Convert an Image to greyscale and its Histogram

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den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: Convert an Image to greyscale and its Histogram

Postby den » July 9th, 2017, 11:44 pm

...
Building a color line *.cln file from a preference source...
Screenshot (7).jpg
Screenshot (7).jpg (231.01 KiB) Viewed 177 times

Notes:
1) the Readout Tool values for RGB are in percentages need to be converted to decimals when used for the ^.cln text file.
2) color 0 is black and color 4 is white. Choose at least three other RGB colors with approximate Luminance or Value tones of 25, 50, and 75% respectively. Values do not need to be overly precise but can be.
3) Text "color n" line format: Luminance or Value tone value; Red value; Green value; Blue value... ...values range from 0.0000 to 1.0000 [00.0% to 100.0%]... ...It is usually easier to switch the Readout Tool to HSV and find a location at a 25, 50, 75% Value, then switch to RGB to get the color values.

Applying the *.cln file with Tint transform...
Screenshot (9).jpg
Screenshot (9).jpg (154.23 KiB) Viewed 177 times

Notes:
1) When using the Tint transform, I have not found it necessary to first extract a BW channel image as the Luminance channel image seems to be auto extracted, then the *.cln applied.
2) Move the "color n" points from their original or equal spaced positions to reach a preference while monitoring an updating Preview... ...this is the same as moving curve control points to increase/decrease contrast between the "color n" points.

...den...

Marpel
Posts: 288
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Convert an Image to greyscale and its Histogram

Postby Marpel » July 10th, 2017, 12:12 am

Den,

Excellent explanation. But a question for clarification.

For color 1, why did you enter 0.2510 (as opposed to just 0.2500) and 0.1960 and 0.2510 (rather than 0.2000 and 0.2550 as reflected in the readout tool)?

Man, I got to tell ya, some of this under-the-hood stuff can be quite confusing (and daunting), but your tutorials are always laid out so things are much easier to grasp. Your continuing contribution to this forum is to be applauded.

Regards,

Marv

den
Posts: 612
Joined: April 25th, 2009, 6:33 pm
What is the make/model of your primary camera?: Canon EOS-350D/Fuji X100T
Location: Birch Bay near Blaine, WA USA

Re: Convert an Image to greyscale and its Histogram

Postby den » July 10th, 2017, 12:48 am

...
The text file shown was done some years ago and I could not precisely duplicate the Readout Tool on the source image for the current posting, so chose readings that were close... ...sorry for the confusion. For practical purposes only the first two significant figures really count... ...the rest will get lost in rounding or imprecise positioning of the transform sliders or control points...

...while the value itself need not be precise, its format in the text file has to be or the file will not Load and work in the Tint transform...

...den...

Marpel
Posts: 288
Joined: September 13th, 2009, 3:19 pm
What is the make/model of your primary camera?: Nikon D810
Location: Port Coquitlam, British Columbia

Re: Convert an Image to greyscale and its Histogram

Postby Marpel » July 10th, 2017, 6:49 pm

OK, thanks Den.


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