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.

Filed Under: Photography Tips

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