Canon CR2 format and extracting individuals colours

[Guest]

I'm using maximdl which allows me to extract a single channel from the raw file. If I understand correctly there are 4 channels - green1, green2, red, blue. If I extract one channel the resulting image is half the size of the original. So my raw picture is 4290x2856 and the extracted image (one channel) is 2145x1428. It's the same whichever channel I extract. But why is it half the size and not quarter size since I'm extracting 1 out of 4 channels?

I'm doing this as part of my photometry work where the AAVSO say only use the green channel.

Cheers

Steve

 

[fifeskies]

It is a quarter of the area.

1/2 width x 1/2 height is equal to 1/4 the area

4290 x 2856 is 12M (approx)

2145 x 1428 is  3M   (approx)

 

the matrix is not linear GRBG , but forms as squares , alternate rows being GRGRGRGR and BGBGBGBG

 

 

 

Edited February 12, 2021 by fifeskies

[Guest]

Thanks, got that.