Originally Posted by znapper
That's funny, Foma also claim that their 100 ISO film is 100 and their 400 ISO film is 400, which they aren't in reality.
Delta gives paler lips on my models than Acros, which, again, gives paler lips than Foma. This is one of the more important aspects when i shoot, so that it why I tend to prefer certain films over the others.
Foma may _claim_ their red-sensitivity is such and such, but in reality (and luckily), my experience is that it really isn't, i get consistently darker lips on models with Foma, interpret that as you may.
In my experience, Ilford, Fuji and Kodak is usually much more consistent and correct in their charts than Fomapan.
Yes, Foma do (or at least did) get a bit creative with developer choices for ISO speeds, but that is allowed under ISO rules. About 20 years ago I actually plotted D/Log E curves for Foma 200, and found that it is all but identical to Ilford FP4 Plus in most developers, including a couple of speed increasing developers which put it close enough to ISO 200 to allow it to be sold as such. Which is exactly what they showed on their spec sheet.
Why would they lie about red sensitivity? Sure, it's possible that they changed sensitizing dyes without updating the spectrography, but it seems more than a little unlikely. And in any case, blue filtration will knock back red sensitivity and darken lips: higher red sensitivity means paler lips, not lighter which is what you are saying unless I am misreading you.