🔬 Deep cuts
Film makers publish far more than development times. Their data sheets measure grain in the negative and in the print, say how they rate a film's speed and why a 3200 film measures 1000, give the base it is coated on, the code cut into a sheet's edge and how little water a wash really needs. These pieces read those documents closely and cite every figure.
Deep cuts · 🤿 deep end · 3 min
The three numbers that answer how grainy and how sharp a film is, measured by the people who make it, and what they say about format.
Rms granularity, lower is finer: Acros II 7 · T-Max 100 8 · T-Max 400 10 · Tri-X 320 16 · Tri-X 400 17 · P3200 18
Deep cuts · 🎯 regular · 2 min
Ilford and Kodak say in their small type how they rate film, why the 3200 films measure 1000, and which 400 film gains nothing from pushing.
ISO speed method: ISO 6, from the foot of the characteristic curve
Deep cuts · 🎯 regular · 2 min
A black-and-white film made of dye that gains nothing from pushing, and a panchromatic film that sees to 740 nanometres.
XP2 Super process: C-41; replenish as an ISO 200 colour negative
Deep cuts · 🎯 regular · 2 min
How a time at 20 °C becomes a time at 24 °C, why Ilford refuses anything under five minutes, and what that means on a hot day.
Ilford's example: 8:00 at 20 °C = 5:30 at 24 °C
Deep cuts · 🌱 first roll · 2 min
The small cuts in the corner of every sheet tell you which film it is and which side the emulsion is on, if you know how to hold it.
Reading the code: portrait orientation, notches top right edge: emulsion faces you
Deep cuts · 🎯 regular · 2 min
What the wash removes, Ilford's three-tankful film method, and the timed sequence that makes fibre prints last.
Film wash, spiral tank: same temperature ±5 °C; invert 5, then 10, then 20 times with fresh water each time
Ilford Delta 3200 measures ISO 1000. The 3200 on the box is Ilford's recommended meter setting, with extended development.
Kodak gives T-Max P3200 a nominal speed of EI 1000 in its T-MAX developers, and EI 800 in its other developers.
Pushing XP2 Super gains no practical speed. Ilford's answer is to rate it at EI 800 and process it normally.
Kodak's July 2025 sheets list Portra 400 in 135 and 120 on a 0.10 mm ESTAR polyester base.
Ilford coats HP5 Plus on 0.125 mm acetate in 35mm, 0.110 mm acetate in 120 and 0.180 mm polyester for sheets.
On Kodak's Print Grain Index, 25 is about where grain becomes visible and 4 units is the smallest step 90% of people notice.
An 8x10 from a 35mm Portra 400 negative scores a Print Grain Index of 59; from 120 it scores 37.
Fujifilm Acros 100 II has a diffuse rms granularity of 7 and resolves 200 lines per millimetre on a high-contrast chart.
Kodak rates Tri-X 400's rms granularity at 17 and calls it fine. T-Max 100's is 8.
Kodak's Ektachrome E100 needs no filter or exposure correction anywhere from 1/10,000 to 10 seconds.
Ilford SFX 200 is sensitive into the deep red, to about 740 nanometres: behind a deep red filter, skies go almost black.
Ilford's chart turns 8 minutes at 20 °C into 5:30 at 24 °C, and refuses anything under five minutes: uneven development.
Ilford's film wash is three tankfuls of water: invert five times, then ten, then twenty.
Ilford rates its films by practical evaluation in ID-11, not by the foot-speed criterion the ISO standard uses.
Hold sheet film upright with the notches at the top right and the emulsion is facing you.
Kodak warns its Print Grain Index may understate grain from condenser enlargers, with their more specular light.
A metered 30 seconds on Delta 400 needs about 121: Ilford's reciprocity factor for it is 1.41.
Foma says Fomapan 100 takes one stop over or two stops under without any change in development.
T-Max 100 resolves 200 lines per millimetre on a 1000:1 chart, but 63 on a low-contrast 1.6:1 chart.