Blend modes to increase saturation and brightness

[Benjamin]

Often to get a lighting effect it's nice to have a gradient that starts with a base colour and ends with a colour that is slightly darker, and slightly more saturated.

A: S=80 B=100
B: S=100 B=80

Is there a blend mode that gives this result from a standard 'top' colour? Or can it be done from combining 2 blend modes?

What I want is something like this: to have a base rectangle of colour A, then to have another layer above it with a standard gradient, like white to black. Then if I switch the blend mode of the upper layer, and reduce the transparency according to taste, I want to end up with the gradient in the image. Of course 'multiply' is close to this, but doesn't change the saturation.

Doing it this way saves a lot of time as it would allow me to tune the colours in the bottom shapes without having to touch the gradients.

[urstwile]

What about a gradient map adjustment layer? In the menu Layer>New Adjustment Layer>Gradient Map.

I think this will achieve what you want.

[Benjamin]

I've never really used Gradient Maps but from what I can tell, they map grayscale equivalent values in an image to the colours you specify in your gradient. So it seems to be the other way around to what I want. Obviously it is pretty easy just to create the gradient directly anyway (just create 2 swatches, swap the Saturation/Blackness values etc). What I wanted was a way to set it up so that I can change the base colour of the object very quickly with a single click, and have the gradient change accordingly.

[urstwile]

Okay, I think I just didn't interpret your question correctly.

Hopefully this is correct. A Hue/Saturation adjustment layer with a gradient in the layer mask as the top layer seems like it achieves what you want. The ability to change the underneath color without affecting the gradient.

http://img103.imageshack.us/img103/9994/picture17wk.jpg

[Benjamin]

Yes, that seems to be the right idea, for Photoshop. How would I restrict the Hue/Saturation adjustment layer so that it only affects the particular shape below it? (Instead of the whole canvas)

Actually I use Illustrator most of the time and don't think Illy has anything like adjustment layers. I was thinking that I could just have 2 gradient shapes above the coloured shape, then switch the transparency mode of the first one to Saturation and the mode of the second one to Multiply. But somehow this doesn't seem to work so far.

[urstwile]

To have the adjustment layer affect just the layer directly below it, you would select the adjustment layer, then go up under the layer menu and select Create Clipping Mask, or hit Command (or Control for PC I think) G.

It will then show that adjusment layer as indented with a downwards arrow over the layer directly beneath it in the palette. All other layers will be unaffected.

I showed the adjustment layer affecting more than one to show you how the color differences didn't affect the gradient.

As to Illy, not sure if there's any way to do this at all in that program. I'll leave that up to other gurus. :D