Film specifications#
- Manufacturer
- Agfa
- Film
- Agfacolor/Agfachrome CT21
- Type
- Color slide film
- Speed
- 100
- Process
- AP 41
- Formats
- 135
- Base
- Triacetate
- Made in
- Germany
- Status
- Discontinued — replaced by Agfachrome CT 100
Character & history#
General purpose color reversal film, similar to CT18 but with speed of ISO 100/21°. Renamed to Agfachrome in 1978.
Description adapted from Wikipedia’s “List of discontinued photographic films” (CC BY-SA 4.0).
Exposure guide at ISO 100#
Sunny 16 for this film: f/16 at 1/100 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 | — | — | 1/1000 s | 1/250 s |
| EV 15 · Bright sun | — | 1/2000 s | 1/500 s | 1/125 s |
| EV 14 · Hazy sun | — | 1/1000 s | 1/250 s | 1/60 s |
| EV 13 · Cloudy-bright | 1/2000 s | 1/500 s | 1/125 s | 1/30 s |
| EV 12 · Overcast / open shade | 1/1000 s | 1/250 s | 1/60 s | 1/15 s |
| EV 10 · Sunset | 1/250 s | 1/60 s | 1/15 s | 1/4 s |
| EV 8 · Bright interior | 1/60 s | 1/15 s | 1/4 s | 1 s |
| EV 5 · Home interior at night | 1/8 s | 0.5 s | 2 s | 8 s |
| EV 3 · City street at night | 0.5 s | 2 s | 8 s | 30 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 100.
- Flic Film Chrome ISO 100
- Fujifilm Fujichrome Provia 100F ISO 100
- Fujifilm Fujichrome Velvia 100 ISO 100
- Ilford Ilfochrome 100 ISO 100
- Kodak Ektachrome E100 ISO 100
- Rera Chrome 100 ISO 100
- 3M Color Slide 100 ISO 100 · disc.
- 3M Scotch Chrome 100 ISO 100 · disc.
- Agfa Agfachrome 100 RS ISO 100 · disc.
- Agfa Agfachrome CT 100 ISO 100 · disc.
- Agfa Agfachrome CT 100i ISO 100 · disc.
- Agfa Agfachrome CT 100x ISO 100 · disc.
- Agfa Agfachrome R100S Professional ISO 100 · disc.
- Agfa Agfachrome RSX 100 ISO 100 · disc.
- Agfa Agfachrome RSX II 100 ISO 100 · disc.
- Agfa CTprecisa 100 ISO 100 · disc.
- AgfaPhoto CTprecisa 100 ISO 100 · disc.
- AgfaPhoto CTprecisa 100 (new) ISO 100 · disc.
More Agfa films#
Frequently asked questions#
What ISO is Agfa Agfacolor/Agfachrome CT21?
100 — set your meter to ISO 100 for box speed.
Is Agfa Agfacolor/Agfachrome CT21 still made?
No, it has been discontinued (1974–1984).
How do I develop Agfa Agfacolor/Agfachrome CT21?
AP 41 process.
Is Agfa Agfacolor/Agfachrome CT21 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