75 lux on M8 vs. Film

[carstenw]

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Adams doesn't present the formula, but the relationships he states are equivalent to the formula I posted. If you look at it carefully, each of the relationships he states is implied by the formula.

 

Howard, K is the "fudge factor" It is everything else which wasn't mentioned in the formula, but which is needed to get the correct numerical answer. Since the right-hand side is unitless, and the left hand side has distance units, the factor must include distance units, and in fact this is probably the circle of confusion. If you make the circle of confusion smaller, then the left-hand values will be smaller too, given the need for sharper results that a smaller circle of confusion implies. In the "fudge factor" will also be unit conversions, since the numerical values on the right hand side give a different result depending on whether, for example, you use meters or feet.

 

Anyway, apart from the circle of confusion, the rest of the fudge factor is not interesting to photographers, except those who want to derive the true formula with all factors included.