Development time

Ilford FP4 Plus in Diafine

6:00 at 20°C, stock dilution, EI 250 (+1 stop).

Start timer · 6:00

Time

6:00

Minimal

Dilution

Stock

Temperature

20°C

Box speed

ISO 125

B&W

Development time

Dilution	EI	Time	Temp	Agitation	Timer
Stock	250+1 stop	6:00	20°C / 68°F	Minimal	Start timer

EI is the speed the film was rated at when shooting. Times marked “not yet verified” come from secondary sources and haven’t been checked against a manufacturer datasheet.

Other temperatures

18°C	19°C	20°C	21°C	22°C	23°C	24°C
7:30	6:43	6:00	5:24	4:48	4:19	3:54

Calculated from the 20°C time using Ilford’s temperature compensation factors, not taken from a datasheet. Most B&W developers behave well between 18°C and 24°C.

Mixing

Dilution	300 ml (one 35mm roll)	500 ml (one 120 roll)
Stock	Use as mixed, undiluted	Use as mixed, undiluted

How they work together

Diafine: Fine grain, high acutance, normal contrast. Good shadow detail with effective speed increase.
Ilford FP4 Plus: Often considered a benchmark for medium speed B&W. Notable sharpness and fine grain. Well-suited for high-quality enlargements.
Notes on this pairing: 3 min Bath A + 3 min Bath B. 35mm and roll film.

FP4 Plus in other developers

510-Pyro