AF micro-adjust

So, I decided to have a look and try to micro-adjust my lenses on the 50D. To start, anyway. Well, to say that I went into it half-assed wouldn't even begin to describe it! I don't really like Canon's idea of doing it because it is difficult to do unless you put up a sheet of newspaper print (which I might do tomorrow, outside in the sunlight).

This is Canon's suggested technique:

- Mount the camera on a good tripod.
- Set up a target for the camera to focus on. The reference target should have sufficient contrast for the AF system to detect. It should be flat and parallel to the camera's focal plane, and centred.
- Lighting should be bright / even.
- Camera-to-subject distance should be no less than 50 times the focal length of the lens. For a 50mm lens, that would be at least 2.5 meters.
- Set the lens for AF and the camera for One-Shot AF, and manually select the centre focusing point.
- Shoot at the maximum aperture of the lens via manual mode or aperture-priority. Adjust exposure level to get an accurate exposure. Use low ISO setting.
- If the lens has an image stabilizer, turn it off.
- Use a remote switch or the camera's self-timer to fire the shutter. Use mirror lock up as well.
- Take three sets of images at microadjustment settings of -5, 0 and +5, i.e, three consecutive images at -5, three consecutive images at 0, and three consecutive images at +5.
- Look at the images on your screen at 100% magnification.
- Take additional sets of test images at different microadjustment settings if necessary until the sharpest image is achieved.
- Register the corresponding microadjustment settings in the camera.

Long story short, I didn't really see much difference with the 24-70L, and my 85L looked a *little* better at -5 (I didn't try anything in between yet, I worked in increments of 5), but we're splitting hairs here! Either I am extremely lucky, or I was doing something wrong (then again, I never subscribed to all the whining about misfocusing Canon bodies, I am sure there are exceptions, but you know what I mean). I am going to do a little reading up on the matter, and have another (serious) attempt tomorrow, in full daylight (ran out of daylight today, told you it was a half-assed effort (even though I used my whole ass

Did you do a search here for this? Many threads already from people talking about their individual adjustment stories.

I went into a very well staffed, legendary camera shop yesterday to rent a lens and while there I asked about the micro-adjust feature and they all looked at me like I was crazy. They asked if I noticed anything wrong with my pics and I said no. However, I told them that I was advised to micro-adjust my lenses by several people and they said, "if it ain't broken, don't fix it." They suggested that if you have a problem with your picture quality that it might be an issue with a particular lens on a particular body and sending it into Canon for them to tweak it is a better idea. I have had no problems so far and my pictures are beautiful.

I left there feeling a little better about not micro-adjusting my lenses. If I start to notice any degradation of my shots then I will proceed with the very intimidating process of micro-adjusting.

my micro adjusting started with bits of paper at 45 degrees and ended in shooting a cereal box from across the room....

i ended up with about 5-8 on the 24-70, 11 out on the 100-400 as my worst 2... the others werent far off...

dont be intimidated - i just reviewed in camera the sharpness at full zoom on preview and kept clicking up and down until i was happy....

its so easy to just hit RESET all to "0" and your back to where you started...

dont be intimidated.. but like you said - if YOU cant notice - then there isnt anything wrong... me on the otherhand have NEVER been happy with the 100-400 nor the 24-70 and it was only until i got my hands on a 5d2 have i realised WHY these lenses look shiiiitty on my 40d...

I mainly want to dial-in my 85L and the rest of the primes (but the 85L in particular, to make sure I'm getting best out of it, even though I will not use it on the 50D most of the time). And it will be good practice for the future, when my other bodies get replaced.

For now, the 5D and 1D2N handle the 85L just fine...

I have a question. When you micro adjust on the 50D, does it remember the setting for each of your lenses? Does it have a memory so to speak that remembers that your lens #1 is +4, lens #2 is -2, lens #3 is +10? Or do you have to dial the numbers in manually every time you switch lenses?

gabebalazs wrote in post #7756725
I have a question. When you micro adjust on the 50D, does it remember the setting for each of your lenses? Does it have a memory so to speak that remembers that your lens #1 is +4, lens #2 is -2, lens #3 is +10? Or do you have to dial the numbers in manually every time you switch lenses?

Yup.......it can remember up to 20 individual lenses.

Oh to have 20 lenses !!!!!.....LOL.

Matt

Microadjustment is not as easy as some may think. One problem is understand how DOF affects the way you see an image as a sharp one.
Here are four examples of the effect of DOF and MA on the image. All of the images were taken with the 50d and the EF-85 f1.8 wide open. The level that serves as a target was placed at an angle of 45 degrees with respect to the camera. In that way you can check where the DOF moves when you change the microadjustment. The first image has a MA of 0, the second has +3 the third +5 and the last +7. The distance between the camera end the target line was of about 8 feet. Note how close the images are between themselves. Let us comment about how to interpret the results.

a) As we can observe in the images, when the MA is 0, the range where the image is focused goes from 7 to 9 (in the inches scale, where the focus was 8 inches, that is the vertical black line), in the centimeter scale we could say it goes from 17 to 24.
b) With a MA of +3 it looks about the same (probably the range has moved a little bit to the left). Using the cm scale we can say it goes from 16 to 23 cm.
c) With a MA of +5 it changes a little more, I would say from 15 to 22 cm.
d) With a MA of +7 it goes from 12 to 21.

Note how in all images the target line looks sharp (the last one is a little bit blurred but almost nothing). Remember that all these are 100% crops of the total image.

So, what are my conclusions about this testing of my EF-85 f1.8?. I would say that a MA between 0 and +3 appears to work fine, in the sense that the DOF will remain about half and half around the focus target.

It is also worth to advise that you have to take several samples at each MA level, since there are small variations of the AF at any given MA level (for instance, I took two samples at +5, one is the one shown here, the other was clearly worst than the +7 level.

Miguel

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Just a short 100% crop example of my EF-70-200 f4L IS. Shot taken at f4, 200mm. This monster is tack sharp where it should be. What a fantastic lens!!

Miguel

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On some lenses, such as 85L, I tend to dial in +1 from the absolutely correct setting (make it a nat's fraction front focusing) as I tend to focus on peoples eyes and this way I get to have the nose and eyebrows sharp too. Well it works for me

That's awesome. Thanks Matt.

This sounds like such a PITA. I think it would drive me nuts always analyzing every shot to make sure my last microadjustment really did make it better.

paparios wrote in post #7757581
Here are four examples of the effect of DOF and MA on the image. All of the images were taken with the 50d and the EF-85 f1.8 wide open. The level that serves as a target was placed at an angle of 45 degrees with respect to the camera.

Which is why the recommended method says -

Rudi wrote in post #7754946
The reference target should have sufficient contrast for the AF system to detect. It should be flat and parallel to the camera's focal plane.

If you use a target that is at 45 degrees then all sorts of extra factors can affect your MFA. In particular you can't be sure just which part of the target the AF mechanism is locking onto. Remember, the AF zone is substantially larger than the little red square.

If your target is parallel to the camera then the AF is guaranteed to choose something at the correct distance. That's why something like a book cover (what I used), a sheet of newspaper, a printed focus test chart or a cereal box is ideal.

Rudi - I was never seriously happy with my 24-70L until I did this. If you like to shoot wide open then it is definitely worthwhile to MA your lenses. My keeper rate was p*ss poor with my 24-70L until i did it.

I found Canon's (Chuck Westfall) method as you have listed definitely the best way to do it... the other ways (such as 45 degree focus charts and LCD moire patterns) for me were much too subjective. Once you get the methodology down-pat its very easy, fast and foolproof to do.

Here are some additional tips:
- shoot tethered and use the canon eos utility to take each picture instead of the self timer
- test at the longest focal length if a zoom lens. I also repeated the process for the most common zoom setting I shoot at with the particular lens to be doubly sure (eg. 50mm on the 24-70)
- before each shot turn the focus ring to infinity before you auto-focus
- open the images aligned as layers in photoshop file and zoom to 100%... simply switching the layers on and off makes it easy to judge the sharpest one
- take 3 shots at +/- 10, 15 and 20 also if you are not seeing the immediate difference between -5, 0 and +5
- once you find the two sharpest increments eg. +10 and +15 then take the shots in between (eg. 11, 12, 13, 14) and compare again to get your final adjustment amount
- I used something with lots of contrast as suggested for the reference target... my daughters Dora the Explorer canvas bag sat straight up, perpendicular to the lens was perfect! It had a colourful, contrasty picture on front and the canvas weave provided texture to easily allow sharpness to be judged.

Here are the results on my 24-70L (sorry no pics of Dora the Explorer ):

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hollis_f wrote in post #7759869
Which is why the recommended method says -


If you use a target that is at 45 degrees then all sorts of extra factors can affect your MFA. In particular you can't be sure just which part of the target the AF mechanism is locking onto. Remember, the AF zone is substantially larger than the little red square.

If your target is parallel to the camera then the AF is guaranteed to choose something at the correct distance. That's why something like a book cover (what I used), a sheet of newspaper, a printed focus test chart or a cereal box is ideal.

Well, I disagree. Note that the 50d AF system has no problem in locking in the vertical black strip (that is precisely what the extra 2.8 cross central sensor of the 50d does). What my examples show is that, besides the distance where the focus lock in, there is also the question of the DOF. For the example, where the camera was about 240cm from the vertical black strip, the DOF is of around 5.2 cm. Within that distance, the vertical black strip will be seen sharp (as is proven in at least three of the four examples). So a flat and parallel target (which I have also used), can be seen sharp but while the DOF can be clearly displaced from the normal infront 49/ behind 51% location (see http://www.dofmaster.c​om/dofjs.html for details). The effect of the MA is precisely to move or displace the DOF for the lens.

Miguel