Conversion of Color to Grayscale in Depth!

My personal preference is to start with raw data, avoiding the steps of transforming to RGB then converting "back" to Grayscale.

But many prefer to convert color images to grayscale. There are many ways to carry out that transformation and a few are usually offered in most Editors. However, those many ways can have quite different results, for example:

Notice how bad the ever-popular Luminance method (CIE Y) is compared to the others!

Which method above do you like and what method(s) do you use personally?

The full paper by Martin Cadik et al can be seen here:

cadik.posvete.cz/color_to_gray_evaluation/

Takes a while to download - many, many images!

I understand, Arvo,

Fig 6 came from a different paper by Cadik & Co. Can't find a link right now.

Here's the GIMP choices for simple de-saturation which I use for quick work:

The GIMP has some more drastic methods buried in my G'MIC plug-in ...

I don't know where all those fancy Cadik-tested methods can be found.

guess what method i use 😁😜

film

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thanks for sharing

oh

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Very nice pictures. I guess in camera conversion to B&W.

It's a good method if you want to see B&W pictures in your camera's back screen. But that method converts jpegs only.
If you are going to edit your photos later you have to shoot RAW+jpg. So you have a jpg for preview in b&w and an editable raw to make your picture.

There's many useful methods in RawTherapee to convert raw to grayscale, btw. This one converted in RT.

Also, there's a few in the GIMP:

As can be seen in the middle, their Color To Gray is a bit fierce! The other one is by HSV Value, which often works well compared to Luminance.

I seldom make grayscale pictures because I love colours so much. Sometimes I still do.
I used Channel Mixer in Photoshop to bw conversions.
This is monochromatic channel mixer in GIMP. It's called Mono Mixer.

Thanks, I gave that a shot - lot of green and reduced red followed by default Unsharp Mask:

Here's some screenshots from RT. There are many more methods and you can make your own tweaks in every method!

This is more natural in my eyes. I like smooth gradation. It's like documentary photograph in B&W film. In that case we used slight yellow filter with ( panchromatic) b&w film to avoid blue skies to burn out and to keep other colors in natural grey tone. You can do that effect reducing blue a little and maybe raising red and green a little. But why not to use more dramatic tones? In the first tomato conversion I imitated rad filter in film to make tomatoes almost white. In the last tomato example I used blue filter which made tomatoes too dark to my taste. I prefer channel mixer with arbitrary tweaks.

Depending on the camera, there may be a quality JPG inside the raw file. Canon has done this for years now.

I like the gradation to be that of the scene. So, if the scene contains a sharp edge, I would prefer the capture to render an equally sharp edge (no overshoots/undershoots). Not possible in theory, so let's say that an edge response where 10-90% takes 1.26px is as good as it gets.

www.falklumo.com/lumolabs/articles/sharpness/index.html

On the other hand, if the scene has smooth gradation such as a sky, then I would not like to see banding.

For my cameras (not Canon), the in-camera JPEGs are of a fixed quality, even when embedded in the raw file. They all have chroma sub-sampling, so are not of the best quality.

If I am trying for maximum image quality, I start with the raw file. From there, if I need a JPEG I can set the quality and subsampling as appropriate for the image destination. Rare, but FastStone Viewer can save a JPEG as RGB with zero interpolation and zero subsampling .... the ultimate JPEG quality!

users.wfu.edu/matthews/misc/jpg_vs_gif/JpgCompTest/JpgChromaSub.html

In my Sony 7RIV there's 1616x1080px jpg file embedded for preview in the RAW file.
I extracted the preview jpg from raw file. The camera was set to B&W. JPG was also b&w ( in rgb color space, but desaturated )
RAW did open as color picture in RawTherapee.

I don't know, but I guess there is also a small jpeg in Donald's 7m4 RAW files.

I don't think any JPG was really editable. You can do small edits.
If you do strong edits eg. color corrections or gamma corrections rising shadows, you decrease image quality.
The RAW file is much better starting point.

I agree. But the most important is that you are able to edit your picture in which way you like it.

Thank you for mentioning that chroma subsampling in JPEGs!

I checked my export settings in Gimp and RT. In both of them you can select very high quality settings.
Gimp manual tells there is no chroma subsampling at 4:4:4 setting. I use quality setting 100. I guess it means zero interpolation ...
Look: docs.gimp.org/2.10/en/gimp-images-out.html#save-export-image

In RT I also have Quality: 100 and Subsampling: Best Quality.

From the same picture I get the same file size in both editors with these settings.