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Author Topic: AutoFocus & AF Microadjust  (Read 507 times)
walter.sk
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« on: June 25, 2013, 04:43:03 PM »
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I'm about to use my Canon 5dIII's micro-adjust feature in conjunction with Lens Align and Focus Tune.  I'm concerned with my Canon 100mm f/2.8 macro lens.  I know that Michael Tapes recommends shooting at the distance we usually use, and since I use it overwhelmingly as a macro lens from its minimum focal distance to a few inches more, that's probably where I will set it from the Lens Align target.

What I am curious about, though, is when Canon manufactures these macro lenses does Canon optimize them for the closest focal distance, or for something akin to a non-macro 100mm lens's distance, such as Michael Tapes formula of 25X or 50X the minimum focal distance?
Again, I'm not looking for a recommended distance, but what distance Canon would use to optimize a macro lens as opposed to a non-macro lens of the same focal length.
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DaveCurtis
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« Reply #1 on: June 26, 2013, 03:25:01 AM »
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If you calibrate it to your 'normal' macro working distance, what Canon does doesn't really matter.

What matters is, that you calibrate your Camera/lens/AF.

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walter.sk
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« Reply #2 on: June 26, 2013, 12:30:20 PM »
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If you calibrate it to your 'normal' macro working distance, what Canon does doesn't really matter.

What matters is, that you calibrate your Camera/lens/AF.

My question was simply one of wanting to know what Canon does, independently of whether I calibrate the lens to my normal shooting distance or not.  Is that not a valid reason for wanting to know?
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Ellis Vener
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« Reply #3 on: June 26, 2013, 02:10:00 PM »
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Like any manufactured good  there is some 'range of acceptable deviation from standard with both the camera and lens. Unless they have changed it recently Canon generally recommends that if you use the AF micro-adjustment settings your target be at a distance equal to 50x the focal length of the lens  while Michael Tapes suggests that a 25x distance yields better results - but those are not for macro situations obviously. I do not know what parameters or how Canon tests the AF systems in sample lenses and camera bodies. Logically  they can't test every lens and every body they make because otherwise nothing would ever be able to leave the plant as every lens would need to be tested with every body they make.

You might try placing  the target close enough to fill the frame and see if that helps.

With Macro work, if at all possible I try to use Live view to focus with , using either the preview on the back of the camera or a remote live view screen / camera controller  for a smart phone. tablet, or computer. for that purpose I recommend the CamRanger , http://www.camranger.com
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Ellis Vener
http://www.ellisvener.com
Creating photographs for advertising, corporate and industrial clients since 1984.
walter.sk
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« Reply #4 on: June 26, 2013, 03:29:01 PM »
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Thanks, Ellis.  The Cam Ranger is one cool piece of equipment!

I ran my 100mm macro on the 5DIII through 2 sequences of shots and the sharpest shots came out at "0" on the microadjustment scale using FocusTune.  I used just a hair further than the minimum focusing distance.  Lucky, I guess.  Now to try my other lenses.
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