C-41 colour film development

This guide covers the step-by-step process of developing C-41 film. The process consists of three main stages: developing, bleaching, and fixing.

1. Develop

The first step is to develop the film, turning the latent image into a visible negative.

As with black & white film, this is done by converting the exposed silver halide crystals into metallic silver. The metallic silver absorbs light and appears black, creating a negative of the light areas of the scene.

Light exposure & density

• Areas that received more light become denser with metallic silver.
• Areas that received no light remain as silver halides, which will be removed later.

Unlike black & white film, C-41 developer also contains dye couplers which forms a colour dye around each of the metallic silver grains. The colour of this dye is the opposite of the colour of light that exposed the film.

Colour negatives

• Areas that received red light form cyan dye
• Areas that received green light form magenta dye
• Areas that received blue light form yellow dye

Through the combination of cyan, magenta and yellow dyes the colours and contrast of the image are formed.

Note:

While most film produces a colour negative when developed using the C-41 process, there are some notable exceptions. Ilford's XP2 film is developed using the C-41 process, but produces a black & white negative.

Development time & temperature

• Standard time: 3 minutes 15 seconds
• Required temperature: 38°C (100.4°F) ± 0.3°C
• Any variation in temperature or time can cause colour shifts

To prevent colour shifts, use a temperature-controlled water bath for the most consistent results. These can be made at home using a large sink basin, and a sous vide immersion circulator.

Agitation technique

Regular agitation ensures even development by moving fresh chemistry over the film surface.

Standard tank method:

• Invert the tank for 15 seconds every minute.
• No adjustment to development time is needed.

Rotary processors:

• Agitation speeds up development and can lead to increased contrast if excessive.
• When using continuous rotary processors, reduce development time by 15%.

2. Bleach

After development, the bleach converts metallic silver back into silver halides, allowing it to be removed in the fixing stage. This leaves only the colour dye clouds formed during development, giving the negative a bright and saturated appearance. Skipping the bleach step is a technique commonly referred to as bleach bypass.

Bleach time & temperature

• Standard time: 6 minutes
• Temperature: Not as critical, but keeping it close to 38°C is ideal
• Agitation: Continuous or 10 seconds every 30 seconds

Bleach & fix combined

Some C-41 film developing kits come with a combined bleach and fix step, often labeled 'Blix'. Wherever possible, you should follow the instructions provided by the manufacturer.

3. Fix

Fixing removes unexposed silver halide crystals from the film, making the negative stable and light-safe. If the film is exposed to light before being fixed, the remaining silver halides will become exposed. This appears as a cloudy fog in the clear areas of the negative.

Fix time & temperature

• Standard time: 6 minutes seconds
• Temperature: Not as critical, but keeping it close to 38°C is ideal
• Agitation: Continuous or 10 seconds every 30 seconds

If fogging appears after fixing, the negatives can be re-fixed to clear the remaining halides. Colour negative film can appear slightly foggy when wet, so drying the film before deciding to re-fix might prevent doing so unnecessarily.

4. Stabiliser

The stabiliser prevents colour shifts and fading over time. It contains chemicals that protect the dyes in the emulsion.

Stabiliser time & temperature

• Standard time: 1 minute
• Temperature: Not as critical, but keeping it close to 38°C is ideal
• Agitation: Continuous or 10 seconds every 30 seconds