How Do I Measure Noise Using Photoshop? And What Is A Significant Change?

Started 2 months ago | Discussions thread
John Sheehy Forum Pro • Posts: 22,753
Re: How Do I Measure Noise Using Photoshop? And What Is A Significant Change?

FingerPainter wrote:

No. Shooting with the cap on results in no signal and no noise in light. It will give you information about camera-added noise, which is usually a small subset of the noise in a usable image.

It is not a small subset where it really matters.

If one concentrates on the brighter tones of lower and medium ISOs, then it may seem that read noise is insignificant, but then again, in those tones sensors of the same size do not vary much.

If one starts looking at darker tones and/or higher ISOs, or situations where you need white balance, and one or two color channels are a lot weaker than another, then read noise becomes the greater factor.

It is myth that read noise has become insignificant, and that we are hitting the walls of "physics" and necessary shot noise. Read noise can improve quite a bit, and color filters on sensors are extremely inefficient, and typicall losing over 80% of the light in an exposure. Getting rid of that loss would both greatly reduce photon noise by a certain number of stops in each color channel, but also reduce any given electronic read noise relative to exposure signal by twice as many stops, without even reducing the read noise as measured in electrons.

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