Reciprocity

Ilford Ortho Plus long exposures

What a metered time becomes on Ortho Plus, and the stops it adds — worked out from Ilford’s own data, never past it.

Form T-2

Your metered time

Tc = Tm^P for metered times over 1 s; 1 s or less needs no correction (P = 1.25)

The maker’s reciprocity data ↗

Table 1

At a glance

Metered	Expose for	Added
1 s	1 s	—
2 s	2.4 s	+0.2 stops
4 s	5.7 s	+0.5 stops
8 s	13 s	+0.7 stops
15 s	30 s	+1 stops
30 s	1 min 10 s	+1.2 stops
1 min	2 min 47 s	+1.5 stops
2 min	6 min 37 s	+1.7 stops
4 min	15 min 45 s	+2 stops
8 min	37 min 27 s	+2.2 stops
16 min	1 h 29 min	+2.5 stops

Other films with reciprocity data

The reciprocity calculator ›