#550|MONOCHROME THREAD|POST YOURS|16Jul2021-23Jul2021

Started 2 months ago | Discussions thread
JimH123 Veteran Member • Posts: 3,132
Re: just tried bypassing the debayering on pp

ivan bayu wrote:

JimH123 wrote:

I will show an example of turning off debayering. First, here is an example. I have cropped out a red rose from an image.

Using RawTherapee, I have chosen mono, instead of using a debayering algorithm. Note that in this case, RawTherapee is choosing mono instead of just turning a debayered color image into a B&W image.

Next, I am going to pick the far right petal where there is a constant color and blow it up bigger. Notice the 3 different levels you see. Some are the values seen by red covered pixels, some from blue covered pixels and some from green covered pixels. You image does not show this, so your image is not really debayered. But we do need a definition of what DarkTable means by Bypassing.

OK, I found what you are doing in the dark table manual. See:

Notice that it says that it says that it discards the color information during the Demosaicing Process. This is a fancy way of saying that it is turning the image into a B&W image. But there was indeed debayering that took place. And by the way, debayering and demosaicing both mean the same thing.

hm... i still don't get it for the most part of it...

alas, as i said before, i'll do more test. and study more...

Carefully look at the samples I have provided and it will start to sink in.  Remember for a color image, each pixel in the image you look at has to have a red, a blue and a green value.  But when the image was captured by the camera, it started out as a bunch of separate red pixels values and blue pixel values and green pixel values.  Through some mathematical algorithms, each pixel is taken (let's suppose a red), and to get the green value, it needs to average together some green pixels around it and the get the blue it needs to average together some blue pixels around it.  There are lots of various different algorithms written to figure out how many pixels to average and under what conditions.  Some are designed for the best color rendition (at the cost maybe of fine detail) and others (such as used for astroastronomy for instance) wants best detail and is OK with poor color rendition.  In fact, RawTherapee offers about a dozen demosaicing algorithms to pick between.  And astro software I use has yet another.

As for a mono sensor, there is no need to do demosacing.  Every pixel is ready to use as captured in the RAW image.  It offers the best detail of all.

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