Film and darkroom, in plain words.

#

• 120 film Medium-format roll film, wound with a paper backing on a spool.
• 135 film The 35 mm film that comes in a metal cartridge, with sprocket holes along its edges.

A

• Acutance How sharp the edges in a picture look.
• Agitation Moving the developer over the film so that fresh solution reaches the emulsion.

B

• Black-and-white film Film that records only brightness, giving a negative in shades of grey made of metallic silver.
• Bleach In colour processing, the bath that turns the developed silver back into silver halide so that the fixer can remove it.
• Blix (bleach-fix) A single bath that bleaches and fixes colour film in one step.
• Box speed The ISO speed the maker prints on the box and the datasheet.
• Bracketing Taking extra frames of the same scene at slightly more and slightly less exposure than the meter suggests.

C

• C-41 The standard process for developing colour negative film.
• Changing bag A light-tight bag with sleeves, in which film is loaded onto a reel without a darkroom.
• Characteristic curve (H&D curve) A graph of the density a film gives against the exposure it received.
• Clearing time The time a film takes in fixer to lose its milky look and turn clear.
• Compensating developer A developer formulated to hold back the highlights while the shadows continue to develop.
• Contact sheet A print of a whole roll’s frames at their original size, made by laying the negatives directly on a sheet of paper.
• Contrast index A measure of the contrast of a developed film, taken from its characteristic curve.
• Cross processing Developing a film in a process it was not made for, such as slide film in C-41.

D

• Darkroom A room that can be made dark, for loading film and making prints.
• Dense negative A negative that is dark overall, with a lot of silver.
• Density How much light a negative, transparency or print blocks.
• Developer The solution that turns the exposed silver halide crystals in the film into visible metallic silver.
• Development tank The light-tight container in which film is developed.
• Development time How long the film stays in the developer.
• Dilution notation (1+1, 1:1) How the mix of concentrate and water is written: “1+1” means one part concentrate plus one part water.
• Dodging and burning Holding back light from part of a print (dodging) or giving it extra light (burning in) while exposing it.
• DX code A coding system on 35 mm film cartridges and film edges that lets cameras and processing machines identify the film.

E

• E-6 The standard process for developing colour slide (reversal) film.
• ECN-2 The process used for motion-picture colour negative film.
• Edge markings The names, numbers and codes exposed along the edges of a film and visible after development.
• Emulsion The light-sensitive layer of a film: tiny crystals of silver halide held in gelatin.
• Enlarger A projector that casts the image of a negative onto photographic paper, larger than the negative.
• Exposure index (EI) The speed you actually set on the meter or camera, which may differ from the film’s box speed.
• Exposure latitude How far a film can be over- or underexposed and still give a usable result.

F

• Film base The clear, flexible support that carries the emulsion.
• Fixer The chemical that dissolves the silver halide that was not developed and makes the image permanent.
• Fog Unwanted density in a negative or print that does not belong to the image.

G

• Gamma The slope of the straight-line part of a film’s characteristic curve, a measure of contrast.
• Grain The visible, sand-like texture in a photograph that comes from the clumps of silver or dye that form the image.

H

• Halation A glow around bright highlights, caused by light passing through the emulsion and bouncing back off the base or the camera back.
• Hypo clearing agent A solution that helps remove fixer from film or paper so that washing takes less time and water.

I

• Inversion Agitating a tank by turning it upside down and back again.
• ISO (film speed) A number that says how sensitive a film is to light: the higher it is, the less light the film needs.

K

• Kit A packaged set of the solutions for one process, such as C-41 or E-6.

L

• Latent image The invisible image that exposure leaves in the emulsion until it is developed.
• Light meter An instrument, built into the camera or separate, that measures light to suggest an exposure.

M

• Monobath A single solution that develops and fixes in one step.

O

• One-shot A developer used once and then thrown away.
• Orthochromatic Sensitive to blue and green light but not to red.
• Overexposure Giving the film more light than it needs for the result you want.

P

• Panchromatic Sensitive to all visible colours of light, including red.
• Pre-soak A rinse of plain water before the developer.
• Pull processing Rating a film slower than its box speed and developing it for less time.
• Push processing Rating a film faster than its box speed and developing it for longer to make up for the underexposure.

R

• Reciprocity failure The loss of a film’s effective sensitivity in very long (or very short) exposures, so that more exposure than the meter says is needed.
• Reel The spiral holder that keeps the turns of film apart inside the tank.
• Rem-jet A dark, carbon-based backing on motion-picture film that must be removed in processing.
• Replenishment Adding fresh developer, or a replenisher, to a developer in repeated use to keep its strength.
• Respool A film sold under one name made from another maker’s film, rewound onto new spools or cartridges.
• Reversal (slide) film Film that is processed to give a positive image on the film itself instead of a negative.
• Rotary processing Developing with a tank that is turned continuously, usually on a motorised base.

S

• Safelight A dim light of a colour that does not affect the photographic paper or film being handled.
• Silver halide The light-sensitive silver compounds in a film or paper emulsion, in the form of tiny crystals.
• Spectral sensitivity Which colours of light a film responds to, and how strongly.
• Split-grade printing Making a print in two exposures on variable-contrast paper, one with a soft filter and one with a hard filter.
• Stabiliser The last bath in some colour processes, which helps keep the dyes and avoids water marks.
• Stand development Developing in a very dilute developer for a long time with little or no agitation.
• Stock solution The concentrated form of a chemical, or a developer used undiluted.
• Stop A doubling or halving of the amount of light.
• Stop bath A weak acid bath that stops development after the developer.

T

• T-grain (tabular grain) A film emulsion made with flat, tablet-shaped silver halide crystals instead of the traditional rounder ones.
• Temperature compensation Changing the development time to suit a developer that is warmer or cooler than the temperature the time was published for.
• Test strip A strip of paper exposed in steps, to find the best exposure time for a print.
• Thin negative A pale negative with little density, in which the shadows are weak.

U

• Underexposure Giving the film less light than it needs.

V

• Variable-contrast paper Black-and-white paper whose contrast depends on the colour of the light used to expose it.

W

• Washing Rinsing the processed film in clean running or changing water to remove the processing chemicals.
• Wetting agent A few drops of a surfactant in the final rinse so that water drains evenly off the film.
• Working solution The chemical made up to the strength at which it is used.

Z

• Zone System A method of controlling exposure and development, devised by Ansel Adams and Fred Archer, that divides the tones of a scene into zones.