You get your scans back and one of your photos has a big orange streak running down the side. The next photo looks normal. A few frames later, there's another streak in almost exactly the same place. Congratulations, your camera may have accidentally discovered special effects.
Light leaks are one of the more recognizable problems in film photography. Sometimes they're subtle enough that people intentionally try to recreate the look. Other times they wash across half the photograph and destroy exactly the part of the frame you cared about.
The good news is that a light leak isn't random magic. If you look at the pattern across the roll and, ideally, the negatives themselves, you can often narrow down where the unwanted light is getting in.
What Is a Light Leak?
Your film camera is supposed to be light-tight.
When you're not taking a photograph, the only light reaching the film should be essentially none. When you press the shutter, the camera briefly allows a controlled amount of light through the lens and onto one frame of film. A light leak happens when light finds another way in.
Maybe the foam around the camera back has deteriorated. Maybe the hinge isn't sealing properly. A bellows camera could have a tiny pinhole. A damaged film door may not close tightly anymore. With 120 film, a loosely wound roll can sometimes allow light to reach the edges of the film.
Whatever the source, the result is the same: part of the film receives light that wasn't supposed to be there. Once that film is developed, the extra exposure becomes visible along with the photograph you actually intended to take.
What Do Light Leaks Look Like on Film?
There isn't one universal light-leak pattern. On color negative film, you might see a red or orange streak, a yellow glow, a pale or white band, or a large washed-out patch covering part of the photograph. Some leaks are soft and hazy. Others have surprisingly sharp edges.
The pattern is often more useful than the exact appearance. If the same orange streak appears along the same edge of five different photographs, that's telling you something. If only the first couple of frames are fogged, that's telling you something different.
And if the strange mark is visible in the scan but not on the physical negative, you're probably not looking at a camera light leak at all. Before trying to repair anything, start by looking for a pattern.
Look at the Negatives, Not Just the Scans
This is one of those situations where getting your negatives back is genuinely useful. A scan shows you the photograph inside the frame. The strip of film shows you what happened around it too.
Suppose a bright orange streak runs through your photograph and continues beyond the edge of the image into the space around the frame. The camera's lens didn't project an image there. That makes unwanted light reaching the film outside the normal exposure path a much stronger possibility.
You can also lay several frames beside one another and see whether the mark repeats in the same area of the film. If you're troubleshooting from scans alone, you're missing some of the best evidence.
This same principle is useful for plenty of other film problems. In our Why Did My Film Roll Come Back Blank? guide, we use the negatives and their edge markings to help distinguish between loading, exposure, camera, and processing problems.
Why Are Some Light Leaks Red or Orange?
If you're shooting color negative film, the color of a leak can sometimes help narrow down where the unwanted light reached the film.
A red or orange leak often means light reached the film from the back side and traveled through the film base before exposing the light-sensitive layers. That's why deteriorated seals around the camera back are such a common suspect when warm-colored leaks appear.
This isn't a rule we'd use by itself to diagnose a camera. The way film winds inside different cameras, the intensity of the leak, the film stock, and scanning can all affect what you see.
Still, if you have orange streaks appearing repeatedly near the same edge of your photographs and the foam around the camera back is crumbling into black goo, you have a pretty good place to begin looking.
What About White Light Leaks?
White or pale leaks can suggest that unwanted light reached the emulsion more directly rather than traveling through the back of the film first.
That can make the diagnosis a little more complicated. Possible sources include a problem around the lens or shutter, a crack in the camera body, damaged bellows, or another opening that allows light toward the front side of the film.
But don't replace your shutter because somebody on the internet told you "white means shutter." Color is just one clue that points towards the potential cause. The location of the mark, whether it repeats, whether it extends outside the image area, what kind of camera you're using, and what the negatives look like are all clues too. Use them together.
Why Don't Light Leaks Show Up on Every Photo?
This throws people off all the time. If the camera has a hole in it, shouldn't every frame have the same leak?
Not necessarily.
A tiny gap in a camera back may only allow significant light inside when bright sunlight hits it from a particular direction. One frame might sit behind that gap while you walk around outside for ten minutes. Another might only be there for a few seconds before you advance the film.
How long a frame sits in a particular position can matter too. Think about a manual-advance 35mm camera. After taking a picture, you might immediately advance to the next frame and then carry the camera around for an hour before taking another photograph. If a small leak exists near the camera back, that unexposed frame may spend much longer sitting near it than the previous frame did.
Change the angle of the sun, how long the film sits in the camera, or how the camera is being carried and the leak can change dramatically. An intermittent light leak doesn't rule out a bad seal.
The Most Common Culprit: Old Light Seals
If you're using a film camera that's 30, 40, or 50 years old, there's a good chance some of its original foam has had a harder life than you have.
Many cameras use foam or similar material around the film door, hinge, latch, or other openings to keep outside light from reaching the film, and unfortunately that material doesn't last forever.
Old foam can flatten, shrink, crumble, become sticky, or disappear almost entirely. Once that happens, the camera body may still look perfectly normal from the outside while a narrow path has opened for light to reach the film.
Open the camera back with no film loaded and inspect the channels around the door. Pay particular attention to the hinge and latch areas.
Healthy seals should actually fill the gap they're intended to seal. If you're seeing bare channels, chunks missing, sticky residue, or foam that turns to dust when touched, replacement is worth considering.
Other Places a Camera Can Leak
Bad door seals are common, but they're not the only possibility.
A warped or damaged film door may not sit tightly against the camera body even with good seals. Cracks or missing components can create another path for light. Cameras with interchangeable backs introduce additional mating surfaces that need to remain light-tight.
Shutters can create problems that resemble light leaks as well. A damaged shutter curtain or a shutter that isn't closing correctly can expose areas of the film that weren't supposed to receive light.
This is why replacing foam isn't a guaranteed cure for every mysterious streak. It's a sensible first place to look on many older cameras, but the evidence should guide the repair.
Can Loading Film in Bright Sun Cause a Light Leak?
It can cause unwanted fogging, although technically the camera itself may be perfectly light-tight once it's closed.
With 35mm film, the leader has to come out of the canister during loading. Some exposure at the beginning of the roll is expected, which is one reason cameras generally have you advance past the initially exposed section before starting your usable frames.
Loading or unloading in harsh direct sunlight can allow more stray light into exposed portions of the film than necessary. A simple habit helps: load and unload your camera in shade when possible. You don't need a darkroom. Just avoid holding an open camera and exposed film in direct midday sun if you have an easy alternative.
If fogging only appears near the beginning or end of one roll and never repeats on later rolls, handling becomes more plausible than a permanent leak in the camera.
Light Leaks on 120 Film Can Be Different
Medium-format roll film adds another variable: backing paper.
Unlike 35mm film sitting inside a metal canister, 120 film is wound together with opaque backing paper that protects it from light, and the roll needs to stay tightly wound.
If it becomes loose after shooting, light can work its way around the edges of the backing paper and fog the film underneath. Photographers often call this a fat roll because the finished roll is visibly looser or larger than it should be. This can produce edge fogging or irregular leaks even if the camera body itself is fine.
When shooting 120, keep the roll snug while loading and unloading it, wind it completely onto the take-up spool, and secure the finished roll promptly. If the problem only happened to one loosely wound roll, replacing your camera's seals probably isn't going to fix anything.
Could It Be Lens Flare Instead?
Absolutely.
Point a lens toward a strong light source and light can bounce between optical surfaces inside the lens. That can create haze, colored shapes, reduced contrast, or bright areas that look strange enough to be mistaken for a leak.
Lens flare comes through the lens as part of the optical exposure. A light leak reaches the film through a path that shouldn't be letting light into the camera at all.
Again, the negatives help.
If the effect is confined to the image area and only appears when a bright light source is in or near the frame, lens flare becomes a much stronger possibility. If the mark continues outside the image frame onto parts of the film that the lens couldn't expose, start looking somewhere else.
Could the Film Lab Have Caused It?
Unwanted light exposure can happen anywhere undeveloped film is exposed to light, including after it leaves the camera.
So yes, handling problems during processing are possible.
But the appearance of one unusual streak isn't enough to tell you when it happened.
A repeating mark in the same place across multiple rolls from the same camera points toward the camera. A problem limited to an outer portion of one roll may point toward loading, unloading, or another handling issue. If several unrelated rolls processed together showed an unusual common problem, the lab would have reason to investigate its side of the process.
At BG Film Lab, we'd rather look at the evidence than automatically blame either the photographer or the lab. Film problems are often surprisingly logical once you can inspect the negatives, frame sequence, edge areas, and pattern across the roll.
If you'd like a better understanding of when film remains light-sensitive during processing, our How Does Film Developing Work? guide walks through the process.
Can You Fix a Light Leak in the Scan?
Sometimes you can make the photograph look better. Whether that means the damage is truly "fixable" depends on how severe it is. A small leak in an unimportant corner may be easy to crop or retouch. A faint warm streak might even be something you decide to keep.
A heavy leak is different. Remember that the leak is an additional exposure recorded directly onto the film. If enough unwanted light hit an area, the original image information underneath it can be overwhelmed.
Editing software can change color, brightness, and contrast. It can't reconstruct a face or other detail that was completely obliterated by exposure. So if you like the effect, enjoy it. If you don't, preventing the next leak is much more effective than trying to repair every photograph afterward.
How Do I Find Where My Camera Is Leaking?
Don't start by replacing random parts, take a closer look at your camera and negatives and that should give you a good place to start.
Look at all of the affected frames together. Does the mark repeat in roughly the same place? Is it strongest on one edge? Does it extend outside the image area? Is it warm-colored or pale? Does it happen more often in bright sunlight? Did the problem appear on multiple rolls from the same camera?
Then inspect the obvious physical suspects with the camera unloaded.
Look at the foam around the film door. Check the hinge and latch. Make sure the back closes firmly and isn't visibly bent. If the camera has bellows, inspect them carefully. If it has interchangeable backs, inspect the surfaces where the pieces meet.
If the seals are visibly deteriorated, that's a reasonable repair to make regardless.
If everything looks healthy but the same problem keeps appearing across multiple rolls, it may be time for a closer mechanical inspection rather than continuing to sacrifice film to troubleshooting.
Does Your Camera Need New Light Seals?
If your camera's light seals are crumbling, sticky, flattened, or missing altogether, replacing them is often the next step. The good news is that this is a repair you don't necessarily have to tackle yourself.
BG Film Lab can replace deteriorated light seals on most film cameras. If you're seeing repeated light leaks and suspect the seals are the problem, you can bring or send the camera to us for inspection and service. You can learn more about our Camera Repair & Maintenance services.
Keep in mind that new light seals won't solve every light leak. If the seals still look healthy, or you've replaced them and the problem continues, there may be another path allowing light into the camera. That's when the pattern on your negatives and a closer inspection of the camera become especially useful.
A Simple Test Before You Trust the Camera Again
After making a repair, don't use your next roll for something irreplaceable, shoot a test roll first.
Use the camera in several lighting conditions, especially bright outdoor light where a small leak is more likely to reveal itself. Let a few frames sit in the camera for a while before advancing. Rotate the camera so sunlight hits different sides of the body.
You're not trying to make great photographs. You're trying to give a leak every opportunity to show itself. Once the roll is developed, compare the negatives with the previous problem roll.
If the repeated streak is gone, you've learned something useful. If it's still there, you've also learned something useful and can continue narrowing down the source. One boring test roll is cheaper than discovering the problem still exists halfway through a vacation.
Light Leaks Are Easier to Diagnose Than They First Appear
A strange red streak across your film can look completely random when you first see it. Usually though, it isn't.
The color can give you a clue. The position can give you another. The physical negative can show whether the unwanted exposure extends outside the image area. Repetition across several frames can point toward the camera, while a problem isolated to the beginning or end of a roll may send you looking at film handling instead.
Start with the evidence before you start replacing parts. And if you intentionally like the light-leak look, that's perfectly fine too. Plenty of photographers do.