E-6 Processing: How Slide Film Is Developed

E-6 is the process that turns color slide film into positive transparencies. It has more steps than C-41 and is less forgiving of temperature errors, because it develops the image twice: once as a negative, and once more as a positive. Fewer labs run it than C-41, but it can be done at home with a kit.

How reversal processing works

Slide film is exposed like any other film, forming a latent image. The trick of E-6 is that it develops that image and then throws it away:

The first developer, a black and white developer, turns exposed crystals into a silver negative image. No color forms yet.
The reversal step fogs all the remaining, unexposed crystals, chemically in modern E-6 (older processes used a light exposure).
The color developer develops those remaining crystals, forming silver plus dyes. Because they are the areas that originally received little light, the dye image is a positive.
A bleach and fixer remove all silver, both the first negative and the second, leaving only the positive dye image.

Because the first developer decides how much halide remains for the color image, it controls the slide's overall density. It is the most critical step.

The E-6 steps

Step	Purpose
First developer	Forms the black and white negative image; sets density
Wash	Stops first development
Reversal bath	Fogs remaining halide (combined with color developer in some kits)
Color developer	Develops the remaining halide with dyes to form the positive
Pre-bleach or conditioner	Prepares the film for bleaching
Bleach	Converts silver back to halide
Fixer	Removes all halide
Wash and final rinse	Removes chemicals, stabilizes dyes

Home kits often combine steps, for example a three-bath kit with first developer, color developer and blix. They are simpler but may not match a lab's six-bath results exactly.

Temperature

E-6 runs at 100°F (38°C). The first developer tolerance in the professional process is about half a degree Fahrenheit (0.3°C). An error of a degree or two in the first developer changes the density of every slide on the roll. Use a reliable water bath and check the temperature of the chemistry, not just the bath.

Pushing and pulling slide film

Extending the first developer time pushes slide film; shortening it pulls. Because the first developer controls density directly, E-6 pushes cleanly, typically with around 30 to 40 percent more first developer time per stop. Pushed slides have more contrast and slightly shifted color. See push and pull processing.

Exposing slide film well

E-6 can't save a badly exposed slide. Meter for the highlights, avoid scenes with a contrast range much over five stops, and bracket when you can. Exposure latitude explains why slide film is so exacting.

Viewing, scanning and storing slides

Slides can be mounted in frames for projection and light box viewing, or left in strips in sleeves. They scan beautifully because the image is already positive and there is no orange mask to remove. Store them away from light: dyes fade with exposure, and Ektachrome and Fuji slide films are more stable in the dark than on display. See how to scan film.

Current E-6 films

Slide films still made include Kodak Ektachrome E100, Fujichrome Velvia 50 and Velvia 100, and Provia 100F. Old slide films that used other processes, such as Kodachrome's K-14, can only be developed as black and white today.