On the Mac App Store
Photo
Sandwich
It blends two photographs into a double exposure. Two images, one result — the darkroom move made direct and fast.
It blends two photographs into a double exposure. Two images, one result — the darkroom move made direct and fast.
The darkroom knew this move: sandwich two negatives in the enlarger carrier, or expose one sheet of paper twice, and let the images fall into each other. Photo Sandwich does exactly that — it blends two photographs into a double exposure. Two images, one result. Nothing more.
The creative act isn't the blending. It's finding the right pairing — the frame that answers the other frame. That's the step no other app is built for, so it's the step Photo Sandwich is built around.
Two exposures, never more. That constraint is the app.
Pick a base image, drop a folder of candidates, and start browsing. Every candidate blends against your base in a live preview at hover speed — arrow keys walk the shortlist, the canvas updates as you go. No render button, no waiting. Finding the pairing is the whole game, so the browsing is built to be fast.
Stuck for a direction? Press Discover and Photo Sandwich randomizes the entire recipe — mode, opacity, mask, position — for a look you wouldn't have dialed in by hand. One Undo puts the previous look back. It's a slot machine for double exposures, and it's how the surprising ones show up.
When a look works, press Space to star it — and Photo Sandwich remembers the exact recipe, not just the pairing. Tweak the blend and star again: each keeper becomes a numbered variation you can flip back to and compare. Filter the browser down to just your starred pairings. When the shoot is done, Export All Starred renders every kept look at once, each from its own recipe, next to its source image. Your stars survive quitting and relaunching — and Session History goes further: reopen a past selection session on the look you kept, so a pairing you starred last week is still one click from where you left it.
Screen for the classic double exposure — additive light, the way two negatives stack. Multiply for a film sandwich. Overlay and Soft Light for contrast and texture. Linear Dodge for physically accurate addition. Cycle modes and presets from the keyboard and watch the result change under your hands.
Then shape it on the canvas: drag to move the overlay, Option-drag to rotate, pinch to scale — directly on the image, rendered through the real pipeline, not a fake preview. Set base and overlay opacity, and pull a luminosity mask so the blend falls only into the highlights or the shadows of the base. Double-click any control to reset it.
Two images, one result. The moment it became a stack of layers it would stop being this app and start being a compositor. The constraint is the identity — it's what keeps the tool fast and the decisions sharp.
On export, the full blend recipe — modes, opacities, transform, provenance — is written to the base image's XMP sidecar under the sw: namespace. A sandwich can be reopened and re-edited later, and the rest of the suite knows how it was made.
Sidecars are only ever updated, never created from scratch, and every other namespace is preserved untouched. Your originals are never modified. Nothing is uploaded, nothing phones home — it all happens on your Mac, offline.
Open exports straight from Photo Developer, combine them in Photo Sandwich, then hand the result to Photo Archive to catalog. The same XMP sidecar carries the work between apps — no re-import, no sync, no catalog. Output lands next to the original, named so it groups with its source.
"A photograph is a secret about a secret. The more it tells you the less you know."
Diane Arbus
Blend two photographs into a double exposure on macOS. Browse candidates against a live preview, Discover random recipes, star the keepers, and export them all — with the blend recipe saved to XMP. On the Mac App Store, $7.99. One-time purchase, no subscription. Requires macOS 26.2 or later.