1. Open your images as separate canvases in Photoshop

First up, open your images in separate canvases in Photoshop. You can do this easily by just dragging and dropping the files into the Photoshop home page. Or by going to File > Open and selecting the images you want. You can also load your files into a stack (where they open in the same canvas) by going to File > Scripts > Load Files into Stack, but you should only do that if you know your images are the same aspect ratio and exact dimensions (we’ll cover why below).

2. Crop and resize images to the same ratio and dimensions

Ideally you want your images to overlay precisely so there aren’t totally straight internal borders where a smaller image finishes. If you know what you’re doing, you can get away with having differently-sized images if you know where those gaps will be and can hide them with the other image. But to start off with, just ensure they’re the same size. 

It’s easiest if you do this before you load your images into the same canvas — if you loaded your files into a stack they’ll already be in the same canvas, where it’s a little more fiddly to change the sizes individually. 

So, with the images in separate canvases, crop the images to same same aspect ratio and then, on the larger image (pixel-wise) press Option + Cmd + I (macOS) or Alt + Ctrl + I (Windows) to open the image resize tool. Then reduce the larger of the two images to the same dimensions as the smaller one. We’ve used the larger image as it’s better to scale down a higher resolution image than it is to scale up a lower resolution one.

3. Convert both images to layers

Now, for each image, right-click the background banner in the right-hand layers panel (if you don’t see this, in the top toolbar click Window > Workspace > Essentials to reset your Workspace to default). Now select Layer from Background. If your images were .png or another format that supports transparency, they’ll already show as “Layer 0” rather than “Background” and you won’t need to do this.

4. Copy one image layer

Now, on one of the images (it doesn’t matter which) select the image layer in the right-hand layer panel and press Cmd + C (Mac) / Ctrl + C (Windows) to copy the layer.

5. Paste the layer into the other image canvas

Switch to the other image canvas and press Cmd + V (Mac) / Ctrl + V (Windows) to paste the copied layer into the second image canvas.

You now have a double exposure, you just can’t see it yet.

6. Select the top layer and adjust the opacity slider

Select the top layer in the right-hand layers panel and adjust the opacity slider downwards. This will start to make the top image more transparent, revealing the lower image, as you can see in the screenshot below. Play around with opacities until you’re happy. 

Also, ensure to experiment with which image sits on the top and bottom, as this makes a dramatic effect (as a general rule, you want the more prominent image on the bottom and the more transparent image on the top. Drag the lower image layer(s) to the top and change opacities again until you reach a double exposure you’re happy with. 

You can play around with adjusting the opacity of the base layer, too, which will result in a lighter background image and more dream-like effect. To start with, though, we’d recommend keeping it simple with a fully opaque base layer and a transparent top layer.

7. Go to Layer > Flatten Image

Once you’re happy, it’s time to condense the image by flattening. This combines the two layers into one, which finalizes your double exposure and locks it in. It also helps to shrink the image file size (useful given you just combined two potentially high-resolution image files). Select Layer in the top toolbar, then click Flatten Image.

8. Export your final image

Now, all there’s left to do is export your masterpiece. Click File in the top toolbar and export the image according to your preference.