Calibrating at Both Ends of a Zoom Lens

This is just a quick post to show early development of a new feature in FoCal – the ability to test at both ends of a zoom lens and have the results interpreted for the best single result (or best dual results for cameras capable of accepting these):

Reikan FoCal Manual Mode - Calibrating at Both Ends of a Zoom Lens

FoCal 1.9 is mainly focused on stability and reliability improvements, but in doing this work we’re also taking a little time to add some features that have been on the todo list for some time.  The screenshot above shows the Manual Mode – which has been completely reworked “under the hood” to improve reliability and consistency of operation across Windows and Mac OS X.

In the image above, you’ll notice two prediction curves on the chart – one is for 17mm (the green line), and the other is for 40mm (the blue line), covering both ends of the Canon 17-40mm lens.  The predicted AF Microadjustment value is -2 at 40mm and -6 at 17mm, meaning for a camera with only one setting available, we should probably enter a value of -3 for best results (see this FAQ point for details).

This feature is still very much under development, but we’re hoping to have it enabled in FoCal 1.9, at least for Manual Mode and hopefully for the Fully Automatic/TurboCal tests too.

Interested in FoCal?

You can find information about the tests FoCal offers and how to purchase the software on the Version Comparison page.  If you want to get in touch, you can use our Feedback page.

One comment on “Calibrating at Both Ends of a Zoom Lens

  • James Martin says:

    That will be a cool feature. For a wide lens like the one in the above example, would it be practical and beneficial to calculate the DOF for the lens and use that to sway the value? I would think that at 17mm on a FF camera, the DOF would be great enough to absorb some of the adjustment where at 40mm it should be closer to the needed value as the DOF would be less.


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