Quote:
Originally Posted by chandrashekharbapat
Dear Sir,
I have gone through the article you have referred "Excerpt from Luminous landscape".
Still I am of the opinion that circle of confusion has nothing to do with the size of format upon which the picture is being recorded. It only concerns with the Focal length of the lens used. The writer is under some confusion. Arther Cox in his book Lens Optics has given a formula to calculate the size of circle of confusion as Focal length / 1000 in inches. Encyclopedia of photography also says the same thing.
The writer is mixing perspective with the size of circle of confusion.
chandrashekhar
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This is where your statement is wrong-we know for a fact that the circle of confusion for a 35mm format is 0.033333333mm...recurring,but if we use your division we get 1000/50=0.050mm-which is why diagonal of format/1500 is the more accurate.This whole system was originally developed in the 1930's, with the advent of 35mm precision cameras, as Leica and Contax,etc., The dof calculators and charts are only "near enough" indicators of dof and hyperfocal distance nowadays- they were designed for enlarging prints no more than 8 times magnification-maximum 11"x 14" held at arm's length-but when we look at our digital images at 100%(actual pixels) size is approx 40"x 50" so these calculators and charts are no longer 100% accurate.Ken.