Why 160ASA?

[gbenson]

This is probably a really stupid question, but why are both Kodak and Fuji's pro colour films in 160, 400 and 800? Why not 100, 400 and 800, or 200, 400 and 800? I tend to have 160 colour and 400 B&W film on the go at once, and much as I love Portra 160vc, but I may start treating it as 100 or 200, just to make my life easier...

 

[hrst]

Well, why not?

There have been improvements on these films over the years and the speed has gone up.

There are also ISO 125, ISO 250, ISO 320, ISO 64 etc. films.

Almost every camera or meter has exposure setting at 1/3 stop intervals so I really can't see how it would make your life easier to downrate or uprate it just for this reason.

It's not so weird, it's just its speed.

 

[2F/2F]

Off the top of my head, I know of films that are (or were) 25, 32 (Pan-X), 40 (MP film), 50, 64, 80 (Ilford Ortho), 100, 125, 160, 200, 250 (MP film) 320, 400, 500 (MP film), 800, 1000, and 1600. The only ones missing from 25 to 1000 on my list are 640 and 1250. So, the answer to why 160 is because the films is question are ISO 160 films.

 

[darkosaric]

And if you look in DIN scale it is not so strange: ... 18, 19, 20, 21, 22, 23, 24 ...

 

[Bruce Watson]

This is probably a really stupid question, but why are both Kodak and Fuji's pro colour films in 160, 400 and 800?

Stupid? No. But are you bored? I can understand how someone might think that. But not me. No, not me.

The answer perhaps is that when the engineers got done meeting their design targets for graininess, sharpness, color balance, tonality, saturation, etc. the resulting emulsion tested out to be ISO 160. It's not good or bad, just is. What possible difference can it make? Is it really that much more effort to turn the ISO dial on a camera or meter one third of a stop farther? Really?

These films are so frickin' good that I'll jump through hoops a lot bigger than 1/3 of a stop on an ISO dial for 'em. A *lot* bigger. I can't believe how good we film photographers have it right now! I'm not about to quibble over ISO numbers.

 

[fotch]

What Bruce said, I agree.

 

[msage]

Don't worry about why it's 160 and not 200 or 100. Go out and make photographs!

 

[MattKing]

At least on the Kodak side, the 160 ISO reflects the improvements in emulsions. The predecessors were various Vericolor emulsions, with Vericolor III being ISO 160, Vericolor II being slightly slower - 125 ASA (yes, that is ASA) and earlier versions being older than I know about or remember.

The speed ratings also do or did vary with the light source (Daylight vs. tungsten or ...)

 

[keithwms]

Definitely not a dumb question. The reasons are likely technical (as already mentioned). In the design phase, who knows, they may have aimed for 100 and found 160 was doable with new materials, or they may have been aiming for 200 but couldn't quite get it.

I suppose that an important constraint is how it will be processed, you don't want weird processing times just for one film- and there really isn't a lot of play in the c41 development times. Also, if Kodak or Fuji were to, say, market a 100 speed film like reala as 160, they would get an earful very quickly because a lot of very careful photographers would do their tests and conclude they can only get to 160 by pushing the development time.

Of course, some photographers consider the box speeds of the neg films to be a bit high. I often rate 160 colour neg films at 120-160, the 400 films at 320, the 800 films at 640, and the (pushed) 3200 films at 1600. Some people go a lot further than that. It all depends what you're after, what kind of light and contrast you have etc.

 

[perkeleellinen]

The only ones missing from 25 to 1000 on my list are 640 and 1250.

Scotch 640T!

 

[markbarendt]

This is probably a really stupid question, but why are both Kodak and Fuji's pro colour films in 160, 400 and 800? Why not 100, 400 and 800, or 200, 400 and 800? I tend to have 160 colour and 400 B&W film on the go at once, and much as I love Portra 160vc, but I may start treating it as 100 or 200, just to make my life easier...

Personally I'm comfortable with doing the math with either a 160 or 400 base, I actually find it fun.

I do though understand the simplicity of what you want and I think there is enough latitude in the film so that you would not be disappointed at 100 with a 160 film. I'd suggest a 400 speed film if you want to shoot at 200.

The 400 speed films typically have more than enough detail/sharpness for my style, I've yet to be disappointed by them, and I'll happily shoot them at 200, 100, or even 50 if that's all I have handy.

Most of the reason I shoot 160 iso films is that lately I'm liking slower shutter speeds and larger apertures for effect and if I'm planning on getting down into the 50 or 40 or 20 EI range; I'd rather have the 160 film.

I re-rate knowing that I'll be working a bit harder with my enlarger.

 

[JPD]

Agfacolor Portrait was another 160 ASA-film. I believe it's a trend. 200 ASA was/is a popular speed for amateur photographers...

-"What film speed do you use?"

-"160".

-"I didn't know films with that speed existed! "

-"I'm a professional. "

The only ones missing from 25 to 1000 on my list are 640 and 1250.

Kodak Royal-X 1250 ASA!

 

[benjiboy]

And if you look in DIN scale it is not so strange: ... 18, 19, 20, 21, 22, 23, 24 ...

This would seem to me to be the most logical answer to the question, although I must admit that all the years I've been using these pro portrait films it never occured to me to query why, some things in life you just have to accept.

 

[Ektagraphic]

Allows them to not have to make two diffrent films...ISO 100 and 200. 160 is almost right in the middle...That's my thought

 

[Bob Carnie]

What I like about 160 ISO for colour neg is that it is approximately the same rating I give HP5 when working with Pyro Dev.
Since I use the sunny 16 rule things become nice and easy.