Micro Focus Adjustment

[Guest DaveW]

https://www.lensrentals.com/blog/2008/12/this-lens-is-soft-and-other-myths

This problem is mainly noticed with wide apertures where depth of field is not large enough to cover any focus inaccuracy and particularly with wide angle rather than telephoto lenses. Some professionals in the past used to send in all their cameras and lenses into the makers to be "harmonised" so they were all in focus on those combinations. OK until they bought a new camera. In those days focus harmonisation was really only possible by the camera makers or repairers, not the photographer themselves.

These days many new cameras have micro focus lens adjustment where you can adjust each lens for focus and the camera will remember that lens adjustment and automatically set the camera to it when you put the lens on:-

http://ophrysphotography.co.uk/pages/tutoriallensmicroadjustment.htm

Of course the photographer needs to know how to set up and use a test target to use the adjustment, or they will more likely put it out of focus rather than improve it.

http://www.the-digital-picture.com/Photography-Tips/AF-Microadjustment-Tips.aspx

An interesting quote from the Ophyrys link:-

"Expect some minor variations in focusing accuracy within each set of three test images, even though they were all taken at the same microadjustment setting. This is completely normal, and is due to the tolerances of the camera's AF system."

This is the very reason manual focusing using the human eye on the focusing screen is recommended for higher magnification macro work as at depths of field of a couple of millimetres or so as autofocus is too inaccurate.

DaveW

Edited January 9, 2013 by DaveW