What factors affect grain?

[mikewhi]

OK, Let's see if people can agree on these rules as a start to keep graininess down:

1) Overdevelopment increases grain.
2) Overexposure combined with overdevelopment will give you even more grain.
3) Underexposure and overdevelopment will give you grain in the dense areas and not in the thin (underexposed) areas.
4) Expose your negatives 'just enough' to give you adequate detail in the shadows - no more and no less. In Zone terms, this is Zone III.
5) Develop your negs 'just enough' so that they don't build up too much density and thus too much grain. 'Just enough' is a density such that you can just read newprint thru it in a sunny room. You should not be able to read the print too easily, but it should be readable not just discernable.
6) Keep wet time to the minimum for processing.
7) Keep temps consistent to avoid reticulation.
8) Avoid taking picutres of wood as it's by nature 'grainy'.
9) Since a really thin negative has little or no grain, and a really dense one has lots of it, there must be some correlation - eh?

Also, this idea of rating film at varaious ASA's and pushing and pulling processing are really terms that show a lack of the basic concepts of sensitometry. I am not putting anyone down, so please don't throw rocks at your monitor. I simply mean that for your camera\film\dev there is one and only one correct ASA speed. By the definitions of ASA (American Standards Assoc), the ASA speed is that which produces .1 above film base+fog. There is only one ASA speed that can do that, and your mission, if you choose to accept is to find that speed. If caught, Ansel Adams will disavow any knowledge of your actions.

So, I'd recommend sticking with the rated ASA. All it means to rate it at 320 is to give 1/3rd stop more exposure. That's it. Pushing and pulling processing just mean changing the develpment times to compensate for exposure times so that you either build up or contract densities to stay in the ranges that I gave in steps 4 & 5. These terms are mostly used by people who don't own a densitometer (are there actually such people out there? do they secretely whish they had one?), don't understand or care about sensitometry. In short, they're interested in what they can get on the negative which is what it's all about, Alfie. The ZS and sensitometry make a system out of it so it is reliable, repeatable and predictable. How many people do you know who 'push' the film 3 stops, have it push processed and 'hope' that it comes out? If they knew the ZS and sensitometry, they'd know in advance. OK, enough preaching - wine induced I promise you all!!

Does that sum up the reasons for grain, folks? I'd say if different frames showed different levels of graininess then it directly relates to the exposure, development and processing practices employed.

-Mike

[bjorke]

...if you have anti dust/scratch software running as it can knock out small gaps between grains by interpreting them as dust spots.

Digital ICE etc, do not function on B&W films like Tri-X. XP-2, yes. FP4, no.

[Helen B]

David asked 'Incidentally, I notice that the Pro medium format version of Tri-X is rated at 320. Is it the same emulsion or is it really a bit slower?'

David,
320TXP is a different emulsion, with different characteristics, especially in the darker tones - it has lower contrast in the shadows than the midtones and highlights which gives smooth shadow detail that seems to go on for ever, good midtones and bright highlights. Because of that it's a film that responds to careful midtone placement more than other films. 400TX is more of a standard straight-line sort of a film. I'd say that 320TXP doesn't push nearly as well as 400TX.

Mike,
I'm not sure what you are getting at. Nobody but you has referred to ASA in this thread - the only reference to a standard speed has been ISO 400 for Tri-X, which is what Kodak themselves say on the 400TX box. All other references are to an EI or to a simple number. What's wrong with that?

Best,
Helen

[Tach]

Also, this idea of rating film at varaious ASA's and pushing and pulling processing are really terms that show a lack of the basic concepts of sensitometry. I am not putting anyone down, so please don't throw rocks at your monitor. I simply mean that for your camera\film\dev there is one and only one correct ASA speed. By the definitions of ASA (American Standards Assoc), the ASA speed is that which produces .1 above film base+fog. There is only one ASA speed that can do that, and your mission, if you choose to accept is to find that speed. If caught, Ansel Adams will disavow any knowledge of your actions.

-Mike

Mmh... that's why I call it an EI (exposure index). Make it a PEI -personal exposure index-, if you wish.

There are many ASA speeds possible that produce .1 above base fog; just make development time variable. This will push up the characteristic film curve, maximally in the highlights, less in the medium tones, and minimally (but noticeably) in the shadows. In other word, development time affects negative contrast and speed.

There are many other variables, other than development time, than affect film speed. As an example, consider the color temperature of the light used in the exposure (daylight, tungsten or ?), the agitation method and time (continuous, intermitent every 30 secs, every 60 secs, stand development?) , and which developer (rodinal, microphen, others?) was used to process the film

ASA just standarizes those variables, using daylight as light temperature, using a standard agitantion method, using a specifically determined developer, and developing as long as it takes to reach a contrast index of 0.62.

After that, and reaching an tentative speed, it multiplies it by 0.8, to help prevent people underexposing by claiming film is 20% slower than it really is.

My point is that ASA speed is a (very?) good approximation of the film speed, but unless you develop it exactly as specified in the standard, there are no guarantees that YOUR speed, with your developer, agitation method, contrast preference or whatever, will be the same.

Saludos, Santiago

[Helen B]

... and toe speed is not the only practically useful or commonly used (as opposed to International Standard) way of choosing the number to set on your exposure meter (NTSOYEM, or can we call it EI for short?).

Best,
Helen

[Ed Sukach]

It's interesting how tenacious some things are in photography. "ASA" - the American Standards Association is no more - it was replaced by "ANSI" - the American National Standards Institute", some time around 1970 - 1973 ~ 30 years ago, or so.
ANSI, itself is no more - everything went to ISO - not sure of the acronym, but something like "International Standards Organization" .. some time in the early '90's
Interesting - how we cling to "ASA". The only place I see it mentioned now is in reference to film speed. It is correctly, "ISO"... lest someone starting out become confused.

[John Koehrer]

Yes, and ISO is the manufacturers recommended/tested speed under very tightly controlled circumstances. EI(exposure index) is what the individual needs to determine for their own specific circumstances. When you change developer/meter/camera/etc. you also need to retest to determine the new EI(PEI)

[rogueish]

Ei EI Ei O ?
Sorry couldn't resist...

[Helen B]

'ANSI, itself is no more'

ANSI still exists, and it is responsible for a number of photographic ISOs, including the ones on the required purity of chemicals for photo use. It is reassuring to know that the purity of our vital fluids is controlled by the free world.

Best,
Helen

[djklmnop]

Be sure to do testing with Tri-X!!! I used to shoot Tri-x at 250 but when i finally got around to doing real testing, Zone I landed on ISO 160 !!! This was confirmed by my mentor as well - "yes, I thought I'd let you figure that out for yourself" was his response (bastard! hehe). But then again, Tri-X was never "fine grain" to begin with. And is very prone to reticulation. TMax films are more resistant to reticulation. As for developer effecting Exposure Index, for normal development you should only get ONE exposure index in accordance to your combination of equipment, developer, dilution choice. When you do an N+1 then sure, you'll get a 1/3 stop change in EI for the increased density - so rate it 1/3 stops faster. For practical use, agitation method will not change your EI significantly enough to scream bloody murder. Developer dilution will though! The higher the dilution, the higher the compensating development occurs thus lowering ISO speed.

And yes, Mike is right.. If you don't do the proper testing, all it is is guesswork.

Attached are some Tri-X from 35mm.