I have been exposing Kodak T400CN at about 320 to 350 ISO as at 400 (on the box) it gives slightly underdeveloped negs by half a stop. So its real speed is slower than what kodak claims. Apparently Tri-ex 400 B&W is similar. Can people please state what they find to be the true and REAL speeds of the following films so I dont have to test several rolls of film trying to find verifify what is best:

1). Kodak Tri-ex 400 2). Ilford FP4 125 3). Fuji Velvia (aparently its true rating is slower also) 4). Provia 100F?

Cheers,

-- sparkie (sparkie@mailcity.com), April 13, 2002

Answers

This is what i have found for my personal use:

1. don't use enough to say
2. don't use enough to say
3. 40ISO (not the 50 indicated)
4. 100ISO (as indicated), but if pushed one stop i use 180 instead of 200, and if pushed two stops i use 320 instead of 400

-- Matthew Geddert (geddert@yahoo.com), April 13, 2002.

this does not mean that the "true rating" is wrong, all it means is that i want to focus on things like shadow detail, or highlights or etc... the only thing that matters is if the image is exposed the way you envision it... some people consistently "underexpose" a bit (based on the "objective" rule to get an average of neutral grey) their shoots because they want them to be dark and gloomy, others overexpose a bit consistently because they want them to be more vibrant. What matters is that the shots are exposed the way you envisioned them to be when you pressed the trigger.

-- Matthew Geddert (geddert@yahoo.com), April 13, 2002.

We don't all use the same lab. We don't all use the same chemistry. Not all labs use the same brand of control strips. Fuji control strips yield higher effective film speeds than Kodak control strips, etc, etc, etc.....

Sorry, but if you want accuracy with your own lab or your own home processing, YOU have to do the testing and find what works for you. Testing several rolls of film really isn't that hard is it?

-- mark lewis (mark@markpix.com), April 13, 2002.

What Mark said.... adding its even more variable on black and white material.

-- Charles (cbarcellona@telocity.com), April 13, 2002.

That's a very complicated question. As far as the slide films go, their ratings are probably accurate, but many people choose to underexpose chromes by a small amount to increase color saturation. Slide film has very little latitude, especially for overexposure.

As far as color neg, and T400, if processed properly, they should give decent results at their rated speeds. But when I'm forced to shoot color neg film (which is the only time I use it), I usually shoot it a half stop over or so.

As far as the BW, I shoot Tri-x at it's rated speed, 400, processed in Rodinal with times I came up with after tons of testing. Rodinal gives good film speed and an incredible tonal range. It is somewhat grainy though, so not everyone likes the look of it. With other developers I've shot Tri-x successfully at speeds from 200-800. It would be difficult for you to take my (or anyone else's) times and use them for yourself. We all process film a little differently. You can learn a lot about how your film will react in different circumstances by doing some testing. Experiment with one film at different speeds and with different developers. The beauty of B&W is that you have so much control. It's worth the trouble to do some testing.

-- Noah Addis (naddis@mindspring.com), April 13, 2002.

The "true" speeds of the films are absolutely as on the box--it's measured according to a very strict standard, carefully defined (ISO=International Standards Association). But as with the car mileage you see listed on the window of your new car, what happens in the field is completely up to what you do with the material--your camera, your meter, your subjects, your metering style, your shutter speeds, and especially, your taste in negatives. Once you step outside of the ISO lab, you're on your own. :-)

-- Michael Darnton (mdarnton@hotmail.com), April 13, 2002.

I've always shot Tri-X at 250, by the way, for the extra shadow detail that I like. The general rule is that you can't go wrong overexposing neg films a bit, nor underexposing slide films a hair, but that the opposite is often fatal.

I took a workshop with David Vestal in about 1973 that changed the way I looked at film. He noted that though the zone system regards ten steps in a film's exposure range, the scale actually extends quite linearly in the over-exposure direction for three or four or five more stops, and that thick negs were perfectly printable, and gave fabulous shadow detail, especially with slight underdevelopment.

That's how I worked thereafter, and it's true, however now that I'm only scanning negs, not printing them on silver, those same dense negatives are deadly, and I'm thinking that I really need to get a better scanner with more range--in the meantime, my preferred neg is quite a bit thinner and flatter, and I work the shadows in Photoshop to get much the same look I used to get (but I'd never be able to make silver prints of today's negs as I used to do.)

Anyway, what I'm trying to say is that you have to tailor the totality of what you do to the results you like and your favored subject matter, and what you end up doing might not be what the film or developer directions say. For instance, for years I was doing archival documentation of violins and arrived at overdeveloping T-Max 400 in its own developer as giving the best results. I couldn't process my own film with it, however, because I just couldn't even begin to print the resulting negs with any joy.

-- Michael Darnton (mdarnton@hotmail.com), April 13, 2002.

I do not shoot b&w film other than Portra B&W, a C41 film. I rate Velvia EI 40 under most circumstances; EI 32 in high-contrast light, and ISO 50 under low-contrast (overcast) light. I shoot Provia 100F very rarely but rate it at EI 125 as with all ISO 100 reversal film.

-- Jay (infinitydt@aol.com), April 14, 2002.

In a Nikon FE2 or 8008, I can rate Velvia at 50. In a Leica R4 or M6, 40 is better. Similarly, for Provia 100F, 100 in a Nikon, but 80 is often better in the Leicas (not quite as critical as Velvia).

-- Bob Fleischman (RFXMAIL@prodigy.net), April 14, 2002.