Exposing Tri X and Normal Development Times

Let me see if i can explain this. Ok, so for more shadow details one can expose tri-x at 200 or lower? Ok, but do development times change from the normal times too, or is there a formula (exposure vs. development times)for each film?

Exposing tri-x at 200 iso will not auotmaticly give you more shadow detail. As with any ISO that you use ,the amount of shadow detail you achieve will depend upon "where" you have taken the exposure reading from in the scene. An extreme example would be if you pointed your meter at a light scource in the scene and used that exposure, it would not matter if you were using 200 or 50 ISO. Chances are you would have little or weak shadow detail. IMHO its always best to use the given ISO of the film and expose correctly rather than depend on trying to convince the film that it has an ISO that it doesnt. Unless of course you are forced to work under extreme conditions.

But if you are using 200, you should underdevelop the film by an equal amount. Start with 20-30% of your normal time and then adjust to the type of neg you prefer.

Tri-X has enough exposure latitude to expose it 1-2 stops more than the minimum amount (you find this by testing) of exposure that gives decent shadow detail without changing development time. Cutting development time 20-30% will give a flat negative even if it's overexposed a stop.

Tim - It should be understood that over/under exposure refers to the highlight of a scene , not the shadow, as I'm sure you know. If you are using an averageing meter and an ISO of 200 with a 400 ISO film, then you are (on average) overexposing the film by one stop with each exposure, creating a highlight of greater density than necessary. Pulling back on development will assist in producing a more "normal" negative.

Jim,

 

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Overexposure adds density to highlight and shadows. Moderate overexposure does not necessarily add contrast, so development does not necessarily need to be reduced.

There is no such thing as over or under exposure. There is correct exposure which places the shadows where you want them. Then there is plus and minus development to place the highlights where you want them.

What you are refering to i believe is what film speed you should use. This is determined by a number of things , such as 1. your paper 2. your type of enlarger 3. your camera and meter. I am taking forgranted that you are using a roll film camera. Expose your film in this manor using tri-x ... first frame no exposure second frame four stops under exposed at iso 200 and repeat this exposure sequince at iso 250, then again at iso 320 and 400. Then print an unexposed neg. till you just get a full black an the paper you use, and with the enlarger you will most often use. then print the exposed frames with out changing anything, and wich ever one of these negs. gives you the first noticable change in gradation will be the correct iso for you.

Dan