Agitate › C-41 timer
Color negative at home
C-41 Timer for Developing Color Film at Home
Six C-41 kits are built into Agitate, each written out bath by bath from the instruction sheet that came with it. The app times each one at the temperature its maker published, and it will not convert that temperature to another.
- Developer
- Bleach
- Wash
- Fixer
- Wash
- Stabilizer
Six kits, and they are not interchangeable
The single most repeated number about C-41 is 3 minutes 15 seconds at 38 degrees. It is a good average and it is wrong for two of the six kits in the app. Kodak publishes its Flexicolor developer at 37.8 degrees, CineStill publishes Cs41 at 39, and Arista publishes at 38.9. The bleach step ranges from under a minute to six and a half. Some kits bleach and fix separately, some use a single blix.
| Kit | Developer | Temperature | Baths |
|---|---|---|---|
| Kodak Flexicolor | 3:15 | 37.8 °C | 6 |
| Bellini | 3:15 | 38.0 °C | 5 |
| Tetenal Colortec | 3:15 | 38.0 °C | 5 |
| Rollei Colorchem | 3:15 | 38.0 °C | 5 |
| Arista | 3:30 | 38.9 °C | 5 |
| CineStill Cs41 | 3:30 | 39.0 °C | 5 |
Transcribed from each maker's own instruction sheet. Every template in the app names the document it came from.
Pick your kit and the whole sequence comes with it, including the two details people improvise: which baths carry on at process temperature, and which ones drop to room temperature. In the CineStill and Arista templates the stabilizer is published at 20 degrees, and in the Rollei template at 22.5. That is what the app times.
The app refuses to compensate a C-41 time
Time and temperature conversion is a black and white technique. In a color process a deviation is not a density error you can develop your way out of, it is a shift in color balance, and no manufacturer publishes a conversion rule of that form for C-41. An app that hands you a confident compensated number there is not being precise, it is being wrong in a way you only find out at the scanner.
So Agitate declines. What it does instead is warn: the published tolerance it holds you to for C-41 is 0.15 degrees, tighter than the 0.5 degrees it allows for black and white, and a measurement outside that band is called before you pour rather than after. More on how the conversion works, and where it stops.
Three and a quarter minutes is where a timer earns its place
A C-41 developer runs for about three minutes at close to 38 degrees, inside a water bath, usually with wet hands and a tank you cannot put down. Three things in Agitate are built for exactly that.
The drain is called
Ten seconds before time on every bath with a pour, because the published time includes the pour out. A timer that rings at 3:15 gives the developer 3:15 plus however long your drain takes, on every roll.
Nothing can freeze it
The app stores the moment the bath ends, not the seconds left in it. A call in the middle of the developer does not cost you the roll, and neither does the app being force quit.
The whole screen is the button
Next bath is the entire display. You do not aim for a small control with a wet hand while a tank drains into the sink.
The one warning that does not apply here is the short development warning. C-41 develops for around three minutes by design, so Agitate keeps the under five minutes caution to black and white, where it belongs. An app that warned about every correctly configured color run would be teaching you to ignore it.
Pushing C-41
In C-41 a push is done by extending the developer and nothing else. Bleach, blix, fix, wash and stabilizer keep the time the kit published. Agitate applies the change to the developer alone, and where no published row covers the exposure index you asked for, the number it derives is labeled as an estimate rather than dressed up as a manufacturer figure. How push and pull times are worked out.
Re-use is handled the same way. The ten percent per film surcharge for re-used developer is a black and white convention, and stretching a color developer that way shifts color balance rather than adding density. Agitate does not apply it to C-41. Expiry and exhausted capacity are still called: an exhausted kit is exhausted whatever the process.
C-41 at home, timed off the sheet that came with your kit
Six kits, bath by bath, with the drain called and the clock running through a locked phone. Black and white and E-6 are in the same app.
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