Technique 1
Using the Channel Mixer adjustment layer, select:
Layer>New Adjustment Layer>Channel Mixer
Thenanewlayerwillappearontopofyouroriginaland
thechannelmixerboxshouldappear.Withinthisboxyou
willseeaMonochromeoption,withatickbox.Selectthis
to make the layer monochrome.
Therearethreecoloursliders–Red,GreenandBlue–each
with percentage number next to it. Photoshop will
automaticallyloadintheratiosofRed 40 percent,Green
40 percentandBlue 20 percent,anditisworthmovinga
fewaroundtoseethelevelsofchangestheymake.When
moving these to their required levels, the photographer
must ensure that the levels all amount to 100 per cent.
Ifyoufindthatmostofyourworksitswellwithcertain
levelsitmaybeworthloadingthisasapreset(icontothe
toprightoftheAdjustmentLayerbox),andthenyoucan
tweak it afterwards as you wish.
Technique 2 (a little more versatile than Technique 1)
Again using the Channel Mixer adjustment layer, select:
Layer>New Adjustment Layer>B&W> New Layer
(click yes)
Youwillthensee theblackand whiteselectionbox, as
withTechnique1.Hereyouwillfindsliders,butthereare
more here, six in total, to allow more control.