when using PS, is it better to de-saturate or use greyscale?

Question

when making something b+w. i notice that greyscale shrinks the file size...

i use duotone alot so am in the habit of just using greyscale. i notice though that the print qualtity is never that bad

Answer 1

When you desaturated you are staying in RGB mode. And beside the straight desaturated, there's also Hue / Saturation (saturation slider bar).

Using desaturate (or saturation slider bar) you can have levels of grayscale (like faded color photo) and add color (like those pic where everything is B/W except lips, etc.)

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The only time straight greyscale is better is (a) file size matters (b) you do not need any color at all (c) doing duo-tone - like yourself.

Answer 2

I usually use the b&w gradient map instead of desaturate or greyscale. Or the channel mixer. but I find the gradient map and then adjust levels works great for a print.

Answer 3

Personally, I would rather desaturate and keep the layers. If file size is a problem, then follow fotoace's suggestion.
Not sure how much PS experience you have, but Photoshop is one of those applications that has several solutions to one problem and any one of them might be applicable to yours.

If you desaturate, go to the levels and make your adjustments for lights and darks there. Using contrast mode makes the whole picture muddy so I don't use it at all.

Answer 4

Neither.

The best way to convert color to B&W is to use the Channel Mixer, which lets you simulate B&W film photos taken with just about any color filter.

Try these tutorials:
http://www.cambridgeincolour.com/tutorials/color-black-white.htm
http://www.luminous-landscape.com/tutorials/b-w_better.shtml
http://photo.net/equipment/digital/editing/bwconvert