# Shooting Expired Film

As photographic film ages it degrades. In simplistic terms, the film’s apparent sensitivity to light decreases over time. Theoretically, the degradation starts to becomes evident after the expiration date set by the manufacturer. So, it would be nice if there was a formula which could prescribe the proper compensation required for any roll of expired film. I naïvely started to work out a formula, but having limited data points, the task was futile. Instead, I decided to compile results based upon a system of rules of thumb, which are listed below.

After sharing my findings here, others have in turn shared their findings with me. With permission of the inventors, I am re-sharing their techniques, and any data they were able to provide. If you have a technique that isn’t already covered and would like to share it, then send me an email at fogged.film@christopherstoll.org and I will add it to the list.

## My Technique

For each film I would guess at a rule for how many years it would take for that type of film’s performance to degrade one stop. In the formula that rule will be called the degradation factor, or simply the factor. Then, I would calculate the age of the film in years. Finally, simply divide the age by the factor. The result is the number of stops to decrease the expired film’s speed by.

The formula is: `((YYYY + NN/12)-(ZZZZ + MM/12))/FACTOR`, where:

• `YYYY` is the current year
• `NN` is the current month
• `ZZZZ` is the year the film expired
• `MM` is the month the film expired
• `FACTOR` is the number of years needed to drop 1 stop (e.g. 1 stop / 25 years => FACTOR = 25).

For a film with a factor of 30, which expired 10/1998 and is to be shot 7/2023, the formula would be `((2023 + 7/12) - (1998 + 10/12)) / 30`. The result of that calculation would be `0.825`. In this case I would round down from 4/5 of a stop to 2/3 of a stop, though using a full stop could also make sense.

These rules of thumb apply to film with an unknown storage history, and assumes the film was probably not stored properly. They will be be updated as new data points are recorded.

### Black and White

#### Kodak T-MAX 100

Rule of thumb: 1 stop / 30 years

• Expired 1998-10, shot 2023-07 — ⅔ stops (EI 64) recommended

#### Ilford FP4 125

Rule of thumb: 1 stop / 25 years

#### Kodak Plus-X pan 125 (PXP)

Rule of thumb: 1 stop / 25 years

#### Kodak Verichrome pan 125 (VP)

Rule of thumb: 1 stop / 25 years

#### Kodak Tri-X pan 400 (TX)

Rule of thumb: 1 stop / 20 years

### Color

#### Kodak Ektar 25 (PHR)

Rule of thumb: 1 stop / 20 years

#### Kodak Kodacolor II 100

Rule of thumb: 1 stop / 15 years

#### Kodak Kodacolor VR-G 100 (CA 120)

Rule of thumb: 1 stop / 20 years

• Expired 1988-04, shot 2023-07 — 1¾ stops (EI 25) recommended

#### Kodak Vericolor III 160 (VPS)

Rule of thumb: 1 stop / 15 years

#### Fujicolor Super HQ 200

Rule of thumb: 1 stop / 14 years

#### Kodak Vericolor 400 (VPH)

Rule of thumb: 1 stop / 8 years

## Other People’s Techniques

### Greg Christie

Some approximations for B&W film:

• ASA/ISO 50 — one extra stop per 40 years
• ASA/ISO 100 — one extra stop per 20 years
• ASA/ISO 400 — one extra stop per 10 years
• Panatomic-X — no compensation because it’s a miracle film.

#### Examples

The following examples were shot in the last 2 years (2021-2023).

• AgfaPhoto APX100, expired 2009 — EI 50
• Efke KB25, expired 2013 — EI 20
• Efke KB100, expired 2012 — EI 25
• Efke KB100, expired 2012 — EI 32
• Efke R50, expired 2013 — EI 16
• Efke R50, expired 2013 — EI 20
• Kodak Panatomic-X (FXP120), expired 1989 — EI 32
• Kodak Tri-X pan 400 (TX120), expired 2004 — EI 160, 6½ minutes in HC-110 Dilution B (1+31) @ 68℉
• Kodak Verichrome Pan (VP120), expired 1989 — EI 50
• Kodak Verichrome Pan (VP127), expired 1966 — EI 25
• Kodak Verichrome Pan (VP620), expired 1964 — EI 25
• ReraPan 127, expired 2014 — EI 64