Originally posted by pschlute Disagree here. I accept it is a visual eyeball thing, but in your original post you claimed that DOF was 1/3- 2/3. It is not when using a distance that most folk will to calibrate their lenses. It may not be exactly 50/50 but is is a lot closer to that than 1/3 2/3 ! A simple visit to a DOF calculator will demonstrate.
Yes, you are right, 53/57 is close to 50/50. I ran 60 test shots with my DFA28-105, with sharpness quantified for each image, for the mean value I obtained a kind of bell curve with two shoulders beside the default manufacturer settings. So the maximum sharpness is not obtained with the default setting,
BUT the default factory does give the least deviation of sharpness regardless of initial lens AF conditions (pre-focus far or near), which is now totally understandable for me.
So, it's a personal choice:
- Do I want to use the default factory setting and have 99% of my images in good but not best focus?
- Or do I want to tweak my AF so that to have 50% of my images with maximum sharpness at one focal length at one focus distance and the rest of my photos less sharp then with default factory settings?
Personally, I prefer to have a little less sharp images, but that all of them are acceptably sharp. If I took a photograph for a very high value project for which I want to have the maximum sharpness, I'd focus in live view and use electronic shutter.
---------- Post added 01-10-19 at 07:57 ----------
Originally posted by UncleVanya The 1/3 front 2/3 back is more of a hyperfocal technique than a dof truth I thought.
It is funny how DoF can be manipulated to serve an own opinion. For when deciding where to focus in a frame , the 1/3rd 2/3rd DoF rule applies, but for AF tuning we should use 50/50 at close distance?
We have a little problem here... aren't we supposed to tune AF for best results in actual shooting conditions? Or we tweak AF at 4 feet distance that we will almost never use when taking photographs outdoors?
How much of the AF calibration performed at 4 feet (~1 meter) will still work when shooting subjects between 20 and 40 feet (~5 to 10 meters)?