Amazing lens, incredible sharpness

thk0 wrote:

Great Bustard wrote:

thk0 wrote:

Great Bustard wrote:

thk0 wrote:

I was questioning whether eg 4x more total light (ff at same f-stop) gives exactly 4x less noise.

4x as much (2 stops more) light will result in 1/2 as much (1 stop less) photon noise. The other player is read noise (the additional noise added by the sensor and supporting hardware).

Got it. Done my homework. SNR scales as sqrt intensity for shot noise.

The SNR is proportional to the sqrt of the total amount of light (as opposed to the intensity of the light) that falls on the sensor.

I knew you were going to say that as soon as I posted.

I omitted for a constant area. Yes, total light as you say.

Total Light vs Exposure is like mass vs weight.  That is, in the same acceleration field we can use the terms "mass" and "weight" more or less interchangeably (e.g. 78 kg vs 179 lbs on Earth), we can use exposure and total light more or less interchangeably for a given sensor size (e.g. f/2 1/100 puts 4x -- 2 stops more -- light on the sensor than f/4 1/100).

However, just as we need to make the distinction between mass and weight when the objects are in different acceleration fields (e.g. 79 kg on Earth weighs 179 lbs, but 79 kg on the Moon weighs 30 lbs), we need to make the distinction between total light and exposure when the sensors have different sizes (e.g. the same total light on a FF sensor has one fourth -- 2 stops lower -- exposure than on an mFT sensor).