switch to grey scale, but dont lose any color info, and switch back to color later?

[robertl69624974]

I was looking at a digital painter online. He somehow turned his entire piece greyscale (to check the values while painting) but didn't lose any of the color info. He then switched back to color. I'd like to figure out how to do this just so I can check the values and not lose the color info.

https://youtu.be/13CUb2deCmM?t=645     heres the time stamped youtube point at which he does it.

[davescm]

One way would be to switch to Lab Colour mode then use Ctrl+3 to view the lightness channel only (greyscale) and Ctrl+2 to view the combined Lab channels (colour)

Dave

[Chuck Uebele · Accepted solution]

From his comments, it's a proof set up in grayscale:

"Hey TAG, it is pressing ctrl Y . It is the shortcut for View - Proof Setup. To change it to greyscale you have to go there and change the proof setup to custom - Greyscale. Sorry that it is kinda confusing. Hope it helps :)"

[Trevor.Dennis]

Hi Robert.  It is not clear from the layers panel in the video, but a bit later in the video he mentions greyscale mode.  That is definitely NOT nondestructive though.  He does also mention Hue/Saturation, but we don't see a Hue/Sat adjustment layer, so he appears to be applying it directly to individual layers, which is totally OK in a drawing situation.

So the bottom line AFAICT is that we (I) can't tell from the video how he temporarily switched to greyscale, which means the world is your oyster.  You could put a Black & White adjustment layer at the top of the stack, and toggle it on and off as needed.  Or a Hue/Sat adjustment layer with saturation slider moved to zero.  Or channel Mixer layer with monochrom checked.  etc.

Of course, what you really usefull would be a single key Action that toggled between greyscale and colour, although there is not a lot of difference between hitting a key and turning an an adjustment layer one and off.

[rob day · Accepted solution]

To illustrate Chuck’s answer, here I’ve set the 2nd Info sampler to Proof Color, and have set the Proof Setup’s Device to Simulate to a Gray profile. Toggling Proof Colors on and off changes the preview between the Actual Color (RGB) and a Grayscale simulation: