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Why I Rate T400 At ISO 100 (see Tech Notes)


Film rated at ISO 100, 45mm, f4 lens.

This is a detail from another picture in this portfolio. Quite a few photo.netters have emailed me asking why I rate the T400 film at ISO 100. The detail contains a lot of black elements in it - uniforms, bikes etc. - but these have (and had in real life) details that were important to the shot. T400 (and Ilford XP2-super) is a contrasty film at ISO 400. That is, you get fine grain, but black shadows. If you lighten up the shadows they are grainy and noisy. If you don't want black shadows and favour more "realistic" shadow details, rating the film at ISO 100 (2 stops overexposed) allows more light from the shadows to fall on the film, giving darker areas more detail and less grain. There seems to be no penalty in doing this, including the convenient fact that T400CN is readily available at almost any half-way decent photo store in Europe.

I get my T400 films processed at the local minilab and there has never been a problem. They're ready in 1/2 an hour, no messy chemicals, no fuss. Cost? AUS$6.00 (about USD$3.00). The way the emulsion is designed (although please don't ask me for a technical explanation) means that there is no really difficult or even very appreciable increase in neg desnity.

This is a real example of "something for nothing" (if you don't mind the slower speed). Kodak's own tech note for the film says you can use it from ISO 25 to ISO 1600, putting the median value at around ISO 200, not ISO 400. I go one stop further to ISO 100 because I still have a little trouble getting a "realistic" effect in my shadows at ISO 200. This last step is a matter of prererence.

The zoomed detail also show how bloody sharp the Xpan's 40mm Fujinon lens really is.You might also note how sharp that Fuji lens is on the XPan by comparing the detail with the original.

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