Gradient map "to Transparent" problem

I want to use Gradient Map to make the black stuff blue and the white stuff transparent. But I don't seem to be able to make the "Background to Transparent" do what I think it should do. I never get anything transparent; it always ends up as opaque of some color I can never quite predict. What am I missing here?

A bit more info for us to help you better? <g>

Are you working on a layer? Is that layer empty?

Did you check the help file under "Gradient Editor dialog box"?

I'm working on a layer that contains a drawing in white on a black background. I would like the black to be transparent and the white to become light blue (the Foreground color), and the greys to be semi-transparent blue.

I checked the Help file and so far as I can tell it describes what I want to do; to me it isn't doing what it says. I'm in 8-bit RGB mode.

I guess you need two steps

First, to get the transparency, copy the image into the layer mask. Black then means hidden (transparent), white means revealed (opaque).

Second, change the color to blue. This could be done with a new blue layer on top, blending mode set to multiply.

Sven

As there are always more ways than one to do anyting in PS here is the obligatory alternate method:

Create a blue fill layer, add a layer mask to it and copy the B&W image into the layer mask.

Why not Map your black to an unwanted, absolute colour such as yellow? Make a final composite from a gradient map adjustment layer and delete all the yellows on the composite layer or mask after you finish mapping the rest. Here's how:

Start with Layer > New layer adjustment > gradient map; then choose the 3rd --white to black gradient. Double click the gradient itself, in order to Bring up the gradient editor.

Add a middle color stop so that you have 3 Color Stp[s; rather than just the two.

Turn the highlight colour stop to Navy. Turn the mid-stop, light blues, (see location 50% and adjust "O's on either side to suit).stretch the middle blue to what you prefer.

Set your 3rd stop (shadows) to YELLOW and move the "O's" close to get blacks.

Make a comp of the adjustment on it's own layer then delete or mask out the yellow which reps. black from your original image.

I learned to manipulate colour this way from a "PSWorld Dream Team Book" re: Daniel Giordan's tute "Explorations of Organic Symmetry".

HTH. It's pretty straigh formward if you already have your colours picked out so you don't get carried away colour tinkering.