Tri-x ASA and ISO ?

[bob_levittan]

I'm a little confused about the ASA markings on Tri-x film. 35mm is 400, that I

know. I thought that 120/220 film were both 400, but it looks like 120 is 400

and 220 is 320. Is that right, and how come?

 

Also, 4X5 Tri-x looks like it's 320, but on Calumet's web-site, the item

heading says, "Kodak TXP 4x5 25 Sheets 4164 320 ISO" but the description below

says, "KODAK TRI-X Pan Film is a high-speed (ISO 400/27)."

 

I'm planning on doing personal ASA tests as described in Fred Picker's Zone VI

book, but in there is says things like "expose a zone I frame at 100% rated

ASA, then at %200 the ASA, then at 75% the ASA," etc. So I need to start at the

correct ASA.

 

I also don't know - why ASA and ISO? Is there a difference? Is ASA defunct?

[john_shriver]

There are two DIFFERENT Tri-X films. There is Tri-X (now 400TX), and there is Tri-X Professional 320 (now 320TX). Of course, the 400 speed Tri-X also says professional on the box, now that there's no "amateur" B&W film market.

 

The 400 speed film is available in 35mm magazines, 35mm long rolls, 70mm long rolls, and as 120 single rolls. The prefix is TX.

 

The 320 speed film is available in 120 and 220 pro-packs (5 rolls), and in sheet film sizes. The prefix is TXP.

 

The 320 speed film is a portrait film, with a different HD curve, intended for controlled lighting (studio), and with a retouching base (you can write on it with pencil).

 

The standard for measuring film speed is presently maintained by ISO (not an acronym, The International Organization for Standardization). It used to be maintained by the American Standards Association (ASA, now ANSI, the American National Standards Institute).

[michaelging]

There is Tri-x which is a ASA 400 film , which comes in various formats. There is also a film called Tri-x Pan film which is ASA 320 , which was made more as a studio film.To me it has a little less contrast and more middle tones. It also has a retouching surface, which portrait galleries used to use to make you beautiful before photoshop was invented.

[kelly_flanigan1]

Tri_x came out during WW2 in sheet films; it was an asa 200 product. In came out in 35mm in 1954. In became an asa 400 product in the late 1950's/early 1960's; the safety factor was removed; asa was redefined. ASA of 320 is many times in pro tri-x; often with a retouching base; 400 in amateur tri-x. The toe region is different on these products. 1954 was also when trix for kids cam out; the breakfast cereal. Many sites wrongly mention that tri-x came out in 1954; it deid in roll films, but it existed even in ww2 in sheet form.

[Mike Gammill]

What Kelly said. I found a back issue of Modern Photography from 1960 which confirms what he said about safety factors. Most serious photographers rarely rated films at box speed in those days. For example, Plus-X in 1959 was an ISO 80 film, but was often exposed anywhere from an E.I. of 160 to 320 depending upon whether the lighting was flat or contrasty. Some ratings were revised later. For example when the safety factor was removed Panatomic-X went from 25 to 40, but was later revised to 32. I have an unused roll dated 1962 that confirms the ISO 40 rating.

My point- even w/o safety factor you should perform tests to see what E.I. is right for your tastes. Some prefer TX at box speed, but others may rate it at 200 to gain tonal range or 800 or higher under flat lighting.

[rothelle]

The best way to understand it is at the web site of Kodak;-)

http://www.kodak.com/global/en/professional/products/films/bw/triX2.jhtml<div></div>

[rodeo_joe1]

The difference between 320 and 400 ISO/ASA really isn't worth worrying about. It's about 1/3rd of a stop, which is nothing in terms of a B&W film exposure. And I'll bet that the light could easily change by that amount between taking a meter reading, setting the camera and taking the shot.

 

Set your meter to 360 ISO and use TX and TXP interchangeably. As long as you get the development right you won't see any difference between the two.

 

Try this: Take a series of shots of the same subject, under the same lighting, with one whole stop difference in exposure between frames. You'll be surprised how little density change there is between the negatives. You'll also see that plus or minus a whole stop makes very little difference to the printability or scanability of a negative.

 

The ISO rating is only a guide to correct exposure after all.

[keith_lubow]

To do those tests, you just start with the box speed. You will bracket around it anyhow, which is the point of the test. The tests will give you a useful speed to use that will cause a zone I placement or a zone I fall to have the proper amount of negative density to be rendered as an actual zone I print value upon normal printing onto a grade two paper; not above or below. It does not actually change the physical characteristics of the film. All this does is give you an ASA number to plug into your exposure calculations that will give you the ability to predictably assign low-end shadow values certain negative densities that will eventually be made into certain print values upon normal printing onto a grade two paper.

 

Then, using the ASA number you have decided to use for the placement of low-end values based on your test one, you will expose blank (lens cap on), zone V, and zone VIII over and over, and try different development times until you find the one that gives a zone VIII placement the density that becomes an actual zone VIII print value upon normal printing onto a grade two paper.

 

Then, to find out your pluses and minuses, you shoot however many stops you are trying to figure for above or below zone VIII, and test development until that placement ends up being the same density you would expect from a zone VIII placement with normal development. This means for proper N-1 time, a zone IX placement should have the same density as a zone VIII placement and N development. This means for a proper N-2 time, a zone X placement should have the same density as a zone VIII placement and N development. This means for a proper N+1 time, a zone VII placement should have the same density as a zone VIII placement and N development. This means for a proper N+2 time, a zone VI placement should have the same density as a zone VIII placement and N development. And so on and so on ad nauseam.

 

Then, in general practice, you will look at a scene, meter different parts of it, and finally decide to expose in a way that will render one of the luminance values you have noted as a particular negative density that will eventually be realized as a certain print value upon normal printing onto a grade two paper. This is called placement, and it is most often done with the lower luminance values at the scene of the exposure. When you place one luminance value, all the other ones fall at certain distances above and below it. You are good, though, because you have notated how many "stops" (incorrect but highly practical terminology to use) away all these values are. Then, when you develop, you decide whether the luminance range at the scene was right on for the print you envisioned. If not, that's when you alter development using the times from test three.

 

Seems to work in practice, for me at least.

 

Keith

[kelly_flanigan1]

With the old Kodak F-5 B&W Film booklete of 1976 I was married to; there are different pages for Tri-x and tri-x pro. There is more than just the 400 and 320 asa differences; and the retoucing base on the 320 product. the DlogE curves are different. The pro version has a long toe; and doesnt droup/poop out in the highlight region. The regular asa 400 product has a shorter toe, a so called medium one. For astronomy usage in the 1970's I prefered the amateur/regular/400 product; it could be overdeveloped and the toe budged somewhat. The pro/320 product is good for portraits that needed retouching, commerical work where highlights are important such as a wedding dress, glassware, clothes.

[kelly_flanigan1]

The differences in speed of 320 versus 400 are minor; almost not important in the scheme of things.<BR><BR>What matters is these two films are different breeds of tri-x; they develop differently; respond to light differently; they have different development times; different film bases. One poops out in the highlights; another doesnt. The MTF curves are even different; the pro film has a lower MTF. A simple thing to remember is the 400 product often is better for low light; the 320 for highlights; ie amateur are low life; pros are highlife.:)

[keith_lubow]

Kelly has hit the nail on the head. They are, simply put, different films.

 

In most uses, a film that "poops out" in the highlights is an absolutely invaluable tool for controlling contrast. And, and Kelly mentioned, you might choose a different tool (the "amateur" version) in certain situations.

 

Keith

[bob_levittan]

While I'm at it, does anyone know a lab in the New York area that can do the zone I densitometer check for me (which ASA gives me a placed zone I density of .08 to .1 above film base plus fog) ? Actually it doesn't have to be in New York, I wasn't going to drop it off by hand anyway.

[keith_lubow]

Bob,

 

Any pro lab worth its salt will have at least two of them. If you are real nice, they will probably let YOU do it. A and I in L.A. has let me use their densitometer for all of my tests, free of charge. They use them for process control, and it's no skin off their back if someone comes in for ten minutes and pokes around on them.

 

Keith