Canon 50D AF Microadjustment - Instructions/Tutorial

Next chapter in our ongoing 50D review:
Auto Focus (AF) Microadjustment
(Also known as C.Fn.III-7 fun-o-rama!)

I'll fess up, one of the first things I did after getting my Canon 50D was to pop my EF 24-105 f4L IS in place, put the camera on a tripod, point the lens at the concentric circle AF Microadjustment target that seems to be making the rounds, and start trying to tweak my auto focus. I thought it would be quick and easy - and that I'd see great new sharpness from all of my shots... <chuckle>

Okay - so I didn't think it was going to be that easy, but I didn't have much luck in my first attempt.

The pattern I used, which I found by searching with good old Google, is posted later in this post. I found the first versions of it in this thread on openphotographyforums.com. I also found a page w/ a similar target (same pattern, different file size) on Northlight Images' website here; but the instructions seemed a touch incomplete to me.  (As an FYI - I do think the Northlight page - the one linked to the word "here" - is worth reading - it is much shorter than the series of posts, responses, questions, etc. in the thread.)

Allow me to 'splain - no - there is no time...
Allow me to sum up...

In short - you need to use a special target on an LCD based monitor (a printout will not work - it has to be shown on a LCD) - the test procedure counts on the interference between the LCD screen showing the pattern and the sensor to show as a pattern (called moiré - pronounced "mwah-ray") when the focus is sharp. Show the pattern at 100% on said monitor, set the camera for center AF point only, aim your camera square to the screen at the center of the pattern, turn on live view, get the most distinct interference pattern you can, turn off live view, and then watch the distance indicator window on your lens as you half press the shutter to have the AF focus on the screen. If the scale moves in the window, the AF Microadjustment is off... Make a tweak and then re-test. Oh - and be sure to do each lens individually, I'd be shocked (and would tell you to go out quick and buy a lottery ticket) if all your lenses came back the same correction...

Sounds pretty easy... but... I had just a few questions after reading the post I reference above:

1. How far away should the camera be from monitor showing the target?
2. What aperture should I shoot with?
3. So, if the distance scale does move, which way do I need to "adjust" the lens? + or - ?
4. Is the pattern test the best test?

The first attempts were admittedly rushed, and I had a hard time seeing any real difference, and I thought that zero adjustment was the best for the 3 or 4 lenses I tried... But I knew intuitively that couldn't be the case, so I stopped that test, and got on with some other playing with my new camera that day.

After doing some shooting, the dead pixel testing with its discoveries/fix (doh! - been meaning to post that one - perhaps Thursday), and the shooting of an event behind me, it was time to get back to the AF Microadjustment.

So today I got things setup; and, being just a touch less rushed, I was able to refine my process just a bit (okay - quite a bit), and was soon seeing some results.

After reading through the long series of posts from the OPF, I was clearer on a few things. 1 - keep your lens zoomed to its maximum zoom level; and 2 - be sure to keep your aperture cranked as open as possible (smallest number your lens will shoot). This does two things - it ensures the shallowest depth of field, and it ensures the shallowest depth of field... (no - that wasn't a typo, both actions minimize the DoF).

So having thought on this a bit since my first attempt, I figured that when the tiny pixels on my laptop's high res but not huge screen combined with the finer resolution of the sensor on the 50D, and with the finer resolution on the camera's screen, perhaps the moiré wasn't the best test for the 50D AF Microadjustment. I quickly  created my own test pattern with one pixel wide lines in a grid, with a few of the lines either wider or a different color so you could tell where you were in the grid when zoomed in on live view. My thought was that I should use laptop monitor at a 45 degree angle to the camera, and I could then use the tight DoF and the snazzy new screen to pixel peep to see which individual pixels on the laptop monitor were out of focus relative to where the center point focus pipper was placed. I guessed it would work better than the tutorials which had been created for the 1D Mark III and 1Ds Mark III with their lower resolution screens.

To save details - nope - didn't work so great for the short lenses, but did come in handy later... I found that the moiré works great for wide to medium lenses, and that my pattern worked better for longer lenses.

The Answers: (well - what worked for me at least)

Keep in mind that you should have the zoom at its maximum zoom - I had live view set to "Quick Mode" and never hit the "AF-On" button - I manually turned the focus ring. Oh yeah, and one shot AF with the center AF point selected.

1. How far away should the camera be from the monitor showing the target?
When testing wide to medium zoom (say, up to about 100 mm), I used the circular pattern and found that it helped to have the pattern come close to filling up the frame top to bottom. For my 24-105, it turned out to be about 50 inches from screen to where the sensor is in the camera (you know that little circle w/ the horizontal line through it that you see when looking down on the top of your camera? That horizontal line shows where the lens is focusing - the front of the sensor); for my 17-55 - about 30 inches; and something like 20 inches for the 10-22. When in live view, just ensure you see the interference pattern clearly - play around with the 5x and 10x live view if need be.

2.  What aperture should I shoot with?
Use the most wide open aperture (the smallest number) to minimize DoF.

3. So, if the distance scale does move, which way do I need to "adjust" the lens? + or - ?
I was a touch confused by the "Forward" and "Backward" labels on the adjustment screen. I then almost scratched a hole in my head trying to come up with a way to explain what they meant - I soon gave up and came up with how I got my head around it.

Seated behind the camera, I'd see the distinct pattern in live view; I'd turn off Live View then half press the shutter. If I saw (for example) the distance scale shift to the right as I looked down, that meant I had to turn the focus ring counter clockwise (or - ) to get the moire pattern back. If I saw the scale jump to the left, that meant I had to turn the focus ring clockwise (or + ) to get the pattern back. So I soon ignored the words on the adjustment menu, and just moved the pipper to the - or the + as needed.

4. Is the pattern test the best test?
Well - yes and no. I found that for my 10-22, 17-55, and 24-105 - the circular interference method worked the best; but when the longer lenses came out, my 70-200 (zoomed to 200 - remember - zoom to high end) and 100-400, I found that it took so little to shift the pattern, that I had difficulty getting a distinct pattern to be consistent. It might have been that I was testing in my kitchen and was running out of room to move the tripod away from the monitor, but I found using my target worked pretty darn well. Again - show the target at 100% view, but this time, turn the monitor on an angle so that it is about a 45 degree angle to the camera. Center the camera on the thick lines that cross in the center of the target. Now turn on live view, zoom to 10x and you should be able to manually focus so that the vertical line is sharp, with DoF fall-off to the left and right (assuming you pivoted the whole laptop on the counter/desk, if you tilted the monitor away - the horizontal line should be sharp w/ DoF fall-off above and below).  Now turn off Live View, half press the shutter to let the AF operate, and then turn Live View back on - zoom back to 10x... if the live view display has changed, you easily be able to see if the focus has shifted to a portion of the screen that is closer to you (if so, you would need to turn the focus ring clockwise, so add to the AF Adjustment) or if it is focused further away (you need to turn the focus ring counter-clockwise to get the center point back in focus, so subtract to the AF Adjustment).

A few pics w/ my target being used (click to enlarge):

From left to right:
My setup;
the pipper on the crosshairs of my target;
this 10x zoom shows what it would look like if you needed to subtract correction.
micro adjustment, micro adj, nikon, 1D mark III, 1D mk III, 1Ds mark III, 1Ds mk III, sigma, tamron, micro-adjustment

Okay - so that's it then? You betcha!
But wait - there's more!
NOW how much would you pay?

For those who are interested in a longer winded version of the test... here goes... I'll just try to bang this out as it is getting late and I do need to get some shut eye.

1. Be patient - take your time - don't rush this - or you will get *very* frustrated. The moiré pattern's changes as you barely nudge the focus ring can be VERY SUBTLE (in caps for irony's sake) - so don't do this after three espressos and a red bull.

2. Setup your camera on a very steady tripod. When you get to your longer lenses, you will notice any subtle movement is magnified greatly by the distance to the screen. (See step 1...) Ensure your camera is leveled.

3. Display your choice of target at 100% on a LCD display - I put my laptop on the kitchen counter.

4. Set the height of the center of your lens to be the same height as the center of the target you are using.

5. If you are using the moiré target, square up the camera to the screen - if you are using my target, angle the screen at about a 45 degree angle to the camera.

6. Set your Live View to quick mode, your aperture to wide open (lowest number), set AF to use only the center point, and set the distance between the camera and the target to the closer end of the focus range of the lens. As an example If your lens can focus at 1/2 meter, then move the camera to about 3/4 of a meter away from the target. The target should fill most of the height of the frame (you don't want it too big - unless you are using my target). Some lenses that have IS (image stabilization) will sense if the camera (or lens) is mounted in a tripod, but to be sure - I suggest you turn it off manually to be sure.

7. Focus on the target in Live View - If you are using the circular pattern target, get the most moiré pattern you can (see the example images on this page from Nortlight-images.co.uk), or if you are using my target - focus on the intersection of the thick black lines (3 px wide) at the center of the target.

8. Turn off Live View, watch the focus distance scale in the window on your lens to see if it moves while you 1/2 press the shutter to activate the camera's auto focus. remember which way the focus scale moved

9. If the focus distance scale didn't move - you are done! (If this happened the first try - you might try steps 7-9 a few times to ensure that your precision in step 7 was accurate) You can also verify by going back into Live View and seeing if you see the same amount of moiré you did before. Or if you are using my scale, see if the thick line is still in focus properly.

If the scale did move - proceed to step 10

10. hit the "menu" button, index wheel over to the Custom Functions menu (the second from the end) and choose "C.Fn III: Autofocus/Drive", then choose 7 - AF Microadjustment, and ensure it is set to 2 - Adjust by lens.

11. If this is the first time AF Microadjusting this lens on this camera, hitting the "info" button below the LCD will "register" the lens and take you to the AF-Microadjust screen; if you've had this lens on before and adjusted it, or if you are looping through, making changes and checking, hitting the "info" button will allow you to "change" the microadjustment in the AF-Microadjustment screen.

12. Now - make an adjustment to the correction value. If it moved a lot, try adjusting the value by 10, if it moved a little, try 5. + or - ?  Well - if you are using the circular rings target:  If the distance scale shifted to the right - adjust in the minus ( - ) direction... If the distance scale shifted to the left, adjust in the plus ( + ) direction.  My Target: if the focus shifted to a portion of the pattern that is closer to you, adjust in the plus ( + ) direction... if it is focused on part of the pattern further away, adjust in the minus ( - ) direction.

13. Be sure to hit the "Set" button (the button in the center of the thumb-dial) to save your change!

13. Now go back up to step 7 and repeat the process until you do not see the focus ring shift.
nikon, sigma, tamron, micro adjustment, micro adj, 1D mark III, 1D mk III, 1Ds mark III, 1Ds mk III, micro-adjustment

Okay - that pretty much wraps it up...

Just as an illustration, here are the adjustments that my lenses needed:

Lens:	Adj:
EF-S 10-22 f/3.5-4.5	-5
EF-S 17-55 f/2.8 IS	+7
EF 24-105 f/4L IS	-7
EF 70-200 f/2.8L IS	-4
EF 70-200 f/2.8L IS + 1.4x TC	+1
EF 70-200 f/2.8L IS + 2x TC	-3
EF 100-400 f/3.5-5.6 L IS	-4

Be sure to note that the camera does save separate micro adjustments when you are using TCs with your longer zooms. So there are three adjustments saved with the 70-200 f/2.8L IS, one by itself, one when using the 1.4x TC, and one when using the 2x TC. Pretty cool.

The Targets:

The moiré target from this thread at OPF:
 

My target - feel free to share early and often:

Okay - I'm going to have to crater now - good night and thanks for reading!
micro adjustment, 1D mark III, 1D mk III, 1Ds mark III, 1Ds mk III, nikon, sigma, tamron, micro adj, micro-adjustment

Comments

[Rob61]

Shouldn't this be "cranked as OPEN as possible"? You close the aperature (make smaller) when the numbers get larger. You open the aperature (make larger) when the numbers get smaller. There is an inverse relationship between the f stop and the aperature size.

[WillShootPhotos]

Yup - and corrected - the joys of writing at midnight - LOL. Thanks for the catch, I had it correct once or twice later in the post... I'll be re-reading the post after a cup of coffee this AM. - Will

[Chris]

Hi Will,

Thanks for the great post and I had a trial run doing a MA on my 24-105 & 70-200, however the one thing I'm not clear about is when you view the moire pattern on Live View, do you view it at normal maginification ? or at 100% ?(at 100% I can see the LCD grid and I manually focused to get that as sharp as possible) or should I use some other maginification ??

Cheers, Chris

[WillShootPhotos]

Chris,

Well - I think you may be confusing "LiveView" with "image review" as there is no 100% view for "LiveView".

If you are using the moire pattern test (remember - the screen should be square to the camera - vertically and horizontally), this will only really work while using "live view". I found that full image worked the best for seeing the moire for me, or the 5x view. the 10x view seemed to get the pixels too large to create the interference needed to get the moire pattern...

If you are shooting photos and doing a review of the image you just shot, or are using my target with live view. Remember to have the screen at a 45 degree angle to the camera. Then 10x in live view, or 100% magnification on playback worked best for me.

Hope this helps - let me know if I can answer anything else.

- Will

[Chris]

Will - thanks, I meant to indicate Live View at 10X, not 100% ... mea culpa

The other 'tips' are great also :-)

[Martin]

Thanks for the detailed post - I've now tested all my lenses ;-)

[Dave]

This may have been discussed previously, but why can't you just shoot at a subject with high detail, and check for correct focus by enlarging the image on the LCD screen?

[WillShootPhotos]

Dave - the main thought here was that the moiré test would make the process a bit faster than zooming in on an image after each shot. The other consideration (w.r.t. my target) is that it gives you (w/ the crisp pixels and other monitor elements) a consistent detailed target to better evaluate where the true focus point is. Sure - any detailed item will work, but if it is rounded, has an irregular shape, etc, quick evaluation of amount of fore/aft focus may not be as easy as with a manufactured target. Thanks for reading - hope this helps! - Will

[AC Adapter for CANON CA-570 MV700 MVX150i MVX25i]

Fantastic blog!

[Wedding Photographer France]

Brilliant - thanks for this explanation! I will be testing this tonight on my less than impressive 17-55 2.8 is and 50d!

Blaise

[Joe]

Did the adjustments make significant difference in image quality?

[WillShootPhotos]

Joe - not sure if you're asking me or if you're asking Blaise, but I did notice (as expected) sharper focus at the focus point... I had just subtle adjustments to make, but they did help.

I've since sold my 50D, and haven't had a chance to run the AF Microadjustment on my new slew of lenses and the 5D Mark II that I picked up. I had to ditch the EF-S lenses (since they won't work on either a FF camera like the 5D2, nor on the 1D Mark IIn that I have) and have picked up a 17-40 F/4L and a 15mm f/2.8 fisheye (which I prob won't micro-adjust for obvious reasons).

Thanks for reading and let me know how the adjustments work for you.

- Will

[Andrew]

Will,
I don't understand "get the most distinct interference pattern you can"
I have 50D and tamron 17-50 to test
Sorry for my poor english, but please explain in the very clear words...
Thank you..

[WillShootPhotos]

Andrew:

Try reading "the thread" link in the first paragraph - they may re-word it differently... The only way I can think to explain it is to say that the image alone is a set of circles or ripples. The "interference" shows up as putting smaller circles or other non circular patterns... Just try looking at the live view as you manually change the focus. You will see the pattern change from just circles to having other patterns showing up to the top/bottom and left/right of the center of the ripple image... the more of these patters are better, and mean you're in sharper more accurate focus.

Hope that helped! Thanks for reading!

- Will

[Andrew]

OK. Now I get it. Sorry for late reply.
Still have a question :
Can we do the AF micro adjustment on a 50mm f/1.8 II with erratic focusing issue? Sometimes its back focus, sometimes front focus.

[Lensmen]

Thanks for this detailed explaination. I will try these over the weekend with my 7D. Really upset that I am having low keeper rate

[WillShootPhotos]

Lensmen - I think another post on this blog may help a bit as well - http://blog.willshootphotography.com/2009/06/autofocus-performance-technique-and-technology.html - no camera is "perfect" and if you understand how different modes (and how which AF point you've selected) affect the AF performance, your keeper rate will go up!

Thanks for reading and feel free to use the "contact" link in the header to ask specific questions.

- Will