k1 pixel shift - can you see the different?

JeremieB wrote:

James O'Neill wrote:

JeremieB wrote:

Pixel shift of course may have an effect on details, but that depends a lot on overall sharpness of the scene (lens vs sensor etc).

But pixel shift has a definitive effect on reducing noise, as you take the mean of 4 captures instead of just 1.

I have never understood HOW this works. I've done tests to show that it DOES work.

If you have PS off, a pixel is might be Red, Green or Blue. The other colours are made up the average of the neighbours with that colour.

But you have PS on there is a single reading for Red and Blue and two for green each site. There should be less averaging with PS. (Unless each image is demozaiced and the 4 are averaged, but that would reduce resolution)

There's more light captured, so there should be less noise, but I can't get my head round the mechanism, unless it the extra data playing a role in NR.

Take 1 picture of size m x n, resize in half to get a picture of size m/2 x n/2 (remove high frequencies before resizing of course to avoid aliasing).

New picture will have better S/N ratio, it's sort of pixel binning in fact (half pixels with 4 times more "light" per pixel). That's the averaging I talk about. Averaging being a blur - there's less visible noise and better S/N. That's also exactly the same effect as when we capture a huge number of photos in astro, then stack them to reduce noise. Averaged same signal remains same signal, only the noise gets step by step lower / closer to the "true" signal (well, shot noise, noise that is not random is not concerned).

That's all good.

PS works the same except it starts from 4 images (that can be considered the same as 1 image of twice the size in each dimension, That's what others do with super resolution).

Argh. Typing up why that's not right , I might have understood why it is. I need to go away and do the sums on what happens if you project a squares 1,2, 3 & 4 pixel widths of white or (e.g.) red light offset left/right by 1/4 pixel and up/down but 1/4 pixel.

Possibly my head will explode before I get to the answer.