The Rollei Ortho 25 is a black and white film. It is a steeply working B/W film. The sensitivity of the orthochromatic film is given as ISO 25.
The processing of the Rollei Ortho 25 takes place in a suitable black and white developer. Different developers can be used for this purpose. Depending on the developer and exposure, the results can vary.
Development Times
| Developer | Dilution | ISO | Time | Temperature |
|---|---|---|---|---|
| Rodinal | 1+25 | ISO 25 | 4 min | 20 °C |
| Rodinal | 1+50 | ISO 25 | 6 min | 20 °C |
Calculation of the development solution
| Dilution | Developer (ml) | Water (ml) |
|---|---|---|
| 1+25 | 19 | 481 |
| 1+50 | 10 | 490 |
Film Formats
It is available in a wide range of formats. It is available for 35mm cameras (135-36, bulk), medium format cameras (120, 70mm bulk), and large format cameras (2.25x3.25", 4x5", 5x7", 8x10", 12x16").
What is an orthochromatic film?
Orthochromatic film is a photographic film that has a particular sensitivity to certain colors or wavelengths of light. It is sensitive to blue and green light, but insensitive to red and yellow light, creating stark contrasts when these colors are present in the scene.
The term "orthochromatic" means "correct color", but it is important to note that this does not mean that the film can accurately reproduce all colors, as its insensitivity to red light leads to different interpretations of scenes, especially in portraits, where skin tones can appear much darker.
Its unique light sensitivity was standard in early photography, but with the advent of panchromatic film, which is sensitive to all visible colors of light, orthochromatic film is now mainly used for special artistic and technical applications.
Example Photos
The pictures were taken with the Olympus OM 2 and an expired Rollei Ortho 25. The black and white film was developed in Rodinal and digitized with a Canoscan 9000F flatbed scanner (eBay / Amazon*).
