Digital Photography 101: Raw File Demosaicing 

Cheers Buddy, we aim to please !

Glad it helped!

Thanks Jeff 😀

Glad you enjoyed it!

Glad it was helpful!

Glad it was helpful!

Hi James, glad the video hit the mark for you! The 'unmosaiced' image is an export from Raw Therapee which gives you the option to view the unmosaiced file - something you may, or may not, find useful. Lightroom has a single fixed demosaic algorithm, whereas Raw Therapee has multiple single, and mixed demosaicing options - hence I'm such a big fan of it!

Cheers Frank!

Thank you!

Thank you

This might help: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LWxu4rkZBLw.html

All demosaicing algorithms in all raw processors average out G1 and G2 channels into one single green channel. This is the only way a digital sensor can begin to represent human vision, since human eyesight is twice as sensitive to green, as it is red or blue.

@@AndyAstbury Thanks for answering! That's what I also think - that values fron G1 and G2 shoud be averaged. However, in astrophotography, the situation looks different - first, there are raw files, all black and white, before debayerization. After debayerization, before applying any sort of data stretching, histogram for G is about twice as far to the right as are the R and B histograms. When one applies white balance correcrion during debayerization the G histogram falls where it should be, i.e. between B and R (as it is in jpg files generated by a DSLR when shooting astrophotos - there is almost always less green than red in the night sky, and even less blue). I was always wondering why, right after debayerization, but without WB application, unprocessed astrophotos have this green tint (result of G values about twice as high as R and B). It looks as if G1 and G2 were added, not averaged. But I'm talking about debayering raw astrophotos in astronomical software, like Deep Sky Stacker or Siril. They generate debayered images with green tint. On the other hand, programs like RawTherapee, designed for daytime photography, don't make this green tint, because they apply WB setting on-the-fly, during debayerization (I think... :) ).

White balance on astro can be tricky if you dont add in a master flat field frame to the mix in SLS. And what bit of light the camera sees is blue! If there are greens in the sky it could be the natural phenomenon of air glow, so I try to leave it in.

Actually made in Raw Therapee with the demozaicing turned off, exported out as a TIFF then brought into Lightroom for illustrative purposes!

Hi Carlos - let's break it down. Orange is basically a mix of Red, which is a primary colour, and Yellow which is a secondary colour and a mix of Primary Red and Primary Green. Does that answer your question?

@@AndyAstbury so all of the secondary colors are extrapolated by the processor or is there actual mixing of wavelength going on. Sorry to burden you with my questions I ain't the smartest fellow walking the world.

@@carlosenriquez2092 No worries! NO, the only things recorded by the sensor are luminance values of pixels sitting below red, green or blue filters. So a raw file is a mosaic of various luminance values only. It's the demosaicing algorithms that work everything out and invent the missing colour data. But the whole imaging system on a computer is additive so it behaves like real light, so where primary channels overlap they mix to the secondary and tertiary colours.

@@AndyAstbury thank you now it makes sense. Like I said not a brilliant t fellow here thanks for your patience.

@@AndyAstbury just picked up a used D700 and I can't believe how buttery and silky the pictures it renders out are and it's a fifteen year old dinosaur. 😳

Hi Alex, as I say, it's done by the demosaicing algorithm by interpolation of missing colour values from adjacent pixels that are filtered with the missing colours. Different demoz methods use different interpolation patterns. Hope that helps explain things!

Thanks for putting me straight there Doug 😀

defending your name xDD