DotTune: AF tune technique without taking photos

Started Jan 31, 2013 | Discussions thread
Horshack
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Re: Has anyone tried this with an AF-S 50 1.8G?
In reply to inasir1971, Feb 1, 2013

inasir1971 wrote:

The optimal setting determined previously for my 50 1.8G on my D800 is -8 (for Av=f/1.8).

Using this technique the confirmation dot remains on from -20 through to around +2/+3. While that is consistent with the value that is known to be correct the confirmation dot is on for greater than half of the AF tuning range.

Anyone else notice very large ranges with some lenses?

I don't have my 50 1.8G with me to try unfortunately. A few points though. Are you waiting several seconds while half-pressing the shutter to make sure the green dot stays solid? I find that as I approach the two ends of the AF tune range (starting from -20 or +20 and moving inward), the dot stays on progressively longer before it flickers between a dot and arrow. I've also found that at those same margins the dot may sometimes stay on for 5 seconds but if I let the meter/rangefinder go to sleep (by releasing the shutter and waiting for the VF indicators to turn off) and then wake it back up I'll then get a flicker within that same 5 second period. I plan to perform some experiments to discern how the PD sensing might change between the first 5-second interval and after a sleep/wakeup cycle - you would think it was just be continuously evaluating the split-beam but perhaps the sleep/wakeup resets something in the PDAF module.

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