2 questions about film

[Aaron_3437]

1. Do films with low b+f do a better job than those with high b+f? 2. Why do slow speed films do better in low contrast situation?

Thanks!

[Donald Miller]

Low b+f films will normally enable the film to offer higher density range (contrast) then those that exhibit high b+f. High b+f does nothing other then extend the printing exposure time.

Typically low speed films will offer the opportunity for greater density range expansion then those that are high speed films. There are some notable exceptions to this among those are Tmax 400.

[ramin]

It’s all about exposure latitude. 100 ISO films do have a low film base plus fog density but are not capable of recording more than 5 stops; it is probably because of their thinner emulsion. If your scene has a low contrast like a cloudy gray day in London, TMX or FP4 will do the job. More over printing a 100 ISO film is easy too since its latitude fit to that of printing papers. I would say the only difference apart from dynamic range between a low b+f and a high b+f is their local contrast in the toe range.

Cheers

[Brian Ellis]

"100 ISO films do have a low film base plus fog density but are not capable of recording more than 5 stops."

100 ISO films aren't capable of recording more than five stops? I don't think I've ever heard that before. That would mean zone system expansion couldn't be done with ISO 100 films, which seems odd. I often develop T Max 100 to N+1 (i.e. 8 stops from Zone I, 6 stops from Zone III), occasionally to N+2 (9 and 7 stops from Zones I and III respectively). In workshops I've attended people like Bruce Barnbaum and Don Kirby talked about getting 12 and 13 stops, though I don't offhand recall what films they're using when they talk about that. Could you elaborate a little on your statement (e.g. what's the basis for it, why is it so if it is so?).

[Aaron_3437]

Would it be justified to say that the reason one uses a high speed film (example HP5) is mainly for the purpose of higher speed? That a low speed film is most ideal in any situation if the exposure speed is not an issue? If that's true, would an ASA200 film (example Classic Pan 200) be a good compromise if one chooses to use only one film?

[Chris Gittins]

Ramin, I'm puzzled by your "five stops" comment too.

I use ISO 400 film (HP5) because I need the higher speed. The fact that faster films are generally lower contrast also works well for me because I tend to shoot subjects with a wide subject brightness range. Compared to FP4 (ISO 125), I've just found HP5 a little easier to work with for the things I've been doing. (The FP4 development times end up being really short so its harder to control the contrast in the negs.) That said, I really like FP4 when I don't need the speed and am working with relatively normal brightness ranges. I print 4x5 negs at 8x10 and 11x14. I haven't found that's enough enlargement to notice any differences in grain between the two.

As a general rule, slower films have finer grain. A notable exception to that may be BPF200. I haven't done enough with it to say one way or the other, but I've seen many posts indicating that it's quite grainy.

I'd say the three things to consider are speed, grain, and contrast.

Chris

[paulr]

the "five stop" comment seems strange to me as well. I've used agfa pan 100 and tmx 100 for years; my normal development yields about 10 stops range (or did you mean +/- 5? this could be the same thing ...) N- development gives a solid 11 or 12 stops. I have no idea what would be possible with water bath, 2 solution development, special low contrast development (like POTA) or other techniques ... but I'm sure a lot more than I've ever even tried to get. Even my N+, high contrast development gives more like 8 stops range.

[james mickelson]

The 5 stop limitation is for most papers. Papers are always the limiting factor. Never the film (most pan films). The papers can be teased a little but the majority of papers are around 5 stops.

[paulr]

James, i take it you're talking about the final visible contrast range of the paper?

[Chris Gittins]

>The 5 stop limitation is for most papers. Papers are always the limiting factor. Never the film (most pan films). The papers can be teased a little but the majority of papers are around 5 stops.

OK, that makes more sense if you're talking about negative density range/paper exposure scale rather than subject brightness:

five stops = 2^5 = 32 = 10^1.5

Seems a bit long, but I think I understand the argument now.