Open Document

So here is where we left of from the previous tutorial. In the next steps we will ensure that our image is true grayscale by adding a Channel Mixer adjustment layer, but first, lets get an idea of why our image is not yet grayscale.

Info Tab

Scroll over to the top right of Photoshop to the Navigator tab and scroll over to the third one and click on the "Info" tab.

Info Readout

1. location of mouse pointer.
2. RGB readout in Info palette.

Now with the Info palette open, scroll over your image and find a black area. As you do this, take a look at how the numbers change in the RGB readout. Here you can see a readout of R,G,B, = 11,10,12. When the numbers like this are not even that means that the image is not a true grayscale. The numbers will be all even for the RGB readout when the image is in true grayscale. So this is showing us that there is a little bit of a color cast in the image still. Lets go ahead and change that which we will do in the next steps.
Also remember that it is fairly common for scanners to scan in black in white negatives in this manner, so it's always good to make a Channel Mixer adjustment layer as we will do here in a moment so that you know for sure that you're image is true grayscale in Photoshop.

Locate Channel Mixer

Now we'll go ahead and add that Channel Mixer adjustment layer. Go to the top of Photoshop to the Menu bar and navigate to Layers > New Adjustment Layer > Channel Mixer...
This will add a new adjustment layer to your layers palette named "Channel Mixer" and will pop open a Channel Mixer dialog box for you to edit some settings in.

Second Way of Locating Adjustment Layers

Please take note that there is a second way of locating new adjustment layers, even the Channel Mixer, which is down towards the bottom of the layers palette. It looks like a little half circle icon and you can locate your adjustment layers here as well as the previous method.

Channel Mixer Pops Up

Now once you've clicked on the Channel Mixer adjustment layer, this is what the dialog for it will look like and it will pop open at the same time the new adjustment layer is made into your layer stack. This is how it looks at it's default settings. Lets make some adjustments now to it and achieve that true grayscale image that we are after.

Monochrome

First thing we'll want to do is click on the Monochrome check box towards the bottom left of this dialog box. You'll notice that in the Output Channel towards the top that the Red changes to Gray. We've just now changed this image to grayscale.
Next we will adjust the sliders for Red Green Blue under the Source Channels section. Remember that the Reds are for the high contrasts, Greens are for the mids and the Blue slider is for the noise and darker areas.

Basic Version

Now we've already adjusted the sliders and you may do the same and match the setting that are shown in the image here to your document. Basically we brought the Blue slider down to zero, and then adjusted the Red and Green to achieve a basic version for grayscale and that totals out to 100%. This basic version is a great starting point and will give your image some nice grayscale values. You can play around with adjusting more if you want. For instance try lowering the Blue slider, and upping the Green to compensate so that the Total still equals 100%. Be careful when doing this though.
Red, Green, Blue - 30, 70, 0, is a good place to start though for all beginners.
Finally, click OK to finalize this Channel Mixer adjustment layer.

Finish

If you take a look now to your Layer palette you will see the Channel mixer has been added to your layer stack. The Channel Mixer layer is a non-pixel layer unlike the duplicate and original layers which do contain pixels. Remember that any new adjustment layers that you add to your document will come pre-built with layer masks. These can be very useful later on and we will go over them in later tutorials.
*End Tutorial*

RGB Gray - Channel Mixer Adjustment Layer