7D Micro-Focus Adjustment

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Frank
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#1
Just finished doing the Micro Focus Adjust on my 300 f2.8 and I thought people may be interested in seeing the result. I shot a test chart at about 8 metres (only about 25x FL). Didn't bother with any slanted stuff, didn't bother trying to get the chart within 0.1º of parallel just eyeballed it (DoF is enough to make the whole thing a moot point). Shot at -20, -15, -10, -5, 0, 5, 10, 15 and 20 then compared the images, zoomed to 100%, in lightroom.

The screencap below shows the 0 image on the left and the +10 image on the right. Quite a difference. I also did the MFA with the 1.4x and 2x TCs - both came out at +5

 

dod

Droopy
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Ebenezer McScrooge III
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#2
Hmm, I've never really paid that much attention to the micro adjust, maybe I should.
 
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Robert
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#5
Am I right in guessing you should only use this feature on prime lenses?
not at all but they recomend you set the zoom at the long end for the ajustment.
Rob.
 
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#9
Very good. Just done the 24 - 105 and the 100 - 400 with and without the X1.4.

All needed a tweak, and supprised the difference it makes.

Cheers
 
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Andy
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#10
Nicely done. I use the same technique on my 1D. My 300 2.8 is at +8. You do need to check it "in action" though as I started with +12 from the same test but found that the lens was focusing a bit behind a running rugby player so brought it to +8 to fine tune it.

I agree though - it's a super feature.
 

Mr THX

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Chris
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#11
That's one for anyone with 'micro adjust' to sit up and read............:rules:
 
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hollis_f
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#13
Can someone explain for the thickos in the class how to do this?
Print out the test chart and stick it some something reasonably firm. Set the chart up so that it fills the viewfinder of the camera with your chosen lens. Try to ensure that the target is roughly parallel with the back of the camera.

Set your lens to its widest aperture, put the camera on a tripod and aim it at the target.

Format the memory card and use the menu system to navigate to

7D - C.Fn III -5 on page 211 of the manual
50D - C.Fn III -7 on page 180

Choose 'Adjust by lens' and press 'Set' (the button in the middle of the big dial) then press the 'Info' button. The lens you're trying to calibrate should have its name displayed. Use the big dial to change the value on the scale to -20, press 'Set' and half-press the shutter to exit menu mode. Manually change the focus so that the target is out of focus, half-press the shutter to focus then take a shot.

Press 'Menu', 'Set', 'Info' and change the setting to -15 then press 'Set'. Repeat the process for -10, -5, 0, 5, 10, 15 and 20.

You should not have 9 pictures. Upload them to your computer and check, at 100% zoom, which is the clearest.

You may find that there's not too much difference between three consecutive shots - in which case the middle of the three should be close enough. If there's a big difference then you may want to take more shots at intermediate vales. Suppose 0 is poor, +5 is good and +10 is poor. Then the ideal is somewhere between 0 and +10. Take more shots at +3 and +10 - compare them with the +5 and you should have a good idea which is the best setting.

Some people will go further and test every possible value. I've never found it makes that much difference if I choose +5, +6 or +7.

Once you've decided on a value don't forget to go back to the camera and 'Set' that value. The camera will remember it for that lens (or lens + TC combination). Then you can move on to the next lens.

I hope that's all right. I haven't stepped through it to check. But it should give you a good idea.
 
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hollis_f
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Frank
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#18
time for me to look a fool in front of you lot.

Can this be done on a 20D with a 100-400L?
Afraid not. It's available on the 50D, 7D, 5D MkII, 1D Mk III and 1Ds MkIII. AFAIK that's it. It was one of the reasons I got the 50D originally, after having experienced it woth my friend's 1D.

I've not had a lot of joy with it on zoom lenses - although I may give it a try with my new 70-200. But next in line is my new 100 Macro. For that I'm not sure if I should use the recommended distance of 5m from camera to target, or to try it at something like 1m - much more like the distances the lens is likely to be used.
 
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hollis_f
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Frank
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#21
While such a chart is good for seeing if you have got back, or front, focussing, it's not really very good for doing the Micro Focus Adjustment. That's because, despite all the guff written on that site, you can't be certain that the AF system is locking onto the black bar across the middle.

This is why a large target, parallel to the focus plane is best. If you really, really feel that you need the angled ruler as well then either spend $180 on a Lensalign Pro or spent a lot less on this alternative.
 
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Richard
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#24
As Hollis says, that's not a good focus test at all. Any test target shot at close distance is prone to inaccuracy and because they are hyper critical, also user error. Canon recommends a minimum of 50x focal length. This test and others similar will lead you to believe you've got a focus problem when in fact it's fine.

All lenses have tolerance, zooms are more prone at different focal lengths. If you are shooting unrealistically close and you set it to be spot on for that distance, there's a real danger that it will be out at more normal range.
 
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