Here I want to demonstrate a quite simple method of achieving a double exposure effect. I am using Photoshop, but the same techniques should work in most good graphics packages.
First I open the two images that I am going to layer together:-
I should mention at this point that it is important that both images are the same size to avoid problems when aligning later.
Select the first image (in my case Figure 1) and right click on the ‘Background layer’ in the Layers panel – see Figure 3:-
Select ‘Layer from Background’ in the menu which pops up, this will open a dialogue box giving you the option of naming the layer, it defaults to Layer 0. I never bother renaming the layer unless I am doing something complex with a lot of layers and want to know what each one is for.
Next select the second image (in my case Figure 2), then select the move tool (at the top of the left hand toolbar – a cross with a pointer). Click on the image and drag it to the tab of the first image and hold there, without releasing the mouse button, until the first image reopens, then drag the second image onto the first and release. This will automatically create a second layer on the first image – ‘Layer 1′ as in Figure 4:-
Still using the move tool with layer 1 selected align the edges of both layers, the point at which it becomes important that both images are the same size. The move tool is good for a general alignment, but for more precise aligning of the edges the arrow keys are more useful as they can nudge the layer by one pixel at a time either up, down, left or right.
The next step is to reduce the opacity of the topmost layer (Figure 4 in my case) until you get a ghostly image with the bottom layer showing through. This is the point at which a little experimentation may be required as sometimes I have to bring the bottom layer to the top to get a good result, do this by simply dragging the bottom layer above the top layer in the layers panel (don’t forget to reset the opacity before doing this, as it is only the top layer that should have a reduced opacity). In this case I didn’t need to switch the layers and only reduced the opacity of the top layer to 30% as in Figure 5:-
All that then remains is to apply any editing that you require. In this case I simply cropped the image, applied a little noise reduction and sharpened it up a bit to produce the final double exposure.