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Author Topic: RAW to black and white  (Read 1037 times)

lostfeliz

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RAW to black and white
« on: October 04, 2013, 08:51:44 PM »
I had a shoot yesterday at an artist's studio. The photographs are to be printed large and wallpapered as part of the installation for a show of his work.

Here's a description of my dilemma or question.

Camera sensors usually have four light sensitive pixel for each de-bayered pixel. I think often, it's two green, a red and a blue. I know that Red has released a black and white camera that treats each pixel the same to give extra resolution. Is there anyway to process a RAW image from a 5d3 to make use of those pixels individually? And increase the resolution. I know it might be impossible to adjust the greens, blues and reds to make a usable image, but wanted to see if there's any software that attempts anything like this.

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RAW to black and white
« on: October 04, 2013, 08:51:44 PM »

ajfotofilmagem

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Re: RAW to black and white
« Reply #1 on: October 04, 2013, 09:53:00 PM »
Using logical reasoning, we can imagine each individual pixel RGB being read and not passing for the demosaicing process, which would result in three different values per pixel. Imagine now that an object is pure red, and so green and blue channels have signal near zero. When viewed closely, the image of this object (which was red) would be formed by a light spot (red channel) and two dark spots (green and blue channels). The result would probably be something like film grain black and white. Do not believe there would be a gain of sharpness, but one accrued granulation, which might seem more organic, or artistic.
« Last Edit: October 04, 2013, 10:17:37 PM by ajfotofilmagem »

brianboru

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Re: RAW to black and white
« Reply #2 on: October 04, 2013, 10:30:47 PM »
The camera's sensor is made up of sensels each sensing one of red, green or blue.  Placed in a grid of 4 sensels (2-green, 1-red, 1-blue).   Conceptually the value of the pixel is the value for each cluster of 4 pixels but the clusters are not unique, the pixel to the right is sharing half of it's sensels with the one to the left - and half with the one above, and half with the one below and half with the one to it's left. 
Peek at the picture at:

http://www.photozone.de/sensor-types

So you are getting a full resolution picture where the number of pixels in the picture equals the number of sensels on the sensor (less 1 column and 1 row of sensels to account for the edge condition.)

So the short answer is no - given a Bayer sensor, you can not get better resolution than you already are.   

Taken to an extreme. If you took a picture of a perfect red wall with your 5Diii - only 5.6 Million red sensels recorded into the raw file would have a value while the remaining 16.7 blue and green sensels would had no value.   It's the Bayer algorythm that lets that combination be interpreted as a consistent 23 Megapixel image of a red wall.
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Drizzt321

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Re: RAW to black and white
« Reply #3 on: October 05, 2013, 12:10:51 AM »
There is 1 production camera that I am aware of that doesn't have any sort of CFA, and it's the Leica M. So it only shoots B&W, unless you colorize it in post. But it's $8K body only.

Now, there are one or two services out there that will take your camera (or one they buy for you) and remove the CFA and anti-aliasing screen and IR filter for you. However it's difficult, and chancy at best, especially if you have no experience doing it. It's pretty expensive to get done, but would do what you want. However then the camera is permanently modified, and if you remove the IR filter you then need to use filters to remove/only use the parts of the spectrum you want to photograph.
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viggen61

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Re: RAW to black and white
« Reply #4 on: October 05, 2013, 12:50:13 AM »
Camera sensors usually have four light sensitive pixel for each de-bayered pixel. I think often, it's two green, a red and a blue. I know that Red has released a black and white camera that treats each pixel the same to give extra resolution. Is there anyway to process a RAW image from a 5d3 to make use of those pixels individually? And increase the resolution. I know it might be impossible to adjust the greens, blues and reds to make a usable image, but wanted to see if there's any software that attempts anything like this.

A camera with a Bayer filter does not have four times as many light-sensitive locations relative to the nominal number of pixels. So your 5D3 with 22.3MP does NOT have 89.2 million light-sensitive locations! They do have a few more, so that proper values can be obtained on all edges, 23.4MP for the 5D3.

The RGB value for a given pixel is determined by the value of the pixel modified by the values of its neighbors. So, a red or blue pixel can register RGB green, because all the neighboring green pixels are saturated, and the red or blue pixel itself has a very low value.
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Re: RAW to black and white
« Reply #4 on: October 05, 2013, 12:50:13 AM »