I am looking for a table of approximate reciprocity correction for B&W films. The one I have is from an old and very tattered Kodak publication, and has a nifty graph to go along with it.
I cannot find it at Kodak's web site, or on the web, although there are many references to general reciprocity correction information. Do any APUGers know where I might find this table/info?
The problem I have with these tables is that they imply that the entire film goes into reciprocity failure at once. Generally this is not the case. In general, only the shadow areas of the image are in reciprocity failure while the rest of the image is fine. In the shadows the film isn't seeing enough photons to create a latent image -- it's more of a threshold failure.
What the tables teach you is to increase exposure. You have to do this so that the shadows see enough photons to cross the threshold and create a latent image. Of course areas of the film that are not in reciprocity failure get the same increase in exposure and are therefore over exposed. Thus the recommendation to decrease development time -- to try to keep the highlights from getting too dense.
The reality is that reciprocity tables are an attempt to offer a one-size-fits-all solution to a problem with a huge range of "sizes" if you will. With roll film this may perhaps be a reasonable compromise, IDK. With sheet film the answer is to think about what you are doing and treat each film individually.
Also, I suspect that for each individual film stock, processing for reciprocity failure may depend on workflow -- particularly on developer choice and agitation style. But I've never made the effort myself to chart this, nor have I found any such research by others.
I'm just sayin' that the tables are a very rough place to start and that you'll likely have to do a fair amount of tuning to get results you are pleased with.