new adjustment layer

I'm not really a computer savvy guy but I learn a thing here and there, mostly stuff that is relevant to what I do and not much else. I've never played a video game but I have fiddled with photoshop a little. One little problem I've encountered is (and it doesn't happen often) what do I do with a washed out image if I want to paint from it. In this case I have an old slide, ca. 1950's, that's a little washed out. Maybe many of you don't have photoshop CS2 or whatever so this may not apply but I've figured out a little thingygizmo that really helps to enhance a weak image. Normally you would go to levels to boost the midtones or darks and that's a good start but if you go to Layer>new adjustment layer> you have a choice of levels, color balance, curves, etc and click on one, you get a little box. At the bottom is a a button that says normal, click on that and choose multiply. What that does is transparently layer a copy of the image on itself. You can mess with the values or the color balance of each layer and really get a full and more inspiring image. At left is the original image at the top, next is just adjusting the levels and that the bottom is the new adjustment thingy. It's subtle but makes a big difference as far as getting information into the washed out areas. I thought it was kinda cool.