Tidal Grain

Reference

The tables that get looked up with cold hands. Everything is a starting point; the last word belongs to the negative.

Long exposures

Past about one second film responds less than the meter promises. The makers of most of the films used here publish one number per film: raise the metered time, in seconds, to that power and expose for the result.

FilmPowerMetered 30 sMetered 2 min
Ortho Plus1.251 min 10 s6 min 35 s
FP4 Plus1.261 min 15 s6 min 55 s
Delta 1001.261 min 15 s6 min 55 s
Kentmere 1001.261 min 15 s6 min 55 s
Kentmere 4001.301 min 25 s8 min 25 s
HP5 Plus1.311 min 25 s8 min 50 s
Pan F Plus1.331 min 30 s9 min 45 s
Delta 32001.331 min 30 s9 min 45 s
Delta 4001.412 min14 min 15 s
SFX 2001.432 min 10 s15 min 40 s

Worked through for four of them:

MeteredFP4 PlusHP5 PlusPan F PlusDelta 400
1 s1 s1 s1 s1 s
2 s2.4 s2.5 s2.5 s2.7 s
4 s5.7 s6.1 s6.3 s7.1 s
8 s14 s15 s16 s19 s
15 s30 s35 s37 s46 s
30 s1 min 15 s1 min 25 s1 min 30 s2 min
1 min2 min 55 s3 min 35 s3 min 50 s5 min 20 s
2 min6 min 55 s8 min 50 s9 min 45 s14 min 15 s
4 min16 min 40 s22 min24 min38 min
1 s 2 s 4 s 8 s 15 s 30 s 1 min 2 min 4 min 1 s 10 s 1 min 10 min 40 min No correction FP4 Plus HP5 Plus Delta 400 Metered time

Both axes of the chart are stretched so that equal steps are equal numbers of stops. A film that needed no correction would follow the dotted line. Acros II very nearly does: its maker asks for nothing up to two minutes and half a stop beyond. Tabular-grain films from other makers sit between that and the curves above.

At dusk the light falls while the shutter is open. On any exposure longer than a minute, meter again half-way and add what was lost. More on this in the note on dusk.

Grey filters

StopsDensityFactor1/125 s becomes1/30 s becomes
10.32×1/60 s1/15 s
20.64×1/30 s1/8 s
30.98×1/15 s1/4 s
61.864×1/2 s2.1 s
103.01 024×8.2 s34 s
133.98 192×1 min 5 s4 min 35 s
164.865 536×8 min 45 s36 min

These are times on the dial. Anything over a second then goes through the table above. Ten stops and a red filter make thirteen; ten and six make sixteen, and at sixteen the strongest filter is patience. Coloured filters and their factors are in their own note.

Developer temperature

Times on the sheets are for 20 °C. In a house without heating in the darkroom the developer is rarely there. A fair rule is nine per cent less time for each degree warmer, nine per cent more for each degree colder.

Developer atMultiply by7 min 30 s becomes11 min becomes13 min becomes
18 °C1.209 min13 min 15 s15 min 45 s
19 °C1.108 min 15 s12 min14 min 15 s
20 °C1.007 min 30 s11 min13 min
21 °C0.916 min 45 s10 min11 min 45 s
22 °C0.836 min 15 s9 min 15 s10 min 45 s
23 °C0.765 min 45 s8 min 15 s9 min 45 s
24 °C0.695 min 15 s7 min 30 s9 min

Below 18 °C some developing agents slow down more than others and the rule stops being fair. Warm the bottle in a basin instead.

Kept elsewhere