One borrows an egg . . .
The way this works is simple and has been done before, undoubtedly. Put two to let's say ten images into separate layers in Photoshop. This can be done with the File menu in PS.
FILE > SCRIPTS > LOAD FILES INTO STACK . . .
Of course, at this moment you only see the top layer. But now the fun can begin. Adjust the opacity and blend modes of the different layers. It is important to keep the bottom layer at 100% opacity. There are many options in this general rule, so I'll share some of my experiences with Stacking.
One way might be to do the following calculation : 100 / (number of layers -1) and use the outcome of this calculation as the opacity of all the layers except the bottom layer, which should be kept at 100%. For instance : if you have 7 layers then : 100 / (7-1) = 100 / 6 = 16. Remember to calculate the part between the brackets first and then divide. Adjust the 6 top layers to 16% opacity.
This is just a starter. From there on try with adjusting the opacity and switching 'on' or 'off' of specific layers. You'll see that the resulting image can become quite different when using different layers to show or with different opacities. Remember though, that you do not have to use every one of the layers you have put there in the first place. Often leaving out one or more layers gives a better result. There is only one way in this game and that is experiment, experiment and then experiment some more.
Take a crossroad
Another way could be by using different 'blend modes' in which you blend a specific layer. I frequently use the following modes (in stacking) :
• Color Burn
• Soft Light
I also use inversion of layers. And of course also the Layer Blend possibilities (click on the layer thumbnail). And then there are 'masks'. These mask can come from more than the 4 channels of RGB (Red, Green, Blue, and of course the composite RGB). There are also the 3 channels of Lab (L, a and b) and the 4 channels of CMYK (C, Y , M and K). These masks are not only useful in stacking, but in any operation that involves masks. I have learned so much by also working in the Lab and CMYK color spaces (thank you Dan Margulis).
So the combination of the above techniques gives you an incredible range of possibilities. If you add adjustment layers as well, the world really expands. An idea might be to have two identical layers, the top layer set to 'difference' mode and with a clipping Curves layer (the layer affects thus only the top layer). By adjusting the Curves, you'll start to see the differences between the two layers.
Experience blend modes
I am still discovering new things with the many blending modes. The only mode I have not found any use for, is the 'diffuse' mode. Every other mode I have used, some much more than others, but the diffuse mode never. And it's not for trying.
One thing that goes for me is that I get better results when using similar images to stack. For me, wildly different layers do not work well. But who knows, I keep trying out stuff. I get an enormously amount of pleasure out of 'silly' experiments and every now and then something good comes out of it. Then you probably have an original idea. I also noticed that the bold are favored. As well as with my technique with the moving the camera, as stacking have grown roots because I was 'lucky' to start with the 'right' subjects.