D800 & Nikon 24-70: Your Opinion On This Photo

Started Oct 15, 2012 | Discussions thread
Fred Briggs
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DOF does not really exist - it is just a perceptual convenience!
In reply to Bright Angel, Oct 15, 2012

DOF is a tenuous concept at best, and all bets are off when you zoom in to a 100% view.   Basically only an infinitely thin plane is actually in focus in any photograph, with focus deteriorating in front and behind this point at a rate determined by settings such as aperture, focal length, and focus distance.

The issue with the concept of DOF is that it assumes a certain size of reproduction, viewed from a certain distance with a certain visual acuity.  Given all those assumptions, and knowing the camera settings it is then possible to say that a certain depth of field extending from some way in front of the focus distance to some way behind it will "APPEAR" to be in focus.

That is not to say that everything within this DOF is "ACTUALLY" in focus - it isn't, it is just that the specifics of the size of reproduction and viewing distance mean that it is not possible to discern the degree of out of focusness (if that is a word).

Viewing at 100% means that you have broken the rules governing what parts of the picture you can expect to appear sharp (even if they actually aren't) and viewing a D800 file at 100% is an awful lot of magnification!

If you don't believe me, look up a definintion of DOF and then try your own experiment.  Take a picture of a wall at an angle of approx 45% then look at the picture at different magnifications.  The amount of the wall which appears in focus will reduce each time you increase the magnification.  If you had enough resolution you could do this indefinitely and the apparent DOF would become infinitely small.

Fred

 Fred Briggs's gear list:Fred Briggs's gear list
Sony Alpha 7 Sony E 10-18mm F4 OSS Sony E 16-50mm F3.5-5.6 PZ OSS Sony FE 24-70mm F4 OSS
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