What factors affect grain?

Discussion in 'Exposure Discussion' started by sterioma, Nov 4, 2004.

  1. sterioma

    sterioma Member

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    I have just completed developing two rolls of Tri-X (35mm) + Rodinal. In both cases the E.I. has been 400. First time the dilution has been 1:50 (14 min), second time 1:25 (7min).

    I was expecting to see some less grain in the second roll (since developing time has been decreased), but I virtually couldn't see any difference. On the other hand, I can see a great variance in graininess amongst different pictures from the same roll, but I couldn't quite figure out what to attribute the difference to.

    I should add that I have assessed the grain by evaluating scans from the neg (at 3200 DPI) and trying to use the 50mm as a loupe to read the negative itself. Will bring the negatives to the lab soon to have some sample prints.


    So, given a film/developer combo, which are the factors that affect the graininess of the negative?

    Exposure?
    Developing time?
    Agitation?
    ...
    others?


    P.S. I've read that a sudden change in temperature between developer/stop-bath/fixer/wash can cause the grain to cluster, but I would exclude that since I carefully tested my temperatures throughout the process.
     
  2. clogz

    clogz Subscriber

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    Comments on the possible factors I will leave to the more technical minded people here. However, one thing is very important: subject matter. A picture with lots of highlights and middle greys will show more graininess.
    Hans
     
  3. TPPhotog

    TPPhotog Member

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    With 35mm the difference between the grain on Rodinal 1+25 and 1+50 is very very slight. I'd also go with Hans here on subject matter.

    The way I test (which is why I don't often) is shoot a whole roll of the same picture and chop up the roll to develop in different soups / dilutions.
     
  4. modafoto

    modafoto Subscriber

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    The more you underexpose and overdevelop the film, the more evident the grain will become. If you rate the film (Tri-X) at ISO 400 and develop for the suiting time it will be more grainy that if you rated it 320 or 250 (and develops for the suiting time).
    Also, if you agitate too much it will lead to overdevelopment and, therefore, also to more grain.
    Last I will comment on the use of Rodinal with Tri-X. This combo is GREAT, but it is a good thing to experiment with rating the film 250-320 instead of the 400 it says on the box. The reason is, that Rodinal decreases the speed a bit.

    Please correct me if I'm wrong, but this what I have been told and experienced.
     
  5. sparx

    sparx Member

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    I would have thought pushing the film would have more effect than different dev dilutions. Don't dilutions affect contrast more than grain?
     
  6. sparx

    sparx Member

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    Thankyou Morten for beating me to it :tongue:
     
  7. TPPhotog

    TPPhotog Member

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    Yep Pushing the film boosts the grain beautifully if that's what your after. But as both films where shot at the same speed it shouldn't be a factor here for the comparison. On some frames your errrrm exposure might be a bit off but I didn't want to mention that (where's the blushing emoticon on here?).
     
  8. sterioma

    sterioma Member

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    No need to blush :smile:

    I am here to learn and therefore if also an exposure problem is (perhaps) to be blamed, I need to know about it! :smile:

    Tonight I will try to post some sample from the scans, so that maybe the diffrerence in grain is easier to spot for you guys. I have found that resizing the scan removes most of the grain (and sharpness for that matter), so maybe I will post some small crop at 100%.
     
  9. ThomHarrop

    ThomHarrop Member

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    Another factor in grain is wet time. Overly long fixing or washing times can also cause migration of silver grains and add to clumping (which is what we see as excessive grain).
     
  10. Flotsam

    Flotsam Member

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    Years ago, I worked as a B&W printer in a Lab over in White Plains. One day the guy that processes the B&W film came into the printing room with a roll that was about as reticulated as any that I've ever seen. It was was first thing in the AM and in his pre-coffee condition, apparently didn't notice that his wash water was coming in at 150 degrees F. The effect was quite interesting,although not exactly what he client was going for. We gave him back his roll along with an admonishment not to leave his camera in his glove compartment on a sunny Summer day :wink:
     
  11. Nicole

    Nicole Member

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    Hi M, please help me understand the different effects again.
    If I use Tri-X 400 and expose at 320, do I ask the lab to process at 320 or at 400? In doing either, what effects can I expect?
    Thanks M!
     
  12. ann

    ann Subscriber

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    shooting at 320 should give you more shadow detail and i wouldn't tell the lab anything, this dfifference is very small, however if they are using kodak's numbers don't be surprised if they are over deveoped, it is a common issue at least in this area fir the labs to overdevelop ,which does increase the grain
     
  13. sterioma

    sterioma Member

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    I am finally home so I can post a couple of samples from the same roll (Tri-X at E.I. 400 and Rodinal 1:25 for 7 minutes). I have attached both the complete picture resized (and smoothed by the algorithm) and the detail from the scan at 3200 DPI.

    To me the difference in graininess is quite different. What do you guys think?

    Stefano
     

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  15. modafoto

    modafoto Subscriber

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    Don't tell them anything. It is just a third of a stop overexposure which is OK (if not better) with negative films (gives you more "information" on the film = shadows detail).
    Try doing a roll with exposures at 200, 250, 320 and 400, and write which frames have been exposed in which way. Then you can evaluate the negatives and see what kind of rating you like (at the given development the lab offers).

    Don't you have the possibilty of developing yourself. I will give total control and you'll save some money.

    Greetings Morten
     
    Last edited by a moderator: Nov 4, 2004
  16. Helen B

    Helen B Member

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    Please don't read the things you already know, or the bits where I'm talking rubbish.

    I think that it's quite difficult to compare graininess without controlling lots of things - including what you use to make the comparison. I guess that it's OK to use a scanner for comparison, if it is the scanner that will be used for final output. A lot will depend on the scanner - and particularly the interaction between the film granularity and the scanner resolution. Grain aliasing and all that.

    Contrast affects the appearance of grain, as does density. Therefore if you don't develop the two films to the same contrast, and compare areas of the same density (preferably of the same subject) then it's difficult to be objective. You may not wish to be objective, of course, and that's perfectly valid as well.

    Some extracts from the Communist Party (Marxist-Leninist) Manifesto:

    Overexposure increases graininess and decreases sharpness with conventional monochrome negative film, if the development time stays the same. Hence the saying: 'Expose just enough.'

    Overexposure decreases graininess with chomogenic B&W and colour negative film if the development time stays the same.

    Increasing developer dilution slightly increases graininess and sharpness (a very general, and dangerous, er, generalisation). The effect varies between developers, but in many cases the change is caused by the change in sulphite concentration: from a high sulphite environment (say 80 to 100 g/litre) to a low sulphite one (say less than 30 g/litre).

    Best,
    Helen
     
  17. modafoto

    modafoto Subscriber

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    Ok? I thought it was the rule for all of them...

    Thanks for expanding my knowledge!
     
  18. TPPhotog

    TPPhotog Member

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    Mmmmmm Stefano sorry not helping me I'm affraid :sad: I'd suggest you shoot a whole roll of one picture with no other variations. Cut a few frames off at a time (in darkness of course) and try souping each length in different dilutions. That way you will be able to compare the results without any other distractions.
     
  19. sterioma

    sterioma Member

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    Helen, thanks for your comments.

    I haven't got the space and money and the time to learn to do my own prints right now, hopefully this will be an option next year. In the mean time, as I mentioned before, I am using the scanner to evaluate the negatives I am producing (I have just developed 3 rolls so far!). I guess I will need to invest in a loupe. As far as the prints are concerned, I am evaluating trying both to have the prints from the scan and from the negatives (by a lab), and decide what I like better (and what's cheaper).


    Actually the samples I have posted are from the same roll. I was experiencing a different grain across the different frames, so that's the reason of my post.
     
  20. Helen B

    Helen B Member

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    Oh, I told you not to read the bits where I was talking rubbish...

    I did realise that they were from the same roll - but perhaps didn't make the differences between specifics and generalities clear enough. This is the root cause of all human conflict, I believe. Were the two frames scanned with exactly the same settings? (Is the software doing something behind your back, out of your control?) How does the local contrast differ in the two examples? How does the density differ? These are the kind of questions to ask yourself, I guess.

    The local contrast, density change and overall density will affect, to some degree or another, the exact way in which the developer works grain-by-grain. The more agitation, the less the effect, in general.

    I've got nothing against scanners (and you don't need to justify using one) but some of them do behave oddly when they are dealing with opaque grains/grain clumps when the grain 'size' is in the same ball-park as the scanner resolution. Just another influencing factor.

    Best,
    Helen
     
  21. Woolliscroft

    Woolliscroft Member

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    That's true, especially if you have anti dust/scratch software running as it can knock out small gaps between grains by interpreting them as dust spots. However, is there really that much difference in the grain between the shots you posted? One shows a lot of detail, the other large areas of mid tone. Grain always tends to be more visible in the latter than the former even though objectively the same size. I never did much like Tri-X because of the grain, although I am having to use it now since Delta 400 vanished in 220. If you don't like it but need the speed you can always use Delta or Tmax.

    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.
     
  22. mikewhi

    mikewhi Restricted Access

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    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'. :D
    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
     
  23. bjorke

    bjorke Member

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

    Helen B Member

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    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
     
  25. Tach

    Tach Member

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    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
     
  26. Helen B

    Helen B Member

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    ... 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