Oly 45 f1.8 and Canon 85 f1.8 same DOF?

Started Jun 20, 2012 | Discussions thread
Great Bustard
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Re: You are exactly right
In reply to forpetessake, Jun 21, 2012

forpetessake wrote:

P.S. there is one mitigating factor, namely a smaller sensor produces less photon noise - proportional to sqrt(area), so discarding other factors the theoretical SNR for m4/3 is just 1 stop worse than FF.

I'm afraid I don't understand this point. The photon noise is a direct result of the total amount of light falling on the sensor and the proportion of that light that is recorded (the QE -- Quantum Efficiency -- of the sensor) -- the sensor size has nothing to do with it except inasmuch as lenses for larger sensor systems usually have larger aperture (entrance pupil) diameters for any given AOV.

But, yes, for the same exposure and QE, the FF sensor will have half (one stop less) the photon noise as an mFT sensor, since four times as much light will fall on the sensor during the exposure.

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