Kodak films: what does X represent?

[dwross]

I don't know but guess that it goes back to the glass plate speeds...

Slow, Ordinary, Rapid, Extra Rapid, Double Extra Rapid.

Where the X is from Extra.

I've had a hard time finding how these speeds translate to ASA/ISO speeds. Seems any reference that knows these speeds predates ASA...

Bill,

I believe you've mixed lists. "Ordinary" doesn't refer to an emulsion speed, but rather to the plate being colorblind, i.e. unsensitized to anything but UV and a bit of violet light. It is by default very slow, but an ordinary plate can still be different degrees of slow.

It's been my understanding for so long that I've forgotten where I learned it (and could therefore be wrong!) that the X designation referenced chemists' notation for halides (in photography: chloride, bromide, and iodide). AgX is shorthand for any silver halide.

[bsdunek]

Fast above slow. Hmmm, see Kofron et. al. for that one! Yes, that ordering is used in color films and is a patented Kodak method of speed vs grain for some films.

And the X film designations at this point are just a guesstimate. Next chance I get, I'll ask George Eastman, but I am not in a hurry to ask him if you get what I mean.

PE

Ya, but then you won't be able to get the answer back to us.

[Ian Grant]

Seems the X family was larger wit Ortho X as well, see 1940 advert which includes Tri X:



In contrast Ilford had just introduced their second generation of modern films FP2 & HP2.

Ian

[dynachrome]

In High School I bulk loaded film for my Minolta 16 PS. The film I used was Eastman Four-X single edge perf motion picture film. It had an ASA speed of 500. Double-X was 250 and Plus-X was 125. In the future if I want to use the Minolta I will probably get a slitter and use 35mm stock. I don't think the Minolta uses the perforations anyway.

[strix1973]

It may be wrong but I recall reading that in 1937 or 38 the x designations were added to newly designed still camera films to distinguish them from motion picture film due to their having an antihalation layer and and could be developed to a higher contrast as well as being equally efficient in daylight and artificial light. Panatomic x was the still version of the cine Panatomic with finer grain for enlargements. Plus x was the still version of Kodak cine ss pan and had 50% more speed.

[nworth]

It is probably just a marketing label. There have been a lot of X films, and not all have been commercial mass market items. Not all have been black and white, either (e.g. Kodacolor-X). Some have been motion picture films (Eastman Plus-X, Background-X, Double-X, Tri-X, 4X, XT, etc.)

[Photo Engineer]

All films have an antihalation layer of some sort or another. You have to go way way back to find some without such protection.

PE

[Ian Grant]

It may be wrong but I recall reading that in 1937 or 38 the x designations were added to newly designed still camera films to distinguish them from motion picture film due to their having an antihalation layer and and could be developed to a higher contrast as well as being equally efficient in daylight and artificial light. Panatomic x was the still version of the cine Panatomic with finer grain for enlargements. Plus x was the still version of Kodak cine ss pan and had 50% more speed.

No because Kodak introduced exactlysame films as Motion Picture film around the same time in 1938/9. The X was similar to Tmax just a new family of films and to distinhuish them from earlier products so just a marketing tool as nworth says.

Welcome to APUG BTW

Ian

[walbergb]

The answer you seek is simple: the letter W was already spoken for and X was the next available letter

[jloen]

Two days ago my contractor told me that PEX tubing was named for polyethylene that is cross-linked, "so they put an X on the end". I immediately thought of Tri-X film. But there may be no connection...