How do you switch between normal colour and grayscale in Photoshop?

[HeiosArtCave]

Id like to use the ctrl + Y to switch between normal mode to grayscale, and back again, to check my values as I go. I've seen it done but I'm unsure how to set it up

Any clue how to do this?

[Trevor.Dennis]

Image > Mode > Greyscale

Image > Mode > RGB

[Trevor.Dennis]

Ahhh are you wanting to toggle temporarily?  I think so.

You could add an adjustment layer to the top of the stack, and turn it on an off.   B&W and Hue/Saturation layers would work.

Channel Mixer is good as it allows you to ajust tonal values according to colour

I can't think of a dedicated function that will do this by toggling on and off, but that's not to say that one does not exist.

[Stephen Marsh]

@Trevor.Dennis 

The OP mentioned using CMD/CTRL + Y which is View > Proof Colors

Therefore @HeiosArtCave you first need to use View > Proof Setup > Custom

Then select a Greyscale profile for the device to simulate, then you can toggle the softproof on/off via CMD/CTRL + Y

More here:

https://helpx.adobe.com/au/photoshop/using/proofing-colors.html

[Conrad_C]

I tried Stephen’s suggestion and it seems to work fine.

It is important for you to set up Proof Setup using the correct grayscale profile. Photoshop comes with several, and the OS might have a few more, and they represent different output conditions. For example, if your work is for the screen and never for print, do not select any of the Dot Gain grayscale profiles, instead choose something like one of the Gray Gamma profiles, probably Gray Gamma 2.2 unless you are targeting specific output such as broadcast video (2.4).

Also, since you mentioned checking values, if you want to do that precisely in addition to visually, use the Info panel. Set one of the sampler readouts to Proof Color to see the value of the pixel under the pointer. It reports the value after converting the color values to the current profile selected in Proof Setup. (In my example I chose Grayscale, but later realized that probably displays values in the currently active grayscale working space set in Edit > Color Settings, not the values for the currently active Proof Setup. So choosing Proof Setup instead of Grayscale is probably better for the purpose in this thread.)