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12-12-2009, 01:04 AM   #1
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Unprocessed Bayer Array Picture?

Is it possible to render a picture from a RAW file that has absolutely no processing whatsoever? I think it would be fascinating to see exactly how the image was captured by the sensor, with the Bayer array intact and un-processed. I realize it may not be a pretty result, I'm just curious to see such a picture and examine it closely.

And I'm not referring to an unprocessed grayscale picture. I can do that easily with dcraw with the -D option. I'm referring to a picture that shows the RGGB locations too.


Last edited by GoremanX; 12-12-2009 at 01:11 AM.
12-12-2009, 01:51 AM   #2
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I think you have answered your question by using word render.

rendering (plural renderings)
1. version; translation.
2. sketch, illustration, or painting.
3. returning; giving back; assigning; making; translating; surrendering; affording.

That is, at the moment you decide how to display the image, your'e doing some sort of processing.
Another thing is that you'd need a HDR monitor, that can display true 12...14-bit image with a brightness range allowing to precieve such fine tonal graduations.

But if we take a more practical and simpler approach then yes you can. If you've been following tr13 attemts with Pentax firmware, at one step he has provided commands to dump varios stages of RAW file, before most basic noise reduction, bayer processing and similar.

Then there is another question. What does this grayscale picture represents and if the grayscale picture does not suit you, what do you expect to see? Each pixel having the tint of its bayer filter?
12-12-2009, 12:14 PM   #3
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QuoteOriginally posted by GoremanX Quote
Is it possible to render a picture from a RAW file that has absolutely no processing whatsoever? I think it would be fascinating to see exactly how the image was captured by the sensor, with the Bayer array intact and un-processed. I realize it may not be a pretty result, I'm just curious to see such a picture and examine it closely.
I think GordonBGood once posted something like that over in dpreview. It was very green.
12-12-2009, 12:50 PM   #4
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QuoteOriginally posted by ytterbium Quote
Then there is another question. What does this grayscale picture represents and if the grayscale picture does not suit you, what do you expect to see? Each pixel having the tint of its bayer filter?
Yes. Again, this isn't for artistic value, I'm just curious.

So I did it myself. I made a Bayer array rendering of a picture from my K7. It's made up entirely of RGGB pixel groups with the appropriate luminance values applied to each pixel.

Since my monitor can't display this many pixels on-screen at the same time, the colour looks completely different at different levels of magnification. It only looks "right" at 100% or higher. Scaling it down would mess up the Bayer array. The only way to make it smaller and retain the Bayer array is to crop it. I made a crop here:
http://www.projectgmc.com/temp/pentaxforums-uploads/bayer-array-cropped.png
(I'm not displaying it here because I don't want to waste my server's bandwidth everytime this thread is loaded, but feel free to click on the link)

Here's what I did to make it:

I exported the picture as an unprocessed 16-bit grayscale using the -D option of dcraw. You can clearly see the 4-pixel groups in this picture by viewing it at 100% or more. I made up the Bayer array by looking at a mostly-white section of the picture's sky. I assumed that the "medium" brightness pixels were green (since there were twice as many as the others). The section of picture I looked at is somewhat blue, so I assumed the light-coloured pixels were blue. And that left the rest of the pixels as red. I then applied a layer mask over this grid array using the unprocessed grayscale image as the mask, which assigned an appropriate luminance value to each pixel.

Unfortunately, my PNG is only 8 bit, so a lot of the luminance nuance is gone from the original 16 bit image that dcraw created.

As Marc mentioned, it does have a very green cast to it. But I find it fascinating to look at, especially zoomed in a lot.

12-12-2009, 01:32 PM   #5
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That's really cool. Thanks for that!
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