Measured film base for Kodak Portra 400, read off the clear rebate under the three narrow bands. These are the numbers the app uses as the denominator for every frame on a roll of this stock.
#Base density, in counts
| Channel | Band | Counts |
|---|---|---|
| Red | 665 nm | 236.5 |
| Green | 525 nm | 448.5 |
| Blue | 450 nm | 531.5 |
#How it was measured
Portra400 WRGB · 36 frames · lines-with-flat przez PROCESS (instrument aplikacji; ring polkowy 1.017 B vs linie 1.038 — konsument tabeli mierzy sie liniami, wiec wpis niesie linie)
That line is the provenance: which frames it was pooled from, and the spread between them. A base is not a constant of the emulsion — it is a measurement of a batch, with a tolerance.
Note
This stock also has a white-light pair measured: R 238.1 · G 403.3 · B 509.5. That is what the same base reads as under white light rather than three bands — useful only for comparison, since the channels overlap there.
#If yours reads differently
It may well. Emulsion batches vary — a green slope of [1, 1.8, 1] was confirmed independently on two different stocks — and your light is not necessarily the one these were read under. Post what you measured and on what rig, and it becomes a second data point rather than a disagreement.