Reciprocity Failure Calculator
Use only a manufacturer’s Tc = Tm^P formula for the exact film and version, within its stated range.
Use only a manufacturer’s Tc = Tm^P formula for the exact film and version, within its stated range.
Tm and Tc are numeric seconds; P is dimensionless. Added time = Tc − Tm and can be negative.
Do not use this model for digital sensors or other films. No film values are built in. Consult the current manufacturer instructions.
Source reference: ILFORD — Film Reciprocity Failure Compensation (PDF)
A QUICK WALKTHROUGH
How to use this tool
- Metered exposure Tm (seconds)
- Manufacturer exponent P
- Calculate
Formula and units
Tc = Tm^P. Tm and Tc are numeric seconds; P is dimensionless. Added time = Tc − Tm and can be negative.
Manufacturer range
Use only a manufacturer’s Tc = Tm^P formula for the exact film and version, within its stated range. Do not use this model for digital sensors or other films. No film values are built in. Consult the current manufacturer instructions.
GOOD TO KNOW
Common questions
Are inputs uploaded?
No. All calculations run locally in your browser.