I got asked quite a bit. My initial reaction was to do it in Photoshop, using the layer blending mode. Snapseed is just as good. This feature is called DOUBLE EXPOSURE.
First of all, you need a layer to superimpose on the original photo. You can search for “lens overlay image” online.
Step 1 – Open the photo in Snapseed
Step 2 – Tools > Double Exposure
Step 3 – Select the overlay image from library
Step 4 – Blending mode > Lighten
Step 5 – View edits > make adjustments
In the demo video below, I have added “Vintage” and “Glamour glow” to enhance the effect.
