Reciprocity
Ilford Delta 3200 Professional long exposures
What a metered time becomes on Delta 3200 Professional, and the stops it adds — worked out from Ilford’s own data, never past it.
Your metered time
Tc = Tm^P for metered times over 1 s; 1 s or less needs no correction (P = 1.33)
At a glance
| Metered | Expose for | Added |
|---|---|---|
| 1 s | 1 s | — |
| 2 s | 2.5 s | +0.3 stops |
| 4 s | 6.3 s | +0.7 stops |
| 8 s | 16 s | +1 stops |
| 15 s | 37 s | +1.3 stops |
| 30 s | 1 min 32 s | +1.6 stops |
| 1 min | 3 min 52 s | +1.9 stops |
| 2 min | 9 min 43 s | +2.3 stops |
| 4 min | 24 min 24 s | +2.6 stops |
| 8 min | 1 h 01 min | +2.9 stops |
| 16 min | 2 h 34 min | +3.3 stops |