Along with the Canon / Sigma combination, I also have the Sigma USB dock that, among a few other things, allows you to write micro-adjustment information directly to the lens. For the 150-600, there are 16 adjustments for the different focal lengths and distances. This means the camera/lens/dock will need to be connected/disconnected/tested a minimum of 16 times... likely a bunch more. This seems pretty cumbersome.

Is it possible for me to temporarily forget I have the USB dock, and perform the micro-adjustment using the built-in features of the camera. Once done, make a note of the adjustment settings, transfer them to the lens using the dock, clear lens info from the camera, and then spot-check a few settings. This certainly seems easier to me, but it also feels like I'm overlooking something important.


1 Answer 1


It might be possible to do something like what you describe. Your biggest issue will likely be a lack of exact correspondence between units with the two systems. A +8 (or -12) adjustment with the camera won't necessarily be the same amount of change as a +8 (or -12) adjustment with the lens dock.

Doing lens micro-adjustment, even with just the AFMA capabilities of the camera, can be a tedious process. When you multiply the two focal length adjustments (at a single distance each) possible with zoom lenses in certain cameras with the four focal length adjustments at four focus distances each available with the USB dock you're adding a lot of complexity no matter how you do it. At some point the ability to micro-adjust probably starts to exceed the shot-to-shot consistency of the camera/lens combination.

My advice would be to do a test shoot with the camera and lens unadjusted before you begin the adjustment procedure. Shoot at the focal lengths and distances you anticipate you'll use the lens at the most. Take plenty of shots at each focal length/distance combination. Then review your shots to identify any particular problem areas. Select targets that are not ambiguous as to what area of highest contrast the AF system is locking onto. Remember that areas of sensitivity often are far larger than the tiny squares you see in the viewfinder and the camera will use the area of highest contrast in any AF area that is active. If you do this first you'll know where to concentrate when you do your adjustment procedure.

Dial in the focal length/distance combination that is in most need of correction using the camera's AFMA adjustment and then again using the Lens Dock (with the camera returned to "zero"). Compare the numbers needed to accomplish the same adjustment. Then do the same thing for the second most-needed correction and compare the two adjustment numbers from each method. Do the differences between the two sets of numbers share a similar ratio (i.e. camera is +10, lens dock is +8 for one adjustment and camera is +5, lens dock is +4 for another)? Do they share a similar offset (i.e. Camera is +10, lens dock is +7 for one adjustment and camera is +5, lens dock is +2 for another)?

If you can establish a pattern then you can proceed to use camera based AFMA at various focal lengths and distances (recording the settings for each combination). You can then clear the camera based AFMA adjustment and use the lens dock to apply the "translated" settings to the lens. Of course you'll then need to test to be sure it all worked.

In practice, even just using the camera based AFMA, with long lenses the adjustment session is usually only a starting point. Test charts aren't really large enough and test distances aren't usually long enough indoors to duplicate the way we use longer lenses in the field. So you'll always have a bit of adjusting on the fly to do to get the lens dialed in when you're shooting at very long distances. If you can establish a connection between the camera based numbers you find you need to apply in real usage settings and the lens based numbers then you can eventually refine the process until you have the lens dialed in for how you actually use it the most.


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