B&W Conversion method comparison

[photoken]

The recent Experiments about B&W Conversions were so informative that I decided to round out the discussion by examining PL's built-in conversions.

The sample image I used for comparison is available here:
https://www.pexels.com/photo/snow-mount ... lake-6941/
(Note to administrators: This image is released to the public domain under the Creative Commons "Zero" license, which means there are zero restrictions on its use.)

Starting with the original image:

B&W Conversion original.jpg

I applied these adjustment layers:

B&W Conversion layers.jpg

All the adjustments used only the default de-saturation; the Curves -- Lab adjustment had the left and right end points of the "a" and "b" channels lines manually set to 50%.

As a side note, the highlighted layer (using the Hue Editor in RGB mode) is the only method whose adjustment layer does not affect the values of the colour image when the adjustment layer's mode is set to "Luminance".

The next message will show the comparisons.

[photoken]

And here are the comparisons:

B&W Conversion samples 03.jpg

B&W Conversion samples 02.jpg

B&W Conversion samples 01.jpg

There are subtle differences, which was to be expected.

Hope this stimulates some discussion and your own experimentation!

[bkh]

As expected, you get essentially the same result for the same channel (colour model) used (apart from small rounding errors wich go away if you switch to 16 bit mode).

L channel (Lab model): Curves Lab, H/E Lab and Grey Mixer (Curves lab has a colour cast, probably you set a = b = 127 instead of 128?)

I (HIS): Curves HIS, H/E HIS and H/S

V (HSV): Curves HSV and H/E HSV

Y (YCrCb): H/E RGB (same as if you add a grey layer in mode "Colour", a missing method).

L represents all colours naturally, at least that's what the creators of Lab claim, judge yourself. Y is a simplified version of L which renders pure red, green and blue darker. Compared to L and Y, I darkens yellow/green/cyan and lightens blue, while V lightens all saturated colours. If you use the Hue Editor for grey conversion, then these differences can mostly be evened out using the brightness curve, so the choice of colour model essentially gives you a starting point for the conversion (In the Hue Editor, the brightness control in HIS and HSV has more "reach" than RGB and Lab mode, though. For example, you cannot lighten blue as much, don't know if this is intentional.)

Cheers

Burkhard.

[photoken]

L channel (Lab model): Curves Lab, H/E Lab and Grey Mixer (Curves lab has a colour cast, probably you set a = b = 127 instead of 128?)

I set the endpoints of the lines to "y = 50%". Whatever PL does with that is beyond my control....

Both Lab modes show the grays as distinctly cool, more so in the Curves example. I have absolutely no complaints about that, since I always prefer a cool gray.

It's interesting to see that the Lab modes have slightly more contrast and separation of tones in the greens and in the reddish-browns (in the hills in front of the background mountain).

Again looking at those reddish-brown hills, it's interesting to see subtle differences between the HSV results obtained using the Curves adjustment and the Hue Editor.

[photoken]

(In the Hue Editor, the brightness control in HIS and HSV has more "reach" than RGB and Lab mode, though. For example, you cannot lighten blue as much, don't know if this is intentional.)

That's good to know, and useful for editing control, for sure.