The confusing colour Green

[Jessun]

I tried to search on this but could not find an answer.

I read that the Bayer matrix of a typical DSLR or OSC has two green-filtered pixels for each red and blue one, and in litterature it's merely described as dealing with the human eye's higher sensitivity to green. That's pretty much all explanation there is on that...

Instinctively if I was to do a Bayer matrix I'd have less green pixels since we are more sensitive to it...

OK, bring on LRGB imaging (which is too complicated for me to even consider); I don't see a similar ratio in posted images i.e. twice the green exposure time, but rather a touch more red and blue.

The monitor again has a perfectly even colour pixel distribution...

Question: Why is green all over the place?

No actually the question is: What logical trap door have I gone through?

/Jesper

[Zakalwe]

Instinctively if I was to do a Bayer matrix I'd have less green pixels since we are more sensitive to it...

The response from the CCD is designed to mimic the human eye, in order to produce images similar to what the eye produces. Therefore it need to have enhanced sensitivity to green, hence more pixels (as each pixel is equally sensitive to R, G and .

Thats how I think it works, anyway.

[great_bear]

the question is: What logical trap door have I gone through?

The trap door is that you've assumed it's to do with the amount of green, rather than the accuracy of it.

[Jessun]

The trap door is that you've assumed it's to do with the amount of green, rather than the accuracy of it.

Ah, accuracy in terms of photon count, like brightness? (I'm feeling very basic and thick right now..) OK, now the ol' filter wheel, how does it achieve this accuracy, green given no obvious special treatment?

/Jesper

[Merlin66]

Bayer filter - Wikipedia, the free encyclopedia

Says it all.

[Merlin66]

Re RGB filters and mono CCD's

The response curve (Quantum Efficiency curve) of the mono CCD peaks in the green and automatically gives a higher response to this/these wavelengths.

[Jessun]

Merlin66, thanks for that, good link and good short explanation!

/Jesper

[ollypenrice]

...but it's an interesting colour, green, in astronomy. We all shoot it and then zap it with PixInsight or Hasta La Vista green. We're an odd lot. Apart from Thor's Helmet and the Owl I have never imaged a green object and consider it the root of all evil in colour imaging. It controls the magenta in blue and makes the reds look right - when it's behaving itself. But, as someone else pointed out, might we not be better using CMKY?

Olly

[blinky]

I was wondering this same question recently as well. I would like to actually know what Hasta La Vista Green does.... Does it simply remove the green altogether? In that case I'm loosing 50% of my pixels from my colour CCD!

[ollypenrice]

I was wondering this same question recently as well. I would like to actually know what Hasta La Vista Green does.... Does it simply remove the green altogether? In that case I'm loosing 50% of my pixels from my colour CCD!

No, it can't be doing that or it would turn all your blues into magenta. I guess it looks at where the green pixels are, and if they are not associated with certain levels of blue (and maybe red?) it dims or removes them. Truth is, I just don't know. However, applying SCNR to green in PI is not like dropping the green channel across the board. That is easy to verify.

Clever stuff!

Olly

[paraman]

...but it's an interesting colour, green, in astronomy. We all shoot it and then zap it with PixInsight or Hasta La Vista green. We're an odd lot. Apart from Thor's Helmet and the Owl I have never imaged a green object and consider it the root of all evil in colour imaging. It controls the magenta in blue and makes the reds look right - when it's behaving itself. But, as someone else pointed out, might we not be better using CMKY?

Olly

Its all to do with what we view on, as an example computer monitors have a black background, as do televisions, the combinarion of rgb makes white and the colours depending on the relative proportions. Paper on the other hand is white so rgb's not a lot of use on that, however cmy make black, well a very dirty close approximation anyway, k is added to make it better and is used in the colour mix. Unless you have a calibrated monitor the picture you see and the picture you print will look different because of the make up of the colours.

[michael8554]

Our eyes are tuned to the light of our sun, and they peak in green.

However, look down a telescope and unless the image is really bright you're only using your monochrome night receptors!

DSO's are illuminated by different-coloured stars, Ha emissions, etc, etc, so as Olly says, green is rarely present.

So you image with your colour ccd and only use half resolution red and blue. This is where mono ccd cameras excel, you get full resolution in any colour you want using the appropriate filters.

[Merlin66]

There are large spectral emissions in the blue/green from Nitrogen, Hydrogen beta and OIII - planetary nebula and some other emission nebula show them well....