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Archive 2009 · Micro-adjustment
  
 
mweddle
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p.1 #1 · Micro-adjustment


I was wondering, I'm familiar with the micro-adjustment as far as the +/- adjustment, but what do these adjustments translate to as far as actual physical measurements? Does it depend on the focal length, or is there some kind of standard measurement that these numbers represent?


Dec 15, 2009 at 05:50 PM
mweddle
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p.1 #2 · Micro-adjustment


No one knows?



Dec 17, 2009 at 04:33 AM
jerrykur
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p.1 #3 · Micro-adjustment


Canon says they are just relative numbers.


Dec 17, 2009 at 04:42 AM
Ron Hole
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p.1 #4 · Micro-adjustment


Reminds me to ask, I have a lens that back focus's, do I add a "+" adjustment or do I add a "-" adjustment.

thanks



Dec 17, 2009 at 05:51 AM
Netgarden
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p.1 #5 · Micro-adjustment


FF- minus
BackF - plus



Dec 17, 2009 at 06:04 AM
Ron Hole
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p.1 #6 · Micro-adjustment


Thank you. The manual lost me and I had inclusive results with "random" settings.


Dec 17, 2009 at 06:08 AM
Dave Jr
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p.1 #7 · Micro-adjustment


The manual says: minus (-) shifts the point of focus forward, and plus (+) shifts the point of focus backward. So, if you have front focus, you would use plus.

My 70-200 had front focus on the 7d, and using +6 fixed it, so my own (limited) experience is: FF use + (to shift point of focus backward), BF use - (to shift point of focus forward).

Linda, this is the opposite of what you posted, please let me know if I have this wrong.



Dec 17, 2009 at 03:13 PM
SLD
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p.1 #8 · Micro-adjustment


Netgarden wrote:
FF- minus
BackF - plus


Wrong...

"-" to correct Back Focusing

"+" to correct Front Focusing



Dec 17, 2009 at 03:21 PM
SLD
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p.1 #9 · Micro-adjustment


Ron Hole wrote:
Reminds me to ask, I have a lens that back focus's, do I add a "+" adjustment or do I add a "-" adjustment.

thanks



You need "-" MA



Dec 17, 2009 at 03:23 PM
AGeoJO
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p.1 #10 · Micro-adjustment


I don't remember what the manual says.... and I know it confuses a lot of people but on the 7D Canon inserted two icons on that CF III - 5 display; "mountain range" and "camera" with the default setting "0" in the center. So, if your lens front focuses, you want to adjust it to include some "back focus setting", you dial in the mark towards the "mountain range" icon, which happens to be in the "+" range. And, of course, the opposite goes if your lens has the tendency to back focus.


Dec 17, 2009 at 03:31 PM
 

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gfiksel
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p.1 #11 · Micro-adjustment


AGeoJO wrote:
I don't remember what the manual says.... and I know it confuses a lot of people but on the 7D Canon inserted two icons on that CF III - 5 display; "mountain range" and "camera" with the default setting "0" in the center. So, if your lens front focuses, you want to adjust it to include some "back focus setting", you dial in the mark towards the "mountain range" icon, which happens to be in the "+" range. And, of course, the opposite goes if your lens has the tendency to back focus.


That is correct. '+' shift the focus away from the camera. "'-" shifts the focus back, towards the camera.



Dec 17, 2009 at 03:54 PM
Photon
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p.1 #12 · Micro-adjustment


Also, Chuck Westfall has described the MA adjustment numbers as relating to a proportion of the depth of field (or depth of focus?), so it is clearly different from one lens to another, and you can't dial in a MA by referencing a front or back focusing amount (which would vary with the object distance anyway).


Dec 17, 2009 at 04:05 PM
Vancouver47
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p.1 #13 · Micro-adjustment


Canon MA adjustment of 1 = 1/8 DOF

Page 21
http://www.usa.canon.com/uploadedimages/FCK/Image/White%20Papers/EOS-1D_MarkIII_WP.pdf



Dec 17, 2009 at 04:12 PM
Dave Jr
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p.1 #14 · Micro-adjustment


I just received a 7d, so have not messed with micro AF before. I've read a lot of different opinions on methods to use. Some say to test near the lens MFD, others say 25 meters. Another tip I found was to use the silent 2 setting when testing.

I'd be interested in hearing from people who have had consistent results using a particular method, and the details of that method.



Dec 17, 2009 at 04:33 PM
AGeoJO
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p.1 #15 · Micro-adjustment


Dave,
I would try to do the micro focus adjustment using the approximate distance you think you will be using the lenses for. For example, if you have lenses ranging from 85mm to 135mm, typically used for portraits, I would recommend adjusting/calibrating those lenses at portrait distances, somewhere between 3 feet and 10 feet or so. Long lenses for wildlife may benefit more from adjustment at longer distances, of 30 feet or greater. Zoom lenses? I normally do it a the long end and short end and the results I got are pretty consistent. The way I do it, if push comes to shove, I would put the setting more a tad on the front focus side. Since in real life conditions, you don't use your lenses wide open all the time and by closing the aperture, you will get a little more depth-of-field from the focus plane anyway.

One thing, I learnt from messing with the micro focus adjustment for over a year. Slant targets, like a ruler at 45-degree angle may result in inconsistency of the AF feature. I would strongly suggest to use targets that are parallel to the camera. Books or DVD cases arranged in staggered position of varying distance from the camera would be fine. I don't have any relation with LensAlign whatsoever but that device works great and I could repeat the microfocus adjustment with consistency. It is not cheap however .

Hope this helps,
Joshua

Edited on Dec 17, 2009 at 04:58 PM · View previous versions



Dec 17, 2009 at 04:51 PM
Dave Jr
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p.1 #16 · Micro-adjustment


Thanks Joshua. I also have difficulty using slanted targets, so, I generally use 3 batteries, staggered at an angle with enough space between to make sure the AF sensor points don't grab the wrong battery.

Are you supposed to use live view, regular AF, or both?



Dec 17, 2009 at 04:57 PM
Jack M
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p.1 #17 · Micro-adjustment


I just rented the Lensalign pro from lensrentals.com, takes all the guess work out of it. My 1dmkII was good with all my lenses, the 7D needed some adjustment, the worst being +4 on the 70-200 the best was the 24-105 and 400 5.6, they needed no adjustment.


Dec 17, 2009 at 05:09 PM
AGeoJO
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p.1 #18 · Micro-adjustment


Batteries are fine, too, I guess but I would use more than 3 batteries though. I used to use 5-7 books/DVD cases since their surface is flatter. You need to make sure that your objects are, as much as possible, parallel to the camera. So, if the camera is too low, for example, you cannot just tilt it up but you want to raise the level of the camera on the tripod. The 7D has that pitch and tilt display (push the info button twice and it will come up) to help you make the adjustment. That's the tough part and LensAlign makes your life easier in this respect.

I use LiveView to make the adjustment. Push the AF button and the AF will be adjusted and the result display. Rotate the AF ring on the lens to the infinity, push the AF button again and look at the AF accuracy. Rotate the AF ring to the closest focus distance, push the AF button again and assess the AF accuracy. You can take images each time and view them on your monitor. I normally use the 10X "loupe" of the LCD. Again, using the LensAlign device, it is really clearly visible. I don't want to praise this device too much though and it is not cheap.

Joshua



Dec 17, 2009 at 05:13 PM
Dave Jr
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p.1 #19 · Micro-adjustment


Yes, good point, batteries are not flat. I'll use live view too.


Dec 17, 2009 at 06:10 PM
Photon
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p.1 #20 · Micro-adjustment


Vancouver47 wrote:
Canon MA adjustment of 1 = 1/8 DOF

Page 21
http://www.usa.canon.com/uploadedimages/FCK/Image/White%20Papers/EOS-1D_MarkIII_WP.pdf

Thanks for the link. On page 22 it specifies that one unit = 1/8 depth of focus, a good distinction to make, because we're talking about the tiny inaccuracies at the focal plane.

+1 for the advice to avoid angled targets. You can get accurate results with a high contrast flat target at a distance in the middle of the range where you most commonly shoot. Start with major adjustments (say +10 and -10), using live view to close in on the correct setting, and do small adjustments until you can't see any difference. Use your computer monitor to check the final choices. I recommend setting the focus at infinity before each AF activation, and you can also try starting at MFD to see if you get consistent results.



Dec 17, 2009 at 06:29 PM
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