Is there a way to view colour images (in Painter 2021) in grayscale?
Found one way: Photo Art Panels > Underpainting > Preset > Black and White
There should be a less recondite way of doing this. Why not have a single menu item for this useful transform?
One way I've seen this done is to do the following steps:
1. Create a new layer. Put it at the top of the stack. Name it something like "Greyscale"
2. Press Ctrl/Cmd+F to bring up the 'fill' dialog
3. Choose pure black to fill the layer (R=0, G=0, B=0). Ensure fill opacity is 100%. Click OK to execute the fill.
4. Change the composite method/merge mode of this layer to "Colorize"
5. Lock the layer
6. Hide/show the layer as needed to check your greyscale values.
Alternatively, if you are on Windows Aaron Rutten has a handy way to do this using a feature of the operating system: https://youtu.be/rhZZaJIcCqA
It may depend on your workflow which is best...
Brilliant. Thanks Stephen.