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Archive 2009 · Micro Adjust - best system
  
 
nathanlake
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p.1 #1 · Micro Adjust - best system


I have seen three basic systems described for setting the MA. Has anyone seen any well done comparisons of the three systems?

1. Focus on the centerpoint of some angled target that has a measurement system built into it. Take a picture, view it, adjust the MA, and then take another pictures. Repeat as necessary.
2. Focus on a vertical target. Take 3 pictures one with MA +X, one at 0, and one at -X. View the pictures, select the sharpest image, and then take another set of two bracketing the MA value that produced the sharpest image. Repeat as necessary until you have found the best MA setting.
3. Focus on an specifc image displayed on a computer monitor and adjust for least aliasing effect.

Number 1 seems solid and the description I saw of it suggested that using number 2 has some technical issues that made it less accurate.



Edited on Jun 29, 2009 at 07:17 PM · View previous versions



Jun 29, 2009 at 06:19 PM
Todd308
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p.1 #2 · Micro Adjust - best system


I spent quite a bit of time with this recently as a new 1dmkiii owner, maybe others that have used the systems longer can add better long term additional info.

It seems that the MA depends on a lot of things, bright vs low light, the distance and focal length the lens is shot at. Just those three factors alone change the results of the ideal MA # from my testing, usually not by much but it does vary. That's without even changing methods of the analysis testing itself.

I did the "shotgun" approach and tried to average the results to get the best function over the widest range of use. Of course if I was a portrait photographer or all landscape I would bias the testing to what I normally shot, but i shoot a bit of everything.

I did the angled ruler thing, and adjusted for where I wanted my ideal DOF, recorded the results, in both low/high light, and at different focal lengths for zoom lenses. Both handheld and on a tripod.

I did the flat target at various distances, lighting and focal lengths, again handheld and on a tripod. Using both the bracketing method and also using live view to focus and shoot the target then using the AF and comparing the images and the distances on the lens reported.

Then I went outside and just shot things, again doing the live view to get the best manual focus image I could get and then shooting the same image with the AF, both handheld and on a tripod.

Honestly for my camera I found there was more variation most times in the lighting conditions than in distances or zooming over a lens. Focus would shift on the same target that was dimly lit or brightly lit. I know I've read that only bright light targets and tripods should be used but to me you have to test the system how you use the camera, and we don't always shoot on a tripod or in super bright light.

In the end most of the numbers across the testing were pretty close in the case of the same lens, for example my 24-105 ranged from +3 to +7 in all conditions, my 100-400 from -1 to +2, and my 50 1.8 from +2 to +4 So in most cases I just split the difference and called it good. All those lenses were previously calibrated by canon to a 30D. So it seems even canon's calibration has say 3-4 MA points of give in it.

The only odd one was my sigma 12-24 that was still pretty consistent but ended up being +14.

Perhaps one of the best things it shows is how well the lens is calibrated, for example one would expect the resultant MA #'s to be close if the lens has a good calibration across various distances/focal lengths. Obviously they are not going to be perfect but if there was a wide swing it might indicate the lens itself is badly calibrated and obviously the MA cannot compensate for that since you only get one value per lens.

So in the end perhaps what it does best is give the owner a more precise method of tunning the lens (assuming the lens is well calibrated) to the individual body. So in the past say with my old 30D you had two variables. Your body might range from say +/- 3 and the lens in acceptable calibration might be +/-3. Now you can at least adjust the body to be as good as it can be for the lens, but you can still have lens variation, and it can't compensate for a poorly calibrated lens, especially one that is not consistent in it's poor calibration.

In the end it's better than not having anything calibrated as in the past, but probably not as good as sending in your camera and all lenses to have them calibrated to each other. I think it can however show a poor lens that needs calibration when if doing the MA testing it's way out from the group such as my sigma is, or the ideal MA number varies a lot from test to test. Obviously they will never be perfect we know that lenses especially zoom lenses have sweet spots in both focal length and distance.




Jun 29, 2009 at 06:54 PM
Grantland
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p.1 #3 · Micro Adjust - best system


i used the monitor approach and it worked like a charm.





Jun 29, 2009 at 07:08 PM
Alek Komarnits
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p.1 #4 · Micro Adjust - best system


Ditto for me what Grantland using this monitor test for micro-adjust.


Jun 29, 2009 at 07:33 PM
abam
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p.1 #5 · Micro Adjust - best system


don't use an angled target.

chuck westfall's recommended method for micro adjusting



Jun 29, 2009 at 08:57 PM
retrofocus
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p.1 #6 · Micro Adjust - best system


Grantland wrote:
i used the monitor approach and it worked like a charm.


+1: I also used the monitor approach with a moire focus test chart. The only thing I am still quite not sure yet is if the recommended minimum distance between picture and camera is really necessary here, especially when you have tele lenses. Well, it definetely worked for everything below 200 mm for me.



Jun 29, 2009 at 09:43 PM
nathanlake
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p.1 #7 · Micro Adjust - best system


I appreciate all your input, but I have read most of what is readily available on all three. I have used all three. What I am looking for is someone that has done some type of sound testing of all three to see if one is better than the other.

The vertical target method seems intuitively the best.
The angled target seemed hard to get just right.
The computer monitor test never seemed to indicate that any lens needed adjustment.

My tests were quick and dirty and therefore not really the trustworthy.



Jun 29, 2009 at 09:53 PM
Todd308
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p.1 #8 · Micro Adjust - best system


I had not tried the monitor testing method, so I tried it on three lenses this afternoon quickly and got the same results that I did when I did the other testing. I could have made a case for one lens being 1 MA different if I really wanted to find a difference, and that was the +14 sigma maybe being a +15 on the screen test, the others were dead on.

I guess to me, and I'm a scientist, it pretty well put my mind to rest that as long as you do some type of testing with a logical and repeated process under similar conditions it would seem they all give about the same results. If any of them was flawed I'd say it's the angled target. Not sure if this is due to the size of the AF sensor spanning too much of the angled target making inconsistent results or that you have to get very close with some lenses to get useful results.

I would imagine if you really wanted to decide a clear winner you'd need an optical lab. Honestly, for future lenses I'll be using the monitor method and then verify with real world objects from there. I did hours of testing over 3-4 days to do the shotgun approach with various approaches to get my averages and in the end maybe an hour with the monitor approach gave the same results.



Jun 29, 2009 at 10:25 PM
Nieuport N28
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p.1 #9 · Micro Adjust - best system


what's the best approach with a zoom that hits the focus point right on the money at the long end, but needs -3(actually -5) to hit the point at the wide end?

best conclusion was to set at -3 as it seems to be a good average to get much more consistent "in focus" shots at the wide end. the long end is still very sharp, but looks like it is not giving the 1/3 to 2/3 depth of field.



Jun 29, 2009 at 10:52 PM
retrofocus
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p.1 #10 · Micro Adjust - best system


nathanlake wrote:
The computer monitor test never seemed to indicate that any lens needed adjustment.

My tests were quick and dirty and therefore not really the trustworthy.


Yes, I made the same experience when I first used the moire monitor test screen. The differences are not easy to detect - you need to zoom in using LiveView on your camera screen. I always did bigger micro adjustment steps before (e.g. starting at -5, -10, -15), then preselect which one was better than zero microadjustment, and then using steps in between to finalize. With the moire pattern on the screen, you best focus on the circles around the spots - does the number decrease (more unsharp) or increase (sharper). The more details you see, the better/sharper.
My prime lenses were all spot-on, but especially my wide angle zooms needed minor adjustments at the wide end where I normally use them.



Jun 29, 2009 at 11:00 PM
 

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Todd308
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p.1 #11 · Micro Adjust - best system


Yeah that seems to be the best idea, unless you knew you were shooting say 75% of your pics at one end or the other then you might bias to that end. That is simply a lens variation issue, and the only way to fix that is to have it calibrated, and even it's hard to say what canon's acceptable range is for zoom lenses so it might come back the same. I'd be willing to bet almost none of the zooms are exactly identical in their focus across their whole zoom range, most will vary some. Another fix would be to have the ability to set different MA's for various focal ranges of a single lens. I would not be surprised to see this implemented down the road.

I know my 24-104L lens had that issue it was pretty well the same from 24-90 but at 105 it wanted an extra +1-2, I certainly biased that one for the 24-90 setting more than the 105 since it's rare I crank it to 105. The 12-24 sigma and 100-400 were very close in their zoom ranges. It's well known that most lenses are not as sharp at their extremes so it's no real surprise that they need a little more adjustment for perfect focus at one extreme of their zoom or another.




Jun 29, 2009 at 11:02 PM
Nieuport N28
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p.1 #12 · Micro Adjust - best system


thx Todd..............i know the 70-200f4 i had once was sharp at the long end, but backfocused at the wide end...Canon got dialed in a bit better, but was never perfect.

the variable MA you mention would be the ticket....



Jun 29, 2009 at 11:07 PM
UCSB
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p.1 #13 · Micro Adjust - best system


I've used all three methods. Although, I discarded the angled target immediately once I computed the correct distances (50x focal length or longer) required for micro adjustment ... plus the fact that angled AF tests are unreliable. I don't use angled target for any AF related tests at this point in time.

So that left the monitor approach or vertical target approach. I tried the monitor approach on my NEC 2690 monitor, but it has a polarized screen and I was not confident in the results I was getting with the moire test pattern. The monitor approach seems to work for some people, but maybe their monitors are a better match to the test pattern.

Now, I use this product and their recommended approach: http://www.precisioncaps.com/training_af_micro_adjust.html

This is a very accurate vertical target approach. You can 100% verify your MA results. There is no confusion or problem seeing exactly what is going on. Which, for me, lead to complete confidence in the results.



Jun 29, 2009 at 11:17 PM
timgangloff
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p.1 #14 · Micro Adjust - best system


this system looks like the most scientifically repeatable to me. looks pretty easy too.

http://www.bhphotovideo.com/c/product/628452-REG/LensAlign_LA_LAP_Lensalign_Pro_Focus_Calibration.html

http://www.rawworkflow.com/lensalign/



Jun 30, 2009 at 12:29 AM
UCSB
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p.1 #15 · Micro Adjust - best system


timgangloff wrote:
this system looks like the most scientifically repeatable to me. looks pretty easy too.

http://www.bhphotovideo.com/c/product/628452-REG/LensAlign_LA_LAP_Lensalign_Pro_Focus_Calibration.html

http://www.rawworkflow.com/lensalign/


The small size of the system prevents you from calibrating your lenses at the distance recommended by Canon (ie. 50x focal length or longer).



Jun 30, 2009 at 12:40 AM
abam
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p.1 #16 · Micro Adjust - best system


i certainly mean no disrespect to anyone in this thread, but there is no reason to pay a snake oil salesman for a micro adjustment "system" (which can essentially be replaced by printing out, e.g., a 1951 USAF chart for free and taping it to one's wall/window/door), especially one that uses elements that are specifically cautioned against by canon (i.e., angled charts; see the chuck westfall tech tips link above for details).

getting perfectly "scientific," repeatable, verifiable, reliable, etc. results depends on how you perform your MA, not on whether you paid for a fancy target or not (unless, of course, you're using an angled target, in which case you're repeatability/verifiability/scientificishness will be decreased).



Jun 30, 2009 at 12:59 AM
John_T
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p.1 #17 · Micro Adjust - best system


Tried them all, including my own appropriate variation on the theme.

You may get in the ballpark, but you will discover there is no ultimate truth, Pinnochio's nose just gets longer or shorter.

The only truth seems to come out of the manual:

"It is best to make the adjustment at the actual place to be photographed. This will make the adjustment more precise."

So, using the measurbation basic adjustments as a starting point, I plink around at my actual location to see if they need refinement. Usually no further adjustment is needed, though sometimes plus or minus 1 to nail it.







Jun 30, 2009 at 01:29 AM
dave chilvers
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p.1 #18 · Micro Adjust - best system


I tried all the known methods and in the end came to the conclusion that you need to check your lenses out in the field under shooting conditions with various subjects and different distances, find a happy medium and then just take pictures.

I now use Mf lenses almost exclusively anyway and am convinced that a lot of the better IQ I get from them is partly due to me being in control of where I focus. At least I know if it`s wrong then it`s down to me. Youd be surprised just how good some of your lenses are when you manual focus them and more so using live view.
Of course I understand that certain subjects require instant focus the moment you see the picture developing so AF is then a must (sports shooters come to mind)



Jun 30, 2009 at 02:57 AM
timgangloff
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p.1 #19 · Micro Adjust - best system


For what it's worth, I have no monetary interest in the system I mentioned above. That being said...

However, from watching their videos, it does look like you shoot at a perpendicular target and the angled measurement tool is only to tell you how far forwards or backwards your actual focal plane is. You are not shooting at the angeled target. Sometimes it easier to condemn something than actually look at it and see if it might be of some value.

Yes, you can shoot at a 1951 USAF Target, but what happens when you focus is not quite right. Is it front focusing or back focusing? How do you know other than trial and error? I think this is the crux of Nathan's original question.

I do think they are aware of the 50x limitation of the system and from what I've read, they are trying to come up with a different measuring stick for those longer telephoto lenses.

Personally, I've just always shot a bunch of images in the field (sports shooter) and then tried to determine if in general, it looks like I am back focusing, front focusing or right on the money and adjust accordingly. I don't think this method is very good though.



Jun 30, 2009 at 12:54 PM
UCSB
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p.1 #20 · Micro Adjust - best system


abam wrote:
i certainly mean no disrespect to anyone in this thread, but there is no reason to pay a snake oil salesman for a micro adjustment "system" (which can essentially be replaced by printing out, e.g., a 1951 USAF chart for free and taping it to one's wall/window/door), especially one that uses elements that are specifically cautioned against by canon (i.e., angled charts; see the chuck westfall tech tips link above for details).

getting perfectly "scientific," repeatable, verifiable, reliable, etc. results depends on how you perform your MA, not on whether you paid for a fancy target or not (unless, of course,
...Show more

Since you have a FF camera and four wide aperture primes, your are seeing only the easiest MA situations. There are many situations where MA is much more difficult (or time consuming) and where you can not get a clear result with a single test target on the wall. For example, MA on crop cameras is much more difficult because of the greater DOF. In addition, many lenses (ultra wide angle, f/4) will give you very unclear results because as you adjust your MA setting in one step increments you are just moving within your in focus zone.





Jun 30, 2009 at 08:15 PM
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