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  #1  
Old December 26th, 2007, 07:23 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Default AF Micro-Adjustment tool

Hi folks,

Having acquired my 1Ds3 (wow, what an amazing tool), and having spend some time getting used to the controls and menu layout, I decided to calibrate my lenses using the AF micro-adjustment feature. I can tell you, it makes a huge difference in focus accuracy and repeatability.

I've made a simple tool to assist in the procedure, and you can download it here. It should be displayed on an LCD screen a 100% zoom setting (so at native size).

It works by exploiting the interference patterns or moiré between the R/G/B LCD elements and the camera's LCD elements when directly viewed with Life View. With good optics and perfect focus, the moiré is maximized. Depending on shooting distance, choose the Life View zoom setting (full, 5x 10x) that shows it best. When the situation permits, you will see larger R/G/B aliasing of the LCD elements. You'll also notice how narrow the field of focus is, especially with lenses that react strongly to small focus ring rotations.

This is my first version of the target, therefore I may update it with some other features, also depending on feedback. So let me know if it works for you, or what might help to make it better.

Bart

Last edited by Bart_van_der_Wolf; September 7th, 2015 at 05:24 AM. Reason: Updated the file link location
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  #2  
Old December 26th, 2007, 08:00 AM
Doug Kerr Doug Kerr is offline
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Hi, Bart,

That sounds like a very interesting approach.

Quote:
Originally Posted by Bart_van_der_Wolf View Post
It works by exploiting the interference patterns or moiré between the R/G/B LCD elements and the camera's LCD elements when directly viewed with Life View.
I'm having trouble visualizing the principle here. Are you saying that the moiré phenomenon lets the viewer better discern the sharpness of the image of the "focus target", or what? I'd enjoy being able to grasp a little better what chain of effects you are exploiting here. It sounds fascinating.

Thanks.
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  #3  
Old December 26th, 2007, 09:07 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Doug_Kerr View Post
I'm having trouble visualizing the principle here. Are you saying that the moiré phenomenon lets the viewer better discern the sharpness of the image of the "focus target", or what?
Hi Doug,

What happens as one manually adjusts the focus is that at the exact optimal focus setting the background will change from uniform gray into larger (colored) aliased dots when viewed on the camera's LCD. The circles and cross hair will allow to acquire AF easily, and when calibration is optimal, moiré will be maximized on the camera's LCD.

A procedure that works for me:
- I switch to LifeView, which in its current implementation will only allow manual focus.
- Optimize manual focus by searching for maximum aliasing. This will only occur a best focus (and assuming a decent enough lens is used), otherwise the defocus will act as a low-pass filter and prevent the aliasing.
- Switch off LifeView, and watch the lens barrel's focus indicator for the next step.
- Use AutoFocus (single AF spot) to focus on the (laptop) LCD screen, and watch the direction of adjustment. That will show whether the current AF calibration setting will front or back-focus.
- Apply an adjustment via the camera menu, and repeat the procedure. Once the adjustment is optimal, there will be no difference between manual and auto-focus.

The flat computer screen will prevent misinterpretation of the focus distance, because the AF system cannot react to phase effects from subjects at other distances. That makes it quite easy to get repeatable results. And because the computer LCD emits light, it can be easily done indoors, at common shooting distances for the lens to be calibrated for.

For super tele lenses it is probably easier (for distance reasons) to use a Zoneplate type of chart outdoors.

Bart
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  #4  
Old December 26th, 2007, 10:37 AM
Doug Kerr Doug Kerr is offline
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Hi, Bart,

Quote:
Originally Posted by Bart_van_der_Wolf View Post
What happens as one manually adjusts the focus is that at the exact optimal focus setting the background will change from uniform gray into larger (colored) aliased dots when viewed on the camera's LCD. The circles and cross hair will allow to acquire AF easily, and when calibration is optimal, moiré will be maximized on the camera's LCD.
How neat!

Quote:
. . . otherwise the defocus will act as a low-pass filter and prevent the aliasing.
Of course! What the moiré does is allow us to visualize the higher-frequency components in the image (just as many so-called "contrast detection" AF systems actually do), and of course they increase as the "low pass" effect of the defocus spread function declines.

This of course makes perfect sense as moiré is a visible manifestation of aliasing, which occurs from high-frequency components beyond the Nyquist limit for the system. Less HF content - less moiré.

Quote:
The flat computer screen will prevent misinterpretation of the focus distance, because the AF system cannot react to phase effects from subjects at other distances. That makes it quite easy to get repeatable results. And because the computer LCD emits light, it can be easily done indoors, at common shooting distances for the lens to be calibrated for.
Very clever!

Brilliant, my friend.

Best regards,

Doug
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  #5  
Old December 26th, 2007, 12:23 PM
Ben Rubinstein Ben Rubinstein is offline
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Sounds incredible, all I need now is for my 5D's to have had this feature! :-)
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  #6  
Old December 26th, 2007, 01:42 PM
Nicolas Claris Nicolas Claris is offline
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ABSOLUTELY brilliant Bart!

I sure will give it a try tomorrow…
For zoom lens like the Canon 24-70 what lenght would yoy choose for calibrating? 50 mm?
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  #7  
Old February 14th, 2008, 03:19 PM
Steve Febbraro Steve Febbraro is offline
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Quote:
Originally Posted by Bart_van_der_Wolf View Post
- Use AutoFocus (single AF spot) to focus on the (laptop) LCD screen, and watch the direction of adjustment. That will show whether the current AF calibration setting will front or back-focus.
So glad I found this forum, and the information on the micro-adust LCD chart and procedure.

I do have question however..When watching the direction of adjustment, looking down at the lens, does a leftward move mean the lens is backfocusing?

Thanks.
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  #8  
Old February 14th, 2008, 04:53 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Steve Febbraro View Post
So glad I found this forum, and the information on the micro-adust LCD chart and procedure.

I do have question however..When watching the direction of adjustment, looking down at the lens, does a leftward move mean the lens is backfocusing?
Hi Steve, welcome to OPF.

When you first let the camera autofocus, and then find that you need to focus the lens further away (rotate the lens anti-clockwise as seen from behind the camera) to achieve maximum moiré it means that the camera was front-focusing.

To get a sense of how much you need to adjust, I've used 2 small strips from a post-it note when I didn't have any other barrel markings I could use, and it made things easier. Try and stick one on the rotating focus ring part and one on the fixed part of the barrel, the pieces of paper just touching each other. After you use the AF Microadjustment tool to get perfect focus, draw a thin matching line on both pieces of paper. When you now use AF you'll see how far the rotation is off. Now iteratively change the adjustment setting until AF produces matching lines again. That works quite fast and all you are left with is some tests to see if the AF is consistent, independent of the focus approach direction (starting from closeup or infinity), and at other distances.

Bart
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  #9  
Old February 14th, 2008, 06:03 PM
Steve Febbraro Steve Febbraro is offline
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Quote:
Originally Posted by Bart_van_der_Wolf View Post
Hi Steve, welcome to OPF.

When you first let the camera autofocus, and then find that you need to focus the lens further away (rotate the lens anti-clockwise as seen from behind the camera) to achieve maximum moiré it means that the camera was front-focusing.

To get a sense of how much you need to adjust, I've used 2 small strips from a post-it note when I didn't have any other barrel markings I could use, and it made things easier. Try and stick one on the rotating focus ring part and one on the fixed part of the barrel, the pieces of paper just touching each other. After you use the AF Microadjustment tool to get perfect focus, draw a thin matching line on both pieces of paper. When you now use AF you'll see how far the rotation is off. Now iteratively change the adjustment setting until AF produces matching lines again. That works quite fast and all you are left with is some tests to see if the AF is consistent, independent of the focus approach direction (starting from closeup or infinity), and at other distances.

Bart
Excellent.

Thank you Bart for the explanation and for the welcome. I will apply your instructions to the process.
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  #10  
Old July 12th, 2008, 05:47 AM
Ralph Honsbeek Ralph Honsbeek is offline
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Default first attempt

Hi there ,

After one using the 1d Mark 3 for less than a month , I have found it quite hard to get the setup right. On my 40 D everything was perfect, just had to add a lens and shoot no problems. Now nothing but problems.

I have my 24-105 almost to my liking I think at -2 micro adjustment. But even now I am not
happy with it 100%

However I find calibrating my 200mm 2.8F L USM is a bit more challenging.
After using the Moire and a few distance setups 0 micro adjust seemed right to me and
I left it like that. I went out for a shoot and the problems are as followed.
When I subject cheek is aimed the eyes get in focus. The difference is very small but still
noticeable. If the AF point is selected and the images gets focus a little behind it , how should I go about adjusting the Micro Adjustments , plus or minus ?

Also , when calibrating the micro adjust as suggested in this forum my Mr. Van der Wolf ,
When using LiveView and MF to obtain perfect Moire , then going back to AF and looking ate the BARREL indicators, I wonder what it means if when barrel moves Left or Right,
If it moves to the right (More distance) will I have to add more - micro or more + micro > ?

Thank you for now

Ralph
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  #11  
Old July 13th, 2008, 10:15 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Ralph Honsbeek View Post
When I subject cheek is aimed the eyes get in focus. The difference is very small but still noticeable. If the AF point is selected and the images gets focus a little behind it , how should I go about adjusting the Micro Adjustments , plus or minus ?
The AF Microadjustment should be set to perfect focus on a flat plane. If I understand you correctly, then you see a focus difference between the cheeks and the eyes. That is a fact of life when viewing at the pixel level. Depth of Field (DOF) is very limited at f/2.8 and 200mm focal length. For instance, when you shoot at 2 metres distance, you'll have 5 millimetres (approx. 1/5th of an inch) total DOF beyond which you will see a noticable degradation of sharpness at the pixel level. At 3 metres focus distance, you stil have only some 12 millimetres (less than half an inch) of total DOF at the pixel level beyond which you see reduced sharpness. That's how critical the 1Ds Mark III will let you focus, and that's why the AF Microadjustment is so valuable. How much of that is visible in the output, depends on output size and viewing distance.

Quote:
Also , when calibrating the micro adjust as suggested in this forum my Mr. Van der Wolf ,
When using LiveView and MF to obtain perfect Moire , then going back to AF and looking ate the BARREL indicators, I wonder what it means if when barrel moves Left or Right,
If it moves to the right (More distance) will I have to add more - micro or more + micro > ?
While it sometimes seems hard to interpret, it is logical when you realise that the -/+ adjustment moves the actual AF focus plane forward/backward. So, when the AF focuses at a farther distance than it should, you need to adjust it it to a nearer distance, forewards. It could have helped if Canon had marked the scale nearer/farther (-/+).

Bart
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  #12  
Old July 13th, 2008, 05:29 PM
Ralph Honsbeek Ralph Honsbeek is offline
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[QUOTE=Depth of Field (DOF) is very limited at f/2.8 and 200mm focal length[/QUOTE]

I shot those with mu 24-105mm though
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  #13  
Old March 9th, 2009, 12:14 PM
Rod Witten Rod Witten is offline
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Remarkable tool !!!

Many thanks for your effort.

Rod Witten
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  #14  
Old March 9th, 2009, 12:36 PM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Rod Witten View Post
Remarkable tool !!!

Many thanks for your effort.
Hi Rod,

My pleasure. I needed it myself, because the other tools were not accurate enough, and I decided to share it with everybody. It is based on a solid physical phenomenon which we usually attempt to avoid. I decided to let it work for us, instead of against.

Bart
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  #15  
Old March 30th, 2009, 10:00 AM
Nicolas Claris Nicolas Claris is offline
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Default Caution !

Hi folks
Getting prepared for some upcoming important jobs, and founding that the latest shots with the 24-70 were not crystal sharp, I checked the focus using Bart's method and targets and found the settings not to be accurate anymore…
I then checked all my lenses (14 to 500…) made corrections after an overcheck with "natural shots' (not the target but something real).
I must say that the "real life" tests confirmed the accuracy of corrections made with Bart's target :-D

They all needed some adjustments and are all now ready for a new start.

I just wonder what could make the old settings becoming bad (used same method before, and got most of the shot tak sharp…).
Vibrations during transportation? (camera never felt down, nor the lenses).
Any idea?
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  #16  
Old March 30th, 2009, 11:21 AM
Asher Kelman Asher Kelman is online now
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Quote:
Originally Posted by Nicolas Claris View Post
I just wonder what could make the old settings becoming bad (used same method before, and got most of the shot tak sharp…).
Vibrations during transportation? (camera never felt down, nor the lenses).
Any idea?
Nicolas,

This shift is a big puzzle. Of course, you didn't upgrade the firmware in between then and now?

Asher
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  #17  
Old March 30th, 2009, 11:45 AM
Nicolas Claris Nicolas Claris is offline
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Quote:
Originally Posted by Asher Kelman View Post
Nicolas,

This shift is a big puzzle. Of course, you didn't upgrade the firmware in between then and now?

Asher
Hoops! damned, you nailed it!
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  #18  
Old December 20th, 2009, 06:42 PM
Isaac Burdeinick Isaac Burdeinick is offline
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Default Trying on Tamron 18-270mm

Hi Bart

Im going to try The Micro Adj. on the far end of Tamron 270mm @F6.3. For that need to do it at least at 13.5 Meters! that is a hassle... any suggestion? can it be done at less distance? I know that Canon tips say at 50 x the focal distance.
What would you do?
Keep it at -5 for the 18-50mm end? or change it to +3 for the Far end, Go back & forward...
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Old December 21st, 2009, 03:57 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Isaac Burdeinick View Post
Hi Bart

Im going to try The Micro Adj. on the far end of Tamron 270mm @F6.3. For that need to do it at least at 13.5 Meters! that is a hassle... any suggestion? can it be done at less distance? I know that Canon tips say at 50 x the focal distance.
Hi Isaac,

I'd do it at 270mm, and AFMA at something like 4 or 5 meters if possible indoors. The suggestions to shoot at 50x FL are old school. The number mentioned in the Canon tips by Chuck Westfall were based on shooting resolution targets on film (and maybe to calibrate a lens by itself). Film has a much more gradual and dithered fall-off towards limiting resolution. The absolute resolution of most DSLRs is lower than of fine grained film, and drops of fast once it approaches the limiting resolution (Nyquist). Also, when using my AFMA target moiré method, we exploit some properties of sampled imaging at 2 different sampling densities, so that's something different alltogether.

The only uncertainty with the Tamron is that at smaller apertures (e.g. f/6.7) there may be too little modulation to generate a useful moiré pattern. But since it's free, there is no harm in trying.

As always, I do suggest to check actual focus performance afterwards at longer distances (if you use the lens for such work) on a flat surface with some surrounding slanted areas to detect front/back focus. Always remember that the focus sensors are larger than the indicators in the viewfinder. When lenses use internal focusing, there could theoretically be different AFMA settings at different distances for a given focal lenght, so checking for that won't hurt and strengthens confidence.

Quote:
What would you do?
Keep it at -5 for the 18-50mm end? or change it to +3 for the Far end, Go back & forward...
I use the settings for the more critical longer focal length myself (because DOF increases towards short FLs anyway), but when there is a significant difference throughout the range, I'd either choose the most used FL, or select a compromise setting.

Cheers,
Bart
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  #20  
Old December 21st, 2009, 04:42 PM
Isaac Burdeinick Isaac Burdeinick is offline
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Thanks Bart:

Here are some Samples:

At Minus 5:
At Zero:
Plus 5:

I dont see much difference? they all are at 100%
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  #21  
Old December 22nd, 2009, 06:09 AM
Bart_van_der_Wolf Bart_van_der_Wolf is offline
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Quote:
Originally Posted by Isaac Burdeinick View Post
I dont see much difference? they all are at 100%
Hi Isaac,

First of all, did you use the recommended target I made available in post #1 for checking the focus on your camera LCD, or did you use this alternative one? With this alternative one, it looks like you need to increase the shooting distance to get some more moiré in the actual image, maybe that will help with picking a winner by looking at the actual image output. Maximizing the moiré, both on the camera LCD and in the final image, is the key to determining optimal focus.

Secondly, it is very likely that your widest f/6.3 aperture at 270mm focal length is generating enough DOF to not make much difference between -20 and +20 adjustment. Wider apertures have significantly more shallow DOF, making accurate focusing more critical and easier to check.

If you use the intended target, making sure you display it at 100% zoom (actual size, pixel per pixel) on your computer, do you get moiré at any focus position on the Live View camera LCD? If not, can you try different focus distance towards the target? The distance needs to be large enough to generate moiré in the actual image, but it may appear sooner on the camera LCD.

As a final resort you may try shorter focal lengths which allow a wider aperture, which should be okay if f/6.3 gives enough DOF to mask focus bias anyway.

Cheers,
Bart
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  #22  
Old December 22nd, 2009, 07:18 AM
Isaac Burdeinick Isaac Burdeinick is offline
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Thank You Bart

I Will go on and do it with the suggested target and more far away.
Ill post them after...

Thanks!
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  #23  
Old March 14th, 2015, 10:45 AM
Nicolas Claris Nicolas Claris is offline
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Hi Bart and all
This tool is still working great!
Over the past three years I couldn't use it because the Pentax 645D had no live view…
This is why I used the Micheal Tapes tool (see my post here).
For some peace of mind, i got used to verify quite oftenly (before every important shoot, those which cannot be redone) the AFMA with 'natural' targets (pedestrian cross road stripes, trees etc.) while on the fields…
So today was the day to adjust all my lens to the brand new 645Z, and forgetting Bart's tool, i adjusted all my lens:
25 mm - 8
55 mm - 6
80/160 - 2
90 mm - 3
120 mm - 5
300 mm = - 7
And suddenly, poking my head, I remembered that I could use the 645Z' live view and Bart's target
Bang! all settings confirmed!
When AFMA is good, one can see the small circles and some purple area around.

Nice : )

Thanks again Bart!
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  #24  
Old March 14th, 2015, 12:27 PM
Asher Kelman Asher Kelman is online now
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Bravo on getting the 645Z and also on being smart, optimizing this gem of a camera.

Did those first adjustments come from natural targets or using Michael Tapes tools? BTW, which version do you have?

This is an exciting upgrade!

Except for not having a fast flash synch speed, you're pretty well set. I find no practical limitation in only having low shutter speed synch on the A7R, as I hardly every use flash to overwhelm daylight and so darken the background and sky.

Asher
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  #25  
Old March 14th, 2015, 01:41 PM
Nicolas Claris Nicolas Claris is offline
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Hi Asher
The first adjustments came from natural targets, Michael Tapes does not recognize yet the 645Z files.
Flash sync is 1/125 fairly enough for me when I use it (mainly for some macros).

Yes this body is a great upgrade!
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  #26  
Old March 27th, 2016, 12:16 PM
Asher Kelman Asher Kelman is online now
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Quote:
Originally Posted by Nicolas Claris View Post
Hi Asher
The first adjustments came from natural targets, Michael Tapes does not recognize yet the 645Z files.
Flash sync is 1/125 fairly enough for me when I use it (mainly for some macros).

Yes this body is a great upgrade!
Nicolas,

I would hope that Michael updates his software. Have you let him know your needs?

Asher
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