Development time

Ilford FP4 Plus in Perceptol

12:00 at 20°C, stock dilution, box speed.

Start timer · 12:00

Time

12:00

Standard

Dilution

Stock

Temperature

20°C

Box speed

ISO 125

B&W

All 3 times

Dilution	EI	Time	Temp	Agitation	Timer
Stock	125	12:00	20°C / 68°F	Standard	Start timer
1+1	125	15:00Not yet verified	20°C / 68°F	Standard	Start timer
1+3	125	20:00Not yet verified	20°C / 68°F	Standard	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
15:00	13:26	12:00	10:48	9:36	8:38	7:48

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
1+1	150 ml developer + 150 ml water	250 ml developer + 250 ml water
1+3	75 ml developer + 225 ml water	125 ml developer + 375 ml water

How they work together

Perceptol: Moderate acutance, normal contrast. Extremely fine grain, optimised for enlargement.
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: Produces extremely fine grain.
Fine grain with slightly less effect than stock.
Economy dilution for fine grain.

FP4 Plus in other developers

ID-11