Technique for focusing "into your scene"

[lenicolas]

I guess forget all that noise....why "median of (A,B)" and not 1/3 towards the minimum extension or 1/3 of (A,B)?

You’re assuming the relationship between standard extension and focusing distance is linear, which it is not.
Just do the test : pick points A and B, mark the position of the standard and then put the standard on the median point. Are you now focusing exactly in the middle between A and B?


EDIT : actually you don’t even need a view camera to test this. If you have a lens with a focussing scale hanging around you can check the markings :



Here you can see that extension wise, 2m is halfway between 1.5m and 3m, when in your scene 2m is roughly 1/3rd of the way between 1.5 and 3m.