Which is the best addition of 2 frames formula

[Tom OD]

Hi All,
I have not taken an image for months due to work commitments. I finally have some data to play with and I can't remember a thing.
I want to add two images together, and I don't know what is the best formula in pixel math.
0.5 A + 0.5 B
(0.5 A + 0.5 B)/2
0.5 *A + 0.5*B
(0.5 *A + 0.5*B)/2
etc....
I have Geralds tutorials somewhere in a link, should I just start again and get watching and taking notes.
Also anyone got a quick reference for the noise evaluation script. I can't remember what the J, and % bits mean when you run the script. There is no documentation in the process drop downs
Thanks Tom.

[Juan Conejero]

Use ImageIntegration and select each image twice. This way the tool will "see" four images and will allow you to combine them. Use average combination with noise evaluation weighting and additive output normalization (both options are enabled by default). This will give you an optimal combination in terms of SNR.

0.5 A + 0.5 B
(0.5 A + 0.5 B)/2

These are not valid PixelMath expressions because they lack operators between 0.5 and A and 0.5 and B.

(0.5 *A + 0.5*B)/2

This will average both images, but the result will be divided by two.

0.5 *A + 0.5*B

This will work as expected: the mean of both images.

Another possibility is:

(A + B)/2

and simply:

A + B

with the Rescale Result option enabled.

[Tom OD]

Thanks Juan,
I'll get straight back to work now on the image.
Tom.