Yes—film can be exposed for much longer than 2 minutes, even for many minutes or hours, but you must account for reciprocity failure. With long film exposures, exposure does not increase linearly, so simply doubling the time may not equal one extra stop.

For Ilford films, the best starting point is Ilford’s own reciprocity compensation data, which provides guidance by film type. There isn’t one universal formula that works for all films and all situations, because reciprocity behavior varies with the specific emulsion and can also be influenced by factors such as exposure time, light spectrum, and shooting conditions.

In practice:

• Use Ilford’s reciprocity chart/data for your exact film.
• Treat it as an estimate, not a guarantee.
• Bracket exposures when possible, especially for important shots.
• Test your film in your real shooting conditions if you need repeatable results.

For very long exposures such as star trails, film is typically exposed in a single long exposure rather than stacked like digital images. If you shoot color film, be aware that color shifts can also occur during long exposures.