Exposing Tri X and Normal Development Timesgreenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
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?
-- Deanna (DeannaNYC@aol.com), January 02, 1998
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.
-- jim megargee (firstname.lastname@example.org), January 02, 1998.
Jim, I have a question. Suppose you have a contrasty scene and you use your spot meter to get the reading from the shadow, but in your subsequent pictures you have a more evenly lit scene and you take the average meter readings. Now how do you develop such a roll? Will you then get some overdeveloped frames from which you may not get the best print? --Hasan
-- Hasan Ali (Hasan2@msn.com), January 04, 1998.
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 Brown (email@example.com), January 04, 1998.
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 megargee (firstname.lastname@example.org), January 05, 1998.
Overexposure adds density to highlight and shadows. Moderate overexposure does not necessarily add contrast, so development does not necessarily need to be reduced.
-- Tim Brown (email@example.com), January 08, 1998.
Tim I have not been on in awhile and have just read your response. Three things-- One-- overexposure (more than necessary) does change the contrast of a negative dispite popular belief. It effects the way in which the mid range is interperted by the film . Rather than a "smooth" translation, it causes a distortion in those areas. Second-My main point was that the use of the terms over and under expose actualy refer to the highlight of a negative not the shadows areas, as is commonly thought. Since shadows are used as the basis for exposure, these areas are (or should be) " normaly" exposed. Third- If a negative is given additional (more than is necessary) exposure to the shadow area. Chances are that the highlight area has also recieved more exposure than necessary by the same amount. Reducing the development will assist in pulling the "overexposed "highlight into a more printable range on a normal grade paper without having to burn in those areas. This assumes that the additional exposure to the shadows was done to raise those values above "average". Hope this clears up my point.
-- jim megargee (firstname.lastname@example.org), February 18, 1998.
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
-- Daniel Kaylin Jackman (email@example.com), February 18, 1998.