f-number equivalent between m43 and FF

Started Mar 25, 2014 | Discussions thread
HumanTarget Senior Member • Posts: 1,379
Re: f-number equivalent between m43 and FF

D Cox wrote:

The final SNR depends (assuming technology of the same generation) on the amount of light falling on each pixel. This determines the uncertainty of the measurement of light by that individual photodetector. The more photons, the more certain the measurement.

Actually, shot noise increases with the number of photons, so the more photons the more noise, even though the SNR is increased.  And a lot of cameras have reduced read noise at higher ISO settings, in which case they get better measurements with lower light levels (though at a reduced SNR ratio).

The signal in a photographic image is the differences between pixels. The uncertainty (error bars) for each pixel gives a random, or noise, component when comparing the pixels.

Your definition of signal would suggest that a noisy image has a stronger signal (more difference between pixels).

The total area of the sensor is irrelevant. If you put the same lens on various sizes of sensor, the noise level in the part of the image that they all record will be identical. (Assuming they are the same generation of technology.)

But why would you crop the image of the larger sensor? I know of nobody who always crops their images to a lowest common denominator. That totally defeats the purpose of a larger sensor. More information gives you a better image.

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