Photo Maths
Exposure value
EV is a base-2 logarithmic scale defined by:
EV = log2 N2/t
where: N is the f-number
t is the exposure time ("shutter speed") in seconds
EV 0 corresponds to an exposure time of 1 s and an aperture of f/1.0
Focus Stacking
step size
2cn(m+1)/(m^2)
c = circle of confusion = 0.015 for m4/3
n = f number
m = magnification
eg.
2 * 0.015 * 8 * (1+1)/(1^2) = 0.3
Equivelant f stop
f = 1 / (Mg / (2 * Na))
Mg = magmification
Na = normal f stop
eg.
1 / (1 / (2 * 8)) = f16
@ 1:1 +2stops
Extension tubes
New magnification = lens mag +(extension/focal length)
1 + (26 / 60) = 1.433
Backlinks: Photography:Exposure
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