Ok… I’ve been playing around a bit. (again)
My question is (somewhat based off another thread here with @Joanna in regard to the Channel Mixer, Working Color Space and Filters.):
What should my expectations be in regard to the behavior of the Channel Mixer on an image that has been converted to B/W? It seems to me, regardless of the WCS, the effect on the image is minimal.
To be transparent, I am comparing the Channel Mixer on a B/W image in PL directly to the Color Sensitivity sliders in the B/W panel of C1.
While I realize that its very likely these two panels do not work the same (and that’s ok), I AM trying to understand what, if anything, the Channel Mixer does to B/W images in PL8.
I REALLY like having the ability to affect the underlying colors in my B/W images… if the Channel Mixer doesn’t do this in PL8, is there another way of doing the same thing?
This is precisely what the channel mixer is designed to do. From the PL8 user guide:
The Channel Mixer lets you adjust and fine-tune color and black & white pictures according to your taste by acting on the additive colors (red, green, and blue) as well as on the subtractive colors (cyan, magenta, and yellow).
You can think of the Channel mixer as a set of fully-configurable filters. Although the filters in the Filter palette are limited both in hue and intensity, the Channel mixer lets you create any combination of colors at any level of intensity.
To use the Channel mixer, you will need to evaluate which channels are too bright or too dark, and then move the corresponding sliders in the desired direction. For example, if your image contains yellow elements, you can move the Yellow slider to the left to darken them, or to the right to brighten them.
I did a quick test with a JPEG and a RAW image. For me, the channel mixer and filters seem to be working as they should on a color image converted to B&W. They should work regardless of the working color space. (I use DxO Wide Gamut.)
Both Channel Mixer (CM) and HSL work on certain hue ranges. The difference is that CM is applied before rendering and HSL after. So, if you choose B&W rendering, HSL will have no effect (grey has no Hue) and you are left only with CM and WB as substitutes for glass filters (well, you can cook some DCPs or LUTs instead, but…). Note that photos often have very small number of pixels in a given hue range, so the effects of CM in some channels may be non-existent.
I’ve never done any “research” on CM, just used it a bit like a monkey. It works also on RGB files so you may try it on some “16 millions of colors” or a color wheel tiff, to see how it affects particular Hue/Sat combinations. It seems it works “per pixel” – the neighboring pixels are not taken into account, so it is a very simple tool with small performance penalty.
CM is primarily meant to be used with B&W, and I use it with color images only when I’m lazy and then very sparingly, e.g. max -10 Green or Yellow to tame the vibrant fresh grass in the landscape. Normally such corrections for color renderings should be done in HSL, but that takes more time, if you want good result. CM for color may give sharp transitions and very ugly results, if overused even slightly.
Personally, I would like a second instance of HSL, which would be applied before rendering. Maybe HSL should be simply applied automatically before rendering, if B&W is chosen. That would give me enough control for B&W conversion, e.g. for close up portraits. I’m not a B&W expert, though, just my 5 cents. The Working Color Space thing is another story, which should be addressed by DxO, imo.
Not exactly. If you have a FilmPack license, you also have the Filter palette.
It was, several years ago. If there’s a significant difference in behavior when the WCS is changed, it’s a bug. Fact is that filters do work a bit differently with WCS, but perhaps in a way that can be accounted for by color range compression prior to applying the filter. When they break entirely because of the color rendering setting, then there’s something that most definitely needs to be fixed. (This has been noticed from time to time.)
Yes, forgot to mention that, maybe because there’s a thread by @Joanna about it and WCS. If Red Filter slightly lightens the sky with intensity going from 100 to 200 with WCS=Wide and heavily darkens it on the same photo with WCS=Classic, it sounds like a bug. DxO should either fix it or explain it in details.
Channel Mixer acts differently, depending on how you got B&W.
If you try different ways to convert to B&W, you’ll find out, in which cases channel Mixer will work.
One of my favourite ways to B&W is to use the HSL tool. It can be used to change tonality of each channel AND each channel can be tailored too by making it wider or narrower or moving edges. Here’s a video with some OTT changes:
At the end of the video, I re-add some colour. This can be used for creative purposes like a B&W image of a poppy field - and only the petals are coloured. The example used is a lot more boring than that, alas!
