>select all>align layers>blend using stack method.
It then become a simple mater to select the correct adjustment number based on the produced masks.        Huh
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Fine_Art
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« Reply #1 on: October 13, 2013, 11:09:43 PM »
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Yes, it will work.
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wmchauncey
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« Reply #2 on: October 14, 2013, 06:26:09 AM »
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I like it because it takes the eyesight guestimation out of the process, especially when you want those eyes in focus at 40 yards.      Wink
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Ellis Vener
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« Reply #3 on: October 15, 2013, 10:10:32 AM »
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Of course it will work. Distance to target is important too. Canon and Nikon recommend 50x the lens focal length, while Michael Tapes (LensAlign target and FocusTune software inventor) recommends a  25x focal length distance. I've tried both and prefer the results using the 25x focal length distance.
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Fine_Art
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« Reply #4 on: October 15, 2013, 11:56:00 PM »
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Good tip, thanks.
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hjulenissen
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« Reply #5 on: October 16, 2013, 02:29:38 AM »
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The AF error _might_ depend on:
1. Distance
2. Aperture
3. Focal Length (if zoom lens)
4. Chosen AF point
5. Defocus method (is the focus moving in one or the other direction)
6. Temperature, moon phase and whatnot...

Further, you want to have some confidence in the readings (are your results just a random accident, or is it repeatable?)

If you are going to test all of these dimensions manually, you are going to have your hands full. I have been using Reikan Focal that automates the process to a large degree, I still find it to be tedious and "unpredictable" (if I find that one lens performs best at +4 in one test, then do a similar test 1 month later finding that it works best at -2, what does this say about the relevance of the entire exercise? What did I gain in terms of IQ during that month by using +4?)

-h
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Ray
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« Reply #6 on: October 26, 2013, 07:29:42 AM »
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The AF error _might_ depend on:
1. Distance
2. Aperture
3. Focal Length (if zoom lens)
4. Chosen AF point
5. Defocus method (is the focus moving in one or the other direction)
6. Temperature, moon phase and whatnot...

Further, you want to have some confidence in the readings (are your results just a random accident, or is it repeatable?)

If you are going to test all of these dimensions manually, you are going to have your hands full. I have been using Reikan Focal that automates the process to a large degree, I still find it to be tedious and "unpredictable" (if I find that one lens performs best at +4 in one test, then do a similar test 1 month later finding that it works best at -2, what does this say about the relevance of the entire exercise? What did I gain in terms of IQ during that month by using +4?)

-h

As I've mentioned before, I get the impression that this micro-autofocus adjustment is a minefield. I can't help wondering if the camera manufacturers have introduced this feature in order to solve their own problems of achieving good quality control. In other words, passing the buck to the consumer, whilst simultaneously creating a new industry selling  AF-adjustment targets and systems.
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Fine_Art
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« Reply #7 on: October 26, 2013, 01:17:15 PM »
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As I've mentioned before, I get the impression that this micro-autofocus adjustment is a minefield. I can't help wondering if the camera manufacturers have introduced this feature in order to solve their own problems of achieving good quality control. In other words, passing the buck to the consumer, whilst simultaneously creating a new industry selling  AF-adjustment targets and systems.

I agree it is a way to pretend tolerance errors are not a problem. As pixel densities climb the focus accuracy has to climb as well. This system lets them avoid having to improve.
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wildlightphoto
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« Reply #8 on: October 29, 2013, 09:26:32 AM »
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As I've mentioned before, I get the impression that this micro-autofocus adjustment is a minefield. I can't help wondering if the camera manufacturers have introduced this feature in order to solve their own problems of achieving good quality control. In other words, passing the buck to the consumer, whilst simultaneously creating a new industry selling  AF-adjustment targets and systems.

I agree.  IMHO on-chip AF systems as found on the Sony A7 & A7r will put DSLR PDAF and AF micro-adjustment in the dustbin of history.  On-chip AF isn't as quick (not yet anyway) but IMHO speed without accuracy is worthless.
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BartvanderWolf
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« Reply #9 on: October 29, 2013, 09:50:51 AM »
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I agree.  IMHO on-chip AF systems as found on the Sony A7 & A7r will put DSLR PDAF and AF micro-adjustment in the dustbin of history.

What some seem to confuse is, Auto-Focus Micro-Adjustment does not necessarily improve focus accuracy. It allows to remove a bias, thus reducing predominant front- or back-focus. Accuracy has to do with the type of AF determination, and/or sensitivity to low light and contrast levels, acquisition speed, and intelligence to anticipate/ignore motion.

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On-chip AF isn't as quick (not yet anyway) but IMHO speed without accuracy is worthless.

True, but accuracy without reasonable speed is, in many cases, also less than useful.

Cheers,
Bart
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