How does "total light" change SNR? II

Started Sep 14, 2014 | Discussions thread
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How does "total light" change SNR? II
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The last thread closed out with quite a few ignorant comments that I'd like to address:

Light is finite and fixed and is proportional to sensor area. Resampling has got nothing to do with the amount, it only affects resolution. You can resample a FF sensor as many times as you want but it will not change light. Subdividing the area does not change the total amount of light and yet equivalence is treating it as if it does. This is why it is completely bullcrap.

Actually, the bullcrap is saying that Equivalence says that sampling the signal with more pixels changes the total amount of light. In fact, Equivalence says the exact opposite -- that the total amount of light that makes up the photo is independent of the pixel count.

Futhermore, statements from the same poster in a previous post, such as:

This kind of argument shows lack of understanding of sampling theory. Same sensel density results in the same sampling frequency.

show that he got the two sentences exactly backwards. Specifically, the same pixel density on sensors with different sizes results in different sampling frequencies since the natural and implicit conditions for the comparison are the same perspective and framing.

The above poster's conclusion does not end there. He closes his post with:

The only conclusion and the only correct conclusion is that sensor size has absolutely got nothing to do with photographic exposure and therefore total light is meaningless when not associated with total sensor area. Photography has always been and always will be LIGHT SPREAD OVER AN AREA. Ultimately, noise is the same regardless of format.

which demonstrates a *gross* misunderstanding of both Equivalence and photography. First of all, no one says, or implies, that sensor size has anything to do with exposure except inasmuch as the same DOF and shutter speed will necessarily result in a lower exposure on the larger sensor.

Furthermore, photography has always been about the total amount of light that makes up the photo, not the amount of light per area.

Lastly, I would be hard pressed to find a self-harming post where anyone has said anything as stupid as "Ultimately, noise is the same regardless of format."  Even in the case of Equivalent photos, which results in the same total amount of light falling on the sensor, the noise also depends heavily on the sensor efficiency.

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