Film & darkroom
Compare your processing thermometers
Find disagreement before starting the film.
Two instruments may give different readings even when placed in the same bath.
Compare under the same conditions
Use each thermometer according to its instructions in a suitable common test bath. Allow readings to settle and record the difference. Do not compare one air reading with another instrument immersed in liquid. A comparison reveals disagreement; it does not by itself establish which instrument is accurate.
Resolve the practical uncertainty
Check the required tolerance for the selected process and use an appropriate verified instrument. Follow the product’s temperature guidance rather than averaging contradictory readings casually. Record the thermometer used in the session log, so a later change of instrument is visible when comparing results.
Evidence: Technical data sheet
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.
- ILFORD PHOTO — ILFOTEC DD-X technical dataTechnical data sheet