Black and White conversion styles (not all monochromes are born equal)

[dmstraker]

If you're curious about the differences between various black and white conversion methods, attached is a demo with several different styles.

The original is created from gradients across a rectangle, with RGBK going from white to saturated to black (tinting and shading). The other layers show different conversions (using a rasterised version of the original). You can explore the attached .afphoto file to see how this is achieved.

The bottom line seems to be that there are three different 'styles' of conversion:

• HSL desaturates colours and so all colours go the same shade of grey.
  • This is done by pulling the HSL S slider to the left.
  • It also means colourful images can become very bland when desaturated.
• The Black and White adjustment makes result pixels white in the left part of the gradient, where the colour is fading to white.
  • This can be seen if you create a fully saturated layer of any colour, add an HSL adjustment then a B&W adjustment. The layer goes white. Moving the HSL L slider right from the centre position does not change this. Moving it left from the centre gradually changes the colour towards black.
  •  A risk here is that some colours may burn out to white (a way to recover this is to introduce grey to highlights by turning down HSL saturation just in the area affected (Blend Ranges is easier than masking for this).
• The rest of the methods shown all have the same effect, though with each RGB colour changing at a different rate across the spectrum.
  • This is presumably because saturated colours actually have different luminance values.
  • It also helps explain why some people avoid HSL and B&W, preferring such as Document Greyscale or Gradient Maps (these offer greater flexibility).

black and white conversions.afphoto

[Alfred]

1 hour ago, dmstraker said:

HSL desaturates colours and so all colours go the same shade of grey.

I suspect that isn’t quite what you meant, Dave! If you set the saturation value to zero, you don’t end up with the entire canvas looking as though it’s been flood-filled with one particular shade of grey.

[dmstraker]

1 hour ago, αℓƒяє∂ said:

I suspect that isn’t quite what you meant, Dave! If you set the saturation value to zero, you don’t end up with the entire canvas looking as though it’s been flood-filled with one particular shade of grey.

Aye, you're right, Alfred. Unclear language. Fix implemented. Adequate?

It's a surprising effect anyway. I've just added a new video to my InAffinity YouTube channel showing the different effects of different methods of conversion to monochrome. Glowing praise welcome. Corrections appreciated.

[Alfred]

3 minutes ago, dmstraker said:

Unclear language. Fix implemented. Adequate?

I still see the same text as I quoted in my previous post! What did you change?

[dmstraker]

5 minutes ago, αℓƒяє∂ said:

I still see the same text as I quoted in my previous post! What did you change?

"The Black and White adjustment makes result pixels white in the left part of the gradient, where the colour is fading to white !"

refresh?

[Alfred]

18 hours ago, dmstraker said:

"The Black and White adjustment makes result pixels white in the left part of the gradient, where the colour is fading to white !"

refresh?

What’s to refresh, Dave? That part is about the Black and White adjustment, but we were discussing the HSL saturation adjustment.

[dmstraker]

On 7/6/2018 at 9:29 AM, αℓƒяє∂ said:

What’s to refresh, Dave? That part is about the Black and White adjustment, but we were discussing the HSL saturation adjustment.

Wups.

" HSL desaturates colours and so all colours go the same shade of grey."

In the example given, this does happen as each of the RGB colour gradients are linear from white to saturated hue to black. Yes, in an average image they will desaturate to different shades of grey, but the result can be quite manky, as in the video where I use a photo of flowers which mostly have the same degree of saturation.

[Affinity Revolution]

Very interesting. I've never closely examined the difference between HSL de-saturation and the black and white adjustment. Thanks for sharing!  

[uncle808us]

Thanks for the video very informative.

[BiffBrown]

A very interesting, and informative, video. I look forward to seeing the use of Gradient Maps in B&W conversion.

There is, of course, a further method for converting to B&W - the use of B&W LUT's (Look Up Tables), especially for Film Simulation. See 

for more information.

 

Regards,

Biff