Film specifications#
- Manufacturer
- 3M
- Film
- Color Slide 640-T
- Type
- Color slide film
- Speed
- 640
- Process
- E-6
- Formats
- 135
- Base
- Triacetate
- Made in
- Italy
- Status
- Discontinued — replaced by Scotch Chrome 640-T
Character & history#
High speed color reversal film for artificial light
Description adapted from Wikipedia’s “List of discontinued photographic films” (CC BY-SA 4.0).
Exposure guide at ISO 640#
Sunny 16 for this film: f/16 at 1/640 s in bright sun. Negative film tolerates 2–3 stops of overexposure; slide film needs accuracy within about ⅓–½ stop.
| Light | f/2 | f/4 | f/8 | f/16 |
|---|---|---|---|---|
| EV 16 · Snow / beach, bright sun | — | — | — | 1/1600 s |
| EV 15 · Bright sun | — | — | 1/3200 s | 1/800 s |
| EV 14 · Hazy sun | — | — | 1/1600 s | 1/400 s |
| EV 13 · Cloudy-bright | — | 1/3200 s | 1/800 s | 1/200 s |
| EV 12 · Overcast / open shade | — | 1/1600 s | 1/400 s | 1/100 s |
| EV 10 · Sunset | 1/1600 s | 1/400 s | 1/100 s | 1/25 s |
| EV 8 · Bright interior | 1/400 s | 1/100 s | 1/25 s | 1/6 s |
| EV 5 · Home interior at night | 1/50 s | 1/13 s | 0.3 s | 1.3 s |
| EV 3 · City street at night | 1/13 s | 0.3 s | 1.3 s | 5 s |
Long exposures#
Most films suffer reciprocity failure beyond about 1 second: they need more exposure than the meter says. As a rule of thumb add ⅓–1 stop for 1–10 s and 1–2 stops beyond 10 s for older emulsions; modern T-grain films (and Fuji Acros) need much less. Check the manufacturer's datasheet.
Similar films#
Other color slide film around ISO 640.
- 3M Scotch Chrome 640-T ISO 640 · disc.
- Imation Chrome 640T ISO 640 · disc.
- 3M Scotch Chrome 800/3200P ISO 800 · disc.
More 3M films#
Frequently asked questions#
What ISO is 3M Color Slide 640-T?
640 — set your meter to ISO 640 for box speed.
Is 3M Color Slide 640-T still made?
No, it has been discontinued (1982–?).
How do I develop 3M Color Slide 640-T?
E-6 process. Colour reversal (slide) chemistry. Fewer labs run E-6 today; it can be cross-processed in C-41 for saturated, contrasty colours.
Is 3M Color Slide 640-T available in 35mm?
Yes — formats: 135.
Sources & licences#
- Wikipedia: List of discontinued photographic films — CC BY-SA 4.0
Last updated October 03, 2026 · How we calculate · Sources