Essentially they are the same film emulsion so the grain that is produced on film will be appoximately the same structure and size regardless of film format. It is the enlargement factor which makes a difference when the film grain is enlarged enough to make a visible difference in the print.
Ultra fine grained film developed in specific developers will show no grain until you get to really BIG enlargement factors. But it's not only the grain itself, it is the acutance of the grain clumps which have localised edge effects which make an image look sharper and at the same time enhance the visibility of grain clumps in the print. So its swings and roundabouts. You have to find a happy medium which suits your personal aesthetic. Ultrafine grain in film can make a print look lifeless as it usually has little acutance.
Developers like rodinal can create much higher acutance grain whereas a developer like perceptol will create very fine grain but with less acutance. Standard developers like ID11/D76 are in the middle and have an optimal balance between grain clump size and acutance.
As always YMMV. some people prefer more acutance and some people less and some in the middle. Take your pick.
The standard is rooted in print quality. Huge amounts of research went into it. These studies sought to formalize the relationships between objective and subjective print characteristics and formed the basis for the current standard. Obviously this research is not in the current standard itself since the standard is concerned with specifying the speed measurement criteria...
...The people weaseling are those who claim ISO speeds are for laboratories and have no practical relationship with fine art prints, or that ISO speeds are marketing gimmicks, misleading, incorrect etc.
Introduction
...
This International Standard recognizes that black-and-white films do not generally have a unique speed if several different processes are recommended. This conflicts with the tradition of associating a specific speed value with a particular product. In the future, the process used for determining speed values should be unequivocally described to avoid misinterpretation. Since users often do not know how these films will be processed, manufacturers have an obligation to provide a speed value for this situation which will ensure good results.
...
7. Product marking and labelling
..., since the speed is dependent on the illuminant, exposure time and process used, these conditions should be clearly indicated whenever practical when quoting values to avoid misinterpretation.
Do 35 and 120 of the same film differ in grain ?
For example Ilford Delta 400 in 35mm shows more grain than Ilford Delta 400 in 120 ?
I was just giving an example to ask if there are any differences by format. I do use 100 film too and in some cases push 400 to 1600 as wellAs the neg is bigger, it needs less enlargement to get the same sized print.
Why would you use high-speed film in a search for fine-grain? Use Delta100! (And don't forget that fine-grain, sharpness, density and contrast all play off each other and all affect the viewers perception of the print).
Your assertion "Most films box speed is not realistic and is almost always the highest possible, hence most folks shoot at half the box speed by default" is a perfect example of the weasel words referred to earlier, and has no factual basis. The statement is also incorrect/unclear as to why "most folks shoot at half the box speed by default". The vast majority of people who do this, do it either because they've used a Zone System type of test to establish an EI, or because they've been told to do it (ie it is a tradition). It has little to do with print quality. You said it yourself: They do it by default.
So, it must be said that the situation is really quite the opposite of that often described. People have this idea ISO speeds are fictitious and that their EIs give them better results. The reverse is actually the case. ISO speeds have a sound basis, while the vast majority of people claiming their EIs are the "real" film speeds have no idea what they are talking about, and aren't making the negatives they think they are making.
"Most films box speed is not realistic and is almost always the highest possible, hence most folks shoot at half the box speed by default" is a perfect example of the weasel words referred to earlier, and has no factual basis.
How? The only way in which it is "loose" concerns the developer, which is no longer a specified formula. In some ways this is a good thing, since ISO should be achievable using a general purpose, commercially available developer. Kodak indicates in its publications that TMax 100 (for example) has an ISO speed of 100 in most developers.
Without grain, how do we achieve shades of gray? AKA tonality.
There were a few changes to the standard including developer/development and hold time, but the criteria remained the same. There is nothing loose, and Kodak clearly states in its tech pubs (including TMax 100/400) that they are ISO xxx films, and that these speeds were determined as specified in the standard (and it will work in most developers). Ilford similarly specifies the film speeds are ISO ratings, and reserves EI for the ranges within which the films can be expected to produce good results.
There is no "big divergence" between "box speed" and "actual EI" when it comes to either TMax 100 or 400 developed in a standard developer such as ID-11/D-76, and using expressions such as "actual EI" is simply misleading. It perpetuates the myth that ISO speed is not the actual speed of the film, and that some sort of hidden truth is to be discovered by running a more arbitrary personal EI test. The divergence between that sort of test and ISO is simply a matter of methodology, and reveals nothing but the differences between the two tests. Unfortunately the "experience of a great many photographers" means little, and is not evidence of anything. It's a combination of seeing what you want to see, being influenced by others, using a Zone System EI test, and a lack of understanding of film speed/tone reproduction. All this leads to people making erroneous claims and spreading nonsense about ISO conspiracies.
It's the lack of apparent grain, or keeping it as small as possible that the thread is about.
Ian
I think people should use whatever EI they want, but they should also refrain from spreading nonsense about the standard being a marketing gimmick, or using Zone System EIs (which are lower by a predictable amount) to substantiate their claims that ISO speeds are wrong.
There were a few changes to the standard including developer/development and hold time, but the criteria remained the same. There is nothing loose, and Kodak clearly states in its tech pubs (including TMax 100/400) that they are ISO xxx films, and that these speeds were determined as specified in the standard ...
Michael, Kodak uses EI 100/400 for TMax; there is absolutely no mention in the tech pub for Tmax that these films are ISO xxx films.
...and EI is not ISO.
Perhaps, you've been misled by: determined in a manner published in ISO standards..
http://www.kodak.com/global/en/professional/support/techPubs/f4016/f4016.pdf
Here is something to loosen up a bit more.
Typically the EI speed is about one stop lower than ASA or ISO.
http://motion.kodak.com/motion/uplo...nce_Guide/kodak_essential_reference_guide.pdf
ISO vs EI Speed Ratings for KODAK Films http://www.kodak.com/global/en/professional/support/techPubs/cis185/cis185.pdf
A bit confusing, isn't it?
Suggest you go back and actually take the trouble to read the T-Max link you posted so that you have a clue what you're talking about.
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