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Thread started 19 Mar 2013 (Tuesday) 17:58
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# What is your lens micro adjust technique?

Jun 15, 2013 19:36 |  #46

No, the correct answer is "to take median". You are confused with a totally unrelated fact: the 1/3 anf 2/3 DoF rule is about physical distance, but MA is not measured in feet or meters; it is rather measured in DoF units (8 MA units per one DoF step, according to info I saw on the web). Then median is exactly what you want - to be equidistant from the bad MA edges, in DoF units.

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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Jun 15, 2013 20:28 |  #47

pulsar123 wrote in post #16034537
No, the correct answer is "to take median". You are confused with a totally unrelated fact: the 1/3 anf 2/3 DoF rule is about physical distance, but MA is not measured in feet or meters; it is rather measured in DoF units (8 MA units per one DoF step, according to info I saw on the web). Then median is exactly what you want - to be equidistant from the bad MA edges, in DoF units.

You are probably right, but I doubt this is totally unrelated, as for every half DOF unit the physical distance double, the relation between DOF steps and distance is quite closely related.

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Jun 16, 2013 07:07 |  #48

Refill wrote in post #16034396
But with the DOF -1/3 +2/3 rule

What is the rule of which you speak?

Has it got something to do with the oft-repeated fallacy about Depth of Field being 1/3 in front of the subject and 2/3 behind the subject? If so, you do realise that this 'rule' applies at just one single focal length?

Frank Hollis - Retired mass spectroscopist
Give a man a fish and he'll eat for a day. Teach a man to fish and he'll complain about the withdrawal of his free fish entitlement.

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Jun 16, 2013 13:10 as a reply to  @ hollis_f's post |  #49

Anyway, I have been trying this Dot Tune method today with my 400mm f/5.6.

A real disaster! At f/5.6 I got -8 and +20 MFA as limits. I was curious and tried at f/11, results -6 +16. F/32? again -8 +20. There is a high variability on the limits.

I certainly won't take the median here, because

1.this lens was fine at 0 MFA
2. the MFA does NOT modify the way this lens focuses!

Yes, you read it right: no visible effect on this lens focus, whatever MFA setting I chose! What is happening here? Very strange. I had to tune one of my Sigma lens before, and I could see the difference, for sure! But here this method and the 7D MFA settings don't seem to change anything! I wonder what went wrong?

I had only the 400 and some manual focus lens, but I will try this Dot Tune method again with the Sigma, when I have some time to go out.

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Jul 20, 2013 04:20 |  #50

Interesting read, will give dot tune a try today

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Jul 22, 2013 09:42 |  #51

mitchrapp wrote in post #15738812
As pulsar123 stated, you have to use the nightlies.

Where to find the nightlies? I've looked all over their site, I find the nightlies for the 60D, but nothing for the 7D.

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Jul 22, 2013 10:54 |  #52

pulsar123 wrote in post #15734220
And dot-tune is now part of Magic Lantern - so the whole calibration is fully automatic (it takes 30 seconds to calibrate a lens). The word of caution - with any method you use, good light and good target make all the difference.

I used Magic Lantern "Nightly Builds" to get Dot Tune AFMA on my 5D Mk II. It works really well and is totally automatic. The Nightly Builds are not readily usable for the 7D or 5D Mk III and you have to go through a more complicated process to get them to work. I think it involves creating a "bootable" memory card and then writing some of your own code.

Before I start looking into how to get Dot Tune AFMA working on a 5D Mk III, does anyone know if it is even possible?

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Jul 22, 2013 16:01 |  #53

Unless I am reading it wrong, dot-tune was apparently added to 5D3 Unified build in March:

https://bitbucket.org …atform/5D3.113?​at=unified

Also, ChangeLog on the Nightly pages does mention 5D3, so I'm pretty sure the dot-tune should be there for 5D3:

http://www.magiclanter​n.fm/forum/index.php?t​opic=3072.0

7D seems to be there as well.

6D, Tamron 24-70 f2.8 VC, 135L, 70-200 f4L, 50mm f1.8 STM, Samyang 8mm fisheye, home studio

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Jul 22, 2013 16:02 |  #54

When taking focus distance into account, do you have to compensate for crop factor? For example, they recommend 50x the focal length you're testing. So if I want to calibrate a 28mm lens, do I have to do 28 x 1.6 x 50?

6D + 28-70mm f/2.8 L + Sigma 400mm f/5.6 HSM + 550EX

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Jul 22, 2013 18:24 as a reply to  @ lobby's post |  #55

Lensalign recommendation is 25xFL instead of 50x
https://mtd.tenderapp.​com …tool-when-using-lensalign
Kind of makes sense as it's easier to dial AF with shallower DOF, 50x is what recommended by Canon, kind of hard to find hallway that big to test tele lens.

They also have Distance tool to calculate distance for different FL and crop factor
http://www.whibalhost.​com/lensalign/ldt/inde​x.html

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What is your lens micro adjust technique?
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