AF Micro adjustment Tutorial
Focusing systems in modern DSLRs have been long criticized for accuracy problems. Phenomenon seems to be persistent across different brands. No matter if you shoot Canon, Nikon, or something else, chances are you have encountered situation when camera lens combination focuses slightly ahead or behind intended target. This focus weirdness is known as: ‘front focusing / back focusing’ among photographers.
Major camera manufacturers have realized the need for cheap solution to front or back focus problems – probably annoyed by number of cameras returning to their factory for calibration, they have created an awesome Micro Adjustment feature. Don’t get too excited now, they didn’t do this to make our life easier – chasing higher profits, manufacturers shaped this feature to avoid repair labor and shipping costs.
Nevertheless Auto Focus Micro Adjustment is a blessing – it enables photographer to fine tune lens to the camera body for optimal focus accuracy.
Cameras with micro-adjustment currently include: Canon 1DIII, 1DIV, 1DsMkIII, 5DII, 50D, 7D, Nikon D3, D3x, D300, D700, Sony A900, Pentax K20.
Instructions
- 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 centered.
- 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 center 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 micro adjustment 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 micro adjustment settings if necessary until the sharpest image is achieved.
- Register the corresponding micro adjustment settings in the camera.
Notes
For best results, manually set the focus on the lens to infinity for every exposure before allowing the camera to autofocus the reference target.
Expect some minor variations in focusing accuracy within each set of three test images, even though they were all taken at the same micro adjustment setting. This is completely normal, and is due to the tolerances of the camera’s AF system.
Expect smaller micro adjustment settings to have a greater effect with telephoto lenses, and vice versa for wide-angle lenses.
If you are attempting to set micro adjustments for a zoom lens, it is important to realize that the camera’s setting may only be accurate for the focal length setting you test. The instruction book suggests testing at the longest focal length of the lens, but you may find it more efficient to choose the focal length you use most often.
*Keep in mind though; AF micro adjustment is just a part of the solution. There are many contributors to softness: photographer mistakes, damaged camera or dirty lens.
Feedback
SLR camera is a complicated tool and at times can be overwhelming for new users. There are so many things that can go wrong. If you read this article and still have questions, feel free to leave comment below – Include all possible details, and I will try to help you.
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There are 12 comments on this post.
Trackback URL | Comments RSS FeedRegarding AF micro adjustment,I don’t understand what should be flat and parallel to the camera’s focal plane,please explain it to me.Thanks.Jay
Hello Jay!
The talk is about your target for testing focus accuracy. For example you can use a book; it’s flat and it has contrast. You must place it parallel to the camera in the very middle (when you look through viewfinder you should see it centered).
Is it clear now? please let me know if you are having further problems…
Sandro.
I have a Canon Rebel XTi, and using SIGMA lens 18-250mm f/3.5-6.3 DC OS HSM.
I am having issues where lens keeps trying to focus in AF mode, and does not allow me to click.
I have to move lens to MF mode to click, is this because of Micro Focus Adjustment capabilities need to be reprogramed , not sure , please advise
Thanks
Puneet
Can we adjust two differdnt point like I have canon el 16_35 lens adjust on one on 16 mm and 2nd on 36 mm set on two diff. Points and when I need save on that point.
Abbas » nope, you need to choose 1 focal length and adjust it there. Check out your old photos, look at focal length carefully, understand where you shoot the most and adjust that one. Camera manufacturers recommend to use long end (35mm in your case), and it makes sense on wide end few mm of focus variation wont be even visible.
My gear is Canon EOS 450D, and I have EF 24-70 mm f/2.8 L USM. Before I write this thread, i’ve tested and i guess that my lense problem is backfocus. So, I want to ask that AF-MICROADJUSMENT feauture works in body camera or lense?
And if I adjust my lense with AF-MICROADJUSTMENT at my friends body camera, it is 5DMK2. Can it be fixed my lense backfocus problem when i using my Canon EOS 450D? Thanks
Andry » Hello,
Unfortunately Micro-adjustment is a camera-body feature. So, basically you tell camera that particular lens is front/back focusing, and body takes this into consideration while calculating focus when you half press the shutter button. You had a very good idea, but it will not work, because no information is written or update inside the lens chip.
Thank you for all the information. I have 3 questions. 1) Is there somewhere I could print out a standard “chart” so I could print out on a piece of paper to use it as the target for measuring? 2) As for zoom lens, can I measure for the longest and then shortest focal lengths and then find the middle micro adjustment setting, say if +5 adjustment is needed for longest focal length, and -1 adjustment for shortest, I could choose +3? 3)Have you heard the sharpness issues with Canon 5D Mark II despite all the calibrations/lens tests? I just bought one and even my old Nikon D70 show much sharper images! Of course the D70 can’t compete in low light and pixels and many other things but I just could not get sharp images with the new canon and I read that “small” percentages of owners have that issue. The thing is that the pictures don’t seem to even show any sharpness anywhere in a 3D image. For example I could focus on a subject’s eye and the picture would not show any sharpness on the nose, hair, skin, eyes, eyelashes, etc. Thanks
frankie » Hi,
1) You can print it on your home printer, in other words: it doesn’t matter.
2) No, you can set micro-adjustment only once. And canon recommends the longer end.
3) Very rare, 5D mkII is a good performer usually.
Which lens do you use?
Are you ware of Depth of Field? 5DmkII is full frame, thus fast lenses (such as f/1.8) will produce very think DOF. It’s easy to miss focus.
But without seeing a sample image it’s hard to tell. Send me a sample! (use contact form of the website).
does micro adjustment get affected if you mount a protective filter after doing the adjustments ?
Sandy » No, micro-adjustment will work just fine with or without filter. But bad quality filters can cause focus hunting, blur, and scattering of light.