Dissolve

What is a dissolve in film?

A dissolve is a transition in which the outgoing shot fades down while the incoming shot fades up over the same stretch of frames. For a moment both pictures are on screen at once, each partly transparent, and then only the second one remains. Editors also call it a cross dissolve, a lap dissolve, a cross-fade or, in British and broadcast usage, a mix.

It is one of the core film transitions of film editing, and it sits between the two most common ones. A plain cut replaces one image with the next in a single frame and says "now this." A dissolve takes its time and says "and then, a little later" or "and this is connected to that."

Mechanically, a dissolve is two opacity ramps running in opposite directions. At 24 fps a one-second dissolve uses 24 frames of each shot, and at the midpoint each image sits at roughly half strength. That has two practical consequences:

• It eats footage. The editor needs extra frames, called handles, past the cut point on both shots. If the camera stopped rolling the moment the action ended, there is nothing left to dissolve with.
• It creates a third image. Halfway through, the frame is a composite that neither shot contained. A good dissolve plans that composite; a careless one produces a muddy frame where two busy pictures fight for attention.

In a screenplay the transition is written as DISSOLVE TO: at the right margin, one of the few screenplay transitions writers still use regularly, usually to flag a jump in time.

Why do filmmakers use dissolves?

To show that time has passed. This is the dissolve's main job. Dissolve from daylight to lamplight in the same room, or from a young face to an old one, and the audience fills in the missing hours or decades. Editing has no cheaper or more readable tool for the passage of time. Saving Private Ryan (1998) pushes in on the eyes of an elderly veteran at a war cemetery and dissolves to landing craft heading for Omaha Beach in 1944: one transition crosses half a century and frames the battle that follows as remembered.

To enter a memory or a mind. Because both images coexist for a moment, a dissolve feels like thought, one picture surfacing through another. That is why it is the classic doorway into a flashback, and why long, slow dissolves feel dreamlike. Apocalypse Now (1979) opens with Willard's upside-down face layered over burning palm trees for so long that the transition becomes his state of mind.

To link two ideas. Put two shapes in the same part of the frame and dissolve between them, and the audience compares them. In Psycho (1960) the water spiraling into the bathtub drain dissolves into a close-up of Marion's eye, and one circle becomes the other. This matching dissolve is the softer cousin of the match cut.

To ease a move in space. A chain of dissolves carries the viewer on a journey without the jolt of cuts. Citizen Kane (1941) opens by approaching Xanadu through a series of dissolves, the one lit window holding its place in the frame while the fence, the gates and the grounds change around it.

To set rhythm and mood. Dissolves slow a sequence down. A string of them makes a montage feel wistful where the same shots joined by cuts would feel brisk. Overuse them and every dissolve becomes a small pause that drags the pacing.

Types of dissolves

The effect in your editing software is always the same blend, but editors use it in several distinct ways.

• Standard dissolve. A straight blend between two unrelated shots, usually 12 to 48 frames. It marks a change of scene with a softer punctuation than a cut.
• Matching dissolve. The two shots share a shape, a position or a movement: a drain and an eye, a candle flame and a sunrise, a spinning wheel and a clock face. Framing does the work, so it is planned at the storyboard stage.
• Same-frame dissolve. The camera stays locked on one composition and only the contents change: people appear and vanish, light swings from morning to night, a room fills with boxes and empties again. It depends on a rock-solid static shot, and it compresses time more precisely than any other device.
• Long dissolve. Stretched to several seconds, the midpoint lingers and the blend becomes a held superimposition. Use it for dreams, grief, memory and openings like the one in Apocalypse Now.
• Soft cut. A dissolve of 2 to 6 frames. Documentary and interview editors use it to smooth a jump in the same framing without pretending no time was removed.

How to plan, shoot and edit a dissolve

A dissolve is applied in the edit, but the good ones are decided on set.

1. Roll long. Give each shot three to five seconds before the action starts and after it ends. Those spare seconds are the raw material of the overlap.

2. For same-frame dissolves, lock everything. Heavy tripod, tape marks on the legs and the floor, the same focal length, manual focus, manual exposure and white balance. If the light is supposed to change between states, change it with lamps and flags, never with the iris, or the whole frame will pulse.

3. Compose for the midpoint. Put the detail of one image where the other is dark or empty. A face on a dark, plain background holds up under almost anything; two full-frame textures (foliage over crowd, water over brick) cancel each other out. Decide which image the audience should be looking at halfway through.

4. Balance brightness or design the shift. Dissolving from dark to bright feels like waking or dawn; bright to dark feels like dusk or loss.

5. Set the length by meaning. As a starting point at 24 fps:

• 2 to 6 frames: soft cut, smooths a jump without calling attention.
• 12 to 24 frames: a gentle change of scene.
• 36 to 72 frames (1.5 to 3 seconds): time passing, entering a memory.
• 4 seconds and more: the blend itself is the image.

6. Place it deliberately. Most editors center the dissolve on the cut, taking half its frames from each shot. Start it on the cut if the outgoing shot must finish, end it on the cut if the incoming action must start exactly on time.

Cross-fade: the editing-software name

Cross-fade is what most editing software and most sound editors call the same operation: the outgoing clip fades down while the incoming one fades up over the same frames. In the picture timeline the effect is usually labeled Cross Dissolve, and in Premiere Pro, Final Cut Pro and DaVinci Resolve it is the default video transition, a single keyboard shortcut away.

For picture, a cross-fade and a dissolve are the same thing. For audio, the word matters more, because the shape of the fade changes what you hear:

• Constant gain ramps both clips linearly. The combined level sags in the middle, so you hear a slight dip.
• Constant power curves the ramps so perceived loudness stays even across the join. It is the usual default for music and ambience.
• Short cross-fades of a few frames on dialogue edits remove clicks and hide changes in room tone without being heard as transitions.

Lap dissolve: the original name

Lap dissolve is the older, fuller name, and "lap" stands for overlap: the tail of one shot laps over the head of the next.

In the earliest films the effect was made in the camera. The operator faded the scene out by closing down gradually, wound the film back the same number of frames, and faded the next scene in over it. Georges Méliès was already joining the tableaux of his trick films this way around 1900. Later the work moved to the lab, where an optical printer rephotographed both shots onto one new strip of film. Because that strip was a generation further from the negative, the picture in many classic films turns softer and grainier a second before a dissolve begins, then snaps back to full quality after it ends. Digital editing ended that penalty, which is partly why dissolves are now so often overused.

Dissolve vs. fade: what's the difference?

A dissolve goes from one image straight into another. A fade goes through black (or white, or another color): the picture sinks to black, and the next scene rises out of it, a move editors call a dip to black when it happens mid-film.

The difference is punctuation. A cut is a comma, a dissolve a semicolon, a fade a full stop. Dissolve between two shots of the same afternoon and you have shown an hour passing; fade to black between them and you have ended a chapter, maybe a day. Fades open and close films and acts; dissolves connect scenes within them.

The midpoint of a dissolve can also look exactly like a superimposition or a double exposure, and people often mix them up. The test is time. A dissolve always resolves: the first image leaves and the second remains. A superimposition holds both images on screen as a composite for as long as the filmmaker wants, and a double exposure is recorded on the same frame in the camera, often with one image masked into a silhouette of the other.

Watch the midpoint of each clip and loop, where both images share the frame at half strength. Notice how the best ones place a face or a bright shape where the other image is dark or empty, so the blend stays readable.

Image and video models can do two things for a dissolve: generate the frames on both sides of it with matching compositions, and generate the blended midpoint as a mood frame or poster. In FlashBoards the outgoing frame, the incoming frame and the blend sit side by side on one board, so you can check that shapes line up before the edit.

Common mistakes

• A double exposure instead of a dissolve. Image models tend to mask one picture inside the silhouette of the other. Ask for a "uniform 50/50 blend across the whole frame" and give the face a plain, dark background.
• One image wins. If one layer comes out at full strength, say "both images equally transparent" and describe what shows through where.
• Morphing instead of blending. Video models often reshape the first subject into the second. Keep the incoming image made of things already in the frame, and use "transparent layers" and "cross-dissolve" rather than "transforms into".
• Drifting framing. For same-frame dissolves, generate both states from the same start frame and repeat "locked-off, same framing"; then do the blend in the edit, where you control its length to the frame.

Further reading

Walter Murch, In the Blink of an Eye (Silman-James Press, 2nd ed. 2001). Karel Reisz and Gavin Millar, The Technique of Film Editing (Focal Press). David Bordwell and Kristin Thompson, Film Art: An Introduction (McGraw-Hill).