An Exposure Value (EV) of 0 is defined as an exposure of 1s @ f/1.0 and ISO 100 (or any equivalent combination of exposure time, aperture and ISO).

When photographing natural scenes in very dim conditions (i.e., at night, away from artificial lights), the following exposure guidelines may come in handy:

- Clear sky, stars only (no moon): EV -7 (e.g., 30min @ f/4 and ISO 100)

(If the aim is to obtain STAR TRAILS, it will be necessary to aim for long exposure times, so that the trails come out nice and long, and not merely like 'blurred points'. In most cases, nice start trails require exposure times of at least 15 minutes.)

- Northern lights (weak): EV -6 (e.g., 30s @ f/2.8 and ISO 1600)

- Northern lights (strong): EV -4 (e.g., 15s @ f/2.8 and ISO 800)

- City lights & neon signs: EV 4 (e.g. 1/30s @ f/2.8 and ISO 1600)

- Fireworks: f/8 and ISO 100 (exposure time does not matter: use Bulb setting and multiple exposure mode to capture more fireworks in one frame)


N.B.: If shooting with film, make sure to increase these exposure times further to compensate for reciprocity failure, as appropriate - see tables below for four popular colour film stocks. E.g.:
- with Kodak Ektachrome E100, EV-7 would be 30min @ f/4, but the actual exposure time should be 50min @ f/4 to account for reciprocity failure.
- with Kodak Ektar 100, EV-6 would be 8min @ f/2.8, but the actual exposure time should be 22min @ f/2.8 to account for reciprocity failure.

Fujichrome Velvia 50 reciprocity chart (Tc = Tm^1.2):

Read

1s

2s

4s

8s

15s

30s

1m

2m

4m

8m

15m

30m

Use

1s

2s

5s

12s

28s

64s

2m 30s

6m

13m

30m

1h 10m

2h 40m

 

Kodak Ektachrome E100 reciprocity chart (Tc = Tm^1.05):

Read

1s

2s

4s

8s

15s

30s

1m

2m

4m

8m

15m

30m

Use

1s

2s

4s

8s

18s

38s

1m 20s

3m

6m

12m

24m

50m

 

Kodak Ektar 100 reciprocity chart (Tc = Tm^1.15):

Read

1s

2s

4s

8s

15s

30s

1m

2m

4m

8m

15m

30m

Use

1s

2s

5s

11s

24s

54s

2m

4m

10m

22m

48m

1h 50m

 

Kodak Portra 400 reciprocity chart (Tc = Tm^1.33) :

Read

1s

2s

4s

8s

15s

30s

1m

2m

4m

8m

15m

30m

Use

1s

2.5s

6s

16s

40s

1m 40s

4m

11m

27m

1h

3h

7h