Archived posting to the Leica Users Group, 2012/03/21

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Subject: [Leica] B&W Leica?
From: tgray at 125px.com (Tim Gray)
Date: Wed, 21 Mar 2012 14:57:44 -0400
References: <CAFuU78diOn7i883gyJeKFMQ7OYfC21OdMmHXhVfL9MyKgGM2dA@mail.gmail.com> <CB8E7277.106E8%chris@chriscrawfordphoto.com> <20120321174752.GA728@selenium.125px.com> <6FE59497-E5B8-4C9C-B88A-B4A9CB1F073C@gmail.com>

On Mar 21, 2012 at 10:58 AM -0700, Steve Barbour wrote:
>Tim,  maybe I'm confused, but if the human eye is more sensitive to 
>green, why more (rather than less) green pixels?

Note, I've not really looked into this much.  So I'm probably speaking 
out my butt a little bit.  But, our eyes aren't making the image, a 
sensor is.  So if you want to replicate what the eye would see, and the 
eye's sensitivity to luminosity, I would imagine you'd want your sensor 
to duplicate the spectral dependence of that sensitivity.  Which means 
loading up on green pixels.

The above is probably a gross over simplification.  Our luminance 
resolution is much better than our color resolution.  Our eyes have poor 
color resolution, particularly at the extremes of the colors we are 
sensitive to (red and blue).  And green sensitivity kind of plays proxy 
for luminance sensitivity.

Another factoid is that our eyes really aren't sensitive to RGB as we 
know it from computer imaging.  Quoting from wiki:

> For example, while the L cones have been referred to simply as red 
> receptors, microspectrophotometry has shown that their peak 
> sensitivity is in the greenish-yellow region of the spectrum. 
> Similarly, the S- and M-cones do not directly correspond to blue and 
> green, although they are often depicted as such. It is important to 
> note that the RGB color model is merely a convenient means for 
> representing color, and is not directly based on the types of cones in 
> the human eye.

The fifth plot on this page shows relative brightness sensitivity of 
'average' human vision (every person is different):
http://en.wikipedia.org/wiki/Colour_vision

There's also a bunch of interesting stuff on that and related pages.

Ok, so I just looked at Bayer's original patent.  Basically makes the 
above points, in a much more patentable manner :)


In reply to: Message from lew1716 at gmail.com (Lew Schwartz) ([Leica] B&W Leica?)
Message from chris at chriscrawfordphoto.com (Chris Crawford) ([Leica] B&W Leica?)
Message from tgray at 125px.com (Tim Gray) ([Leica] B&W Leica?)
Message from steve.barbour at gmail.com (Steve Barbour) ([Leica] B&W Leica?)