DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
OP Horshack Veteran Member • Posts: 6,168
Using global-default AF Tune as +/- 20 workaround

fpessolano wrote:

I tried and I got to a range of -14 and +20 ..... but since I reached +20, I actually cannot say what range I have. Or do I use +20?

Besides Marianne's excellent idea about defocusing the lens (post here), there is another way you can work around this. Marianne made a discovery last year that the body-default AF tune values have 2.5x the total amount of tuning range compared to the lens-specific values. The body-default is the configurable AF tune value that is applied by default to all lenses which don't have a lens-specific value configured. Both the body-default and lens-specific parameters use the same+/-20 AF tune range scale, but Marianne found that each increment of body-default value is coarser with larger impact on actual AF adjustment observed (post here). I haven't had time to confirm it myself but considering the source I'm sure it's accurate.

Here's what you can try. Delete the configured lens-specific AF tune value you have for the lens you want to tune. Then perform DotTune but use the body-default AF tune value as the parameter you change during the process, instead of the lens-specific parameter. This should presumably give you 2.5x greater tuning ability. Assuming your lens fits within the expanded +/-20 range of the body-default tune values, you'll have a workable solution of leaving your global-default set to that tuned value, although it means you'll need to change the body-default back to its previous value (which is 0 unless you've ever changed it before) if you use other lenses which don't have lens-specific values configured, otherwise those lenses will use your modified body-default value as well. When I have time I'll try to build a scale that converts between body-default AF tune values and lens-specific AF tune values, which should allow us to do a DotTune range using body-default values and then convert them to lens-specific tune values, at least when the midpoint fits within the lens-specific tune scale.

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