What is a light leak in photography?

What exactly is a light leak?

Film is made to react to light, and a camera is supposed to keep every bit of it out except what comes through the lens. When light sneaks in through a worn seal, a loose back or a cracked cassette, it exposes part of the film. The result is a patch of color, usually red, orange or yellow, along an edge or across a corner. Wikipedia has a short entry on the light leak.

Because the leak hits the film itself, it shows up on the picture as part of the scene.

What causes light leaks on film?

• Foam light seals around the camera back that have crumbled with age.
• A back that was opened or not closed fully before the roll was finished.
• Cracks or gaps in a plastic body, common on cheap and old cameras.
• A damaged film cassette that lets light in at the slot.
• Loading or unloading in bright light.

What color is a light leak?

Warm colors are the ones people usually see: red, orange and yellow. The exact color depends on the film, the light and how long the leak lasted, so it can range from a faint haze to a bright flare.

Because the leak is random, no two are alike. That unpredictability is part of why people like it.

Why do photographers like them?

A leak breaks the clinical perfection of a modern picture. It adds warmth, hints at memory and gives a frame a trace of the process that made it. It is the visual equivalent of a crackle on a record. People started collecting leaky cameras on purpose, and designers began to imitate the look in software.

A caution is worth adding: leaks are rarely good on a picture you cannot repeat. A wedding or birthday frame ruined by a leak is a loss, and that is why labs and photographers fix seals on working cameras.

How do camera apps imitate a leak?

They draw a soft color glow over the frame, usually near an edge, with some variation from picture to picture. Good ones randomize position and strength so that two frames do not carry the same stamp. Weak ones paste the same overlay on everything, and you notice by the third shot.

In Proofsheet, light leaks are soft color glows over the frame, and they are a switch in the roll setup. The glow is applied when the roll develops, along with the film look you chose, so the viewfinder shows the plain scene. See film looks.

Do leaks work with every look?

They sit on top of the look. A warm look and a warm leak can stack into something heavy, so a cool or black-and-white look often pairs better with a leak than a golden-hour look does. Try a short 12-frame roll with leaks and another without them, then compare the sheets. The look is chosen when you load the roll, and you cannot change it afterward.

Can I get a real light leak on purpose?

You can, but it is unpredictable and can ruin a roll. Experimenters loosen light seals, leave a camera back slightly open or use a deliberately leaky plastic camera. It is a fun experiment with a cheap roll and a disposable approach to the outcome. If you want the effect with no risk, a digital version is safer.

For the broader story of how film errors became styles, see what is analog photography.

Is a digital leak the same thing?

No. It looks similar, but it is a designed glow, not an accident. That is not a flaw. A digital leak is controllable, repeatable and optional, and it comes with no risk to the frame underneath. Proofsheet is not on the App Store yet. When it is, leaks are one of the switches you choose when you load a roll.

How can I tell a leak from a flare?

A lens flare comes through the lens and looks like streaks or rings that follow the light source in the scene. A light leak comes from outside the lens and usually sits along an edge or corner, with no link to anything in the picture. If the glow ignores the scene, it is a leak.

Will it appear on every frame?

On real film, a leak can hit a few frames or the whole roll. In a camera app it depends on the setting. In Proofsheet the switch applies to the roll, and the glow varies from frame to frame, so you get a family of similar but different frames. Check the sheet for how consistent it feels.

How do I fix a leaky camera?

Replace the foam seals. Old cameras rely on foam strips in the back door, and they crumble with age. Replacement kits and tutorials exist, and a repair shop can do it quickly. Electrical tape on the cracks of a plastic body works as a stop-gap. If the leak is from the cassette, switch to a fresh roll.