Common Film Problems: Light Leaks, Thin Negatives, Fogging and Scratches

When a roll comes back wrong, the negatives usually tell you why. A film's edge markings, the spaces between frames and the pattern of the fault point to whether the problem happened in the camera, during exposure or in development. Here is how to read the clues for the most common film problems.

Start with the edge markings

Film is printed at the factory with a latent image along its edges: frame numbers and the film name. These develop along with your pictures, so they are a built-in test of development.

Edge markings visible, frames blank: development was fine; the film was never exposed.
Edge markings missing and the film completely clear: it was not developed. Usually fixer was poured in first, or the developer was dead.
Film completely black or dark: exposed to light before development, such as opening the camera back or tank.

Blank rolls

Clear film with visible edge printing usually means the film never advanced: the leader slipped off the take-up spool. It can also mean a shutter that never opened, or a lens cap left on a rangefinder. Check that the rewind knob turns as you advance. See how to load film.

Thin negatives

A thin negative has too little density: it looks pale and prints dark and murky. Two causes, with different signs:

Underexposure: shadows are empty, but highlights and edge markings have normal density. Check the meter, the film speed setting and the shutter.
Underdevelopment: everything is weak, including the edge markings. Check developer dilution, temperature, time and age.

Dense negatives

Dense, dark negatives come from overexposure or overdevelopment. Overexposed negatives have good contrast and normal edge markings; overdeveloped ones have high contrast, dense edge markings and blocked highlights. Overexposed negatives are usually printable, just slower to print or scan.

Light leaks

Light leaks show as streaks, flares or patches of density, often orange or red on color negative and dark on black and white negatives.

Same place on every frame: a leak in the camera body, usually worn seals around the back hinge or door.
Extending between frames and into the edges: light got in while the film was outside the camera, such as a loose 120 roll or a cassette left in sun.
Only the first few frames: loading in bright light.

Buying a used film camera explains how to check seals.

Fog

General fog makes negatives gray all over, including between frames and in unexposed edges. Causes include expired or heat-damaged film, X-ray exposure, too much light while loading a developing reel, or a developer that is too warm or too long. Expired film almost always has some fog.

Scratches

Fine straight lines running the length of the roll are scratches from grit in the camera, the cassette's felt lips, or careless handling. If they appear in the emulsion on every frame, check the film rails and pressure plate. If they are on the base side, they often came from the cassette or the reel. Scratches on the base can sometimes be hidden in scanning with a little lens-cleaning oil or a wet scan.

Development faults

Problem	Looks like	Cause
Uneven development	Streaks, mottling, uneven sky	Too little agitation, not enough developer, film not fully covered
Surge marks	Dense streaks from sprocket holes	Overly vigorous agitation
Bromide drag	Light streaks below dense areas	Too little agitation; common in stand development
Kinks or crescents	Small dark or light crescent shapes	Film bent while loading the reel
Stuck frames	Undeveloped patches	Film layers touching on the reel
Air bells	Small round light spots	Bubbles; tap the tank after pouring
Reticulation	Crazed, cracked texture	Sudden large temperature change between baths
Drying marks	Spots and streaks	Hard water; use wetting agent or a distilled water final rinse
Milky or purple tint	Cloudy negatives	Underfixed; refix in fresh fixer

Overlapping and uneven spacing

Frames that overlap, or have uneven gaps, point to a worn film advance or a 120 back set to the wrong format. Half-exposed frames, with one side dark, suggest a sticking focal plane shutter curtain. Both need a repair technician; find one in the camera repair directory.

Still stuck?

Post a photo of your negatives held up to a light in The Darkroom, FilmPhotography.com's message board, and other members can help diagnose the problem.