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What is DOF?
Depth of field (DOF) is one of basic tools for every photographer. Books say that when you take a shot with specific aperture, not only the objects that are directly at the focus distance will be sharp, but all that fit within the depth of field. The bigger the aperture number (smaller aperture size) the bigger tolerance.In real life I encountered number of situations where focus was not good enough even at big apertures and this brought me to this test. My question is: is an object really sharp when it is within DOF, but not in perfect focus?
I am a physicist and could simply explain that it is impossible, and only those objects that are exactly at focus distance will be sharp, and that DOF is actually a range where blur is small enough to be tolerable, but I believe that visual comparison would be more welcome. It will show if the blur is indeed tolerable for you.
The test
I have takes several shots using my Konica Minolta Dynax 7D and Minolta 50mm f/1.4 at f/22. The distance was exactly 3 meters and focus was manually set to be perfect. All shots were taken from a tripod, without moving it or recomposing the image. All camera settings as well as RAW developer settings (RawTherapee 2.3, EAHD) were the same for every frame. Resulting images were upscaled 200% in ImageMagick using the simpliest interpolation.Default view shows a perfect focus shot. Hover the mouse over the text below to see how it looks if the focus was set within f/4, f/8, f/16 and f/22 DOF. Remember that lens aperture was f/22 therefore I did not leave the DOF. Differences between the images are because of different DOF, small tripod vibrations and because changing focus influences angle of view of the lens.
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