Box ISO rate and Real ISO

Discussion in 'B&W: Film, Paper, Chemistry' started by marciofs, Apr 28, 2014.

  1. marciofs

    marciofs Member

    Messages:
    697
    Joined:
    Jul 8, 2011
    Location:
    Hamburg
    Shooter:
    Medium Format
    Hi,

    So, I shot and develop a roll of 35mm Fomapan 400 with Rodinal following the data in digitaltrhth.com.
    But later on I founded out the real ISO of fomapan 400 is 250 with Rodinal.
    So I wonder of the data in digitaltruth.com, dispite it says ISO 400, is indicating the development time for its real ISO which is 250?

    I god a good result from development but I usually over expose a bit.
     
  2. AgX

    AgX Member

    Messages:
    11,592
    Joined:
    Apr 5, 2007
    Location:
    Germany
    Shooter:
    Multi Format
    The "real" ISO speed with Rodinal would mean applying ISO standards on estimating the film speed of this combo.
     
  3. Ian Grant

    Ian Grant Subscriber

    Messages:
    17,933
    Joined:
    Aug 2, 2004
    Location:
    West Midland
    Shooter:
    Multi Format
    You really mean your personal EI (exposure index). I don't use the 400 but do use the 100 & 200 both at half the box speed with great results.

    Ian
     
  4. michael_r

    michael_r Subscriber

    Messages:
    6,438
    Joined:
    Feb 2, 2010
    Location:
    Montreal, Canada
    Shooter:
    Multi Format
    Marciofs,

    A film has only one ISO speed based on a set of strict criteria. If this film is ISO 400, that is its speed under ISO test conditions. However once you depart from those conditions, the effective working speed, usually defined as Exposure Index (EI), may or may not change. Some of the factors are objective (perhaps Rodinal does not yield full ISO speed), and others are subjective.

    Here is a good summary from Kodak. It will apply to any film.

    http://www.kodak.com/global/en/professional/support/techPubs/cis185/cis185.pdf
     
  5. markbarendt

    markbarendt Subscriber

    Messages:
    7,250
    Joined:
    May 18, 2008
    Location:
    Beaverton, OR
    Shooter:
    Multi Format
    The ISO rating of a film is done per ISO specs by the manufacturer. Probably not done with Rodinal.

    If you follow the manufacture's instructions and use the same developer, agitation, temperature.... then you should find the speed very close to what the manufacturer found.

    If you do anything else it's no longer going to match the ISO and the new number is better referred to as EI or exposure index.

    Your EI is "personal" and reflects your processes, biases, metering practices, your equipment's vaugarities, the quality of water used, and more.

    Finding an EI other than box speed and different than others find, that works good for you for any given combo of equipment and materials, is perfectly normal.
     
    Last edited by a moderator: Apr 28, 2014
  6. michael_r

    michael_r Subscriber

    Messages:
    6,438
    Joined:
    Feb 2, 2010
    Location:
    Montreal, Canada
    Shooter:
    Multi Format
    Correct. The developer is specified in the standards. It is not related to Rodinal.

    We should also mention although unlikely, Rodinal may or may not produce a curve with this film which meets the standards for ISO 400. A recommended EI on digitaltruth could still be any other number.
     
  7. Alex Muir

    Alex Muir Member

    Messages:
    406
    Joined:
    Dec 23, 2009
    Location:
    Glasgow, Scotland
    Shooter:
    Medium Format
    I have also wondered about whether or not to use the 'box speed' development time quoted in guides like Digital Truth for the EI I have calculated. I have normally done that and then adjusted the development time, if necessary, for future films. I think the quoted time for a particular film/dev combination at 'box speed' generally comes from the manufacturer of the film or developer.
    If you got good results with the method you tried, I would stick with that speed and time.
    Alex
     
  8. Gerald C Koch

    Gerald C Koch Member

    Messages:
    5,945
    Joined:
    Jul 12, 2010
    Location:
    Southern USA
    Shooter:
    Multi Format
    Usually a film manufacturer will give developing times and film speeds for a variety of developers. The more common developer information is usually included as an insert or printed on the box. Don't use Foma film so this may not be the case for them. Developer manufacturers provide similar information. I usually take information given by third-party sites with a certain amount of scepticism.
     
    Last edited by a moderator: Apr 28, 2014
  9. marciofs

    marciofs Member

    Messages:
    697
    Joined:
    Jul 8, 2011
    Location:
    Hamburg
    Shooter:
    Medium Format
    I am saying that because wherever review I find in the internet they say Fomapan 400 is actually ISO (or better perfomaced) at 250 to 320 depending on the developer (250 for Rodinal). And I have read many posts complaining about issues with this film exposure and replies explaining it is because 400 is not the real ISO.

    After reading that (in different pages) I was surprised I got a good exposure. And I was wondering if the data in digital truth is actually adapted to develop it at ISO 250, or if it was because I am used to over expose a bit so I just got luck.

    This is a example of what I got: http://www.marciofaustino.com/uploads/1/6/4/6/16464874/9508865_orig.jpg
     
  10. Bill Burk

    Bill Burk Subscriber

    Messages:
    4,892
    Joined:
    Feb 9, 2010
    Shooter:
    4x5 Format
    Possibly your shutter is "slow" which allows you to get good results using EI 400 settings, even if processing in Rodinal might give you an actual film speed closer to 250.
     
  11. marciofs

    marciofs Member

    Messages:
    697
    Joined:
    Jul 8, 2011
    Location:
    Hamburg
    Shooter:
    Medium Format
    I will try with an other camera then..
     
  12. Xmas

    Xmas Member

    Messages:
    6,419
    Joined:
    Sep 4, 2006
    Location:
    UK
    Shooter:
    35mm RF
    The real ISO is in the manufacturers data sheet for Formapan 400, the box speed in marketing hype to a degree.
    The Formapan 100 data sheet also seems accurate, not tried Formapan 200 much.

    Forma have provided the contrast, fog and ISO dependency for time and temp for three developers.

    google
    formapan 400 datasheet

    Then you need an adjustment for your developer, meter/shutter and metering technique.
    Digital truth is closer to 'Analogue Porkies'

    Rodinal @ 20C 1+100 stand will be in the 250-320 range with low contrast, but you may not like the rendering, I set my Weston to 250. Pour in the Rodinal invert a few times and set the kitchen timer for 60 minutes. Id also temper the following solutions to 1C, cause the Forma is not as prehardened as Kodak or Ilford film.

    Most of my shooting is high contrast.

    Noel
     
  13. TimFox

    TimFox Member

    Messages:
    102
    Joined:
    Jul 21, 2009
    Location:
    Chicago
    Shooter:
    Large Format
    The actual ISO speed (formerly ASA) is a property of the film only. If you go to the actual ISO specification document, the number is based on exposure at the "toe" of a negative film, where it first starts to show density above the base level. The development details will affect strongly the slope of the curve above the toe, and therefore the exposure required to reach the standard 18% density grey level. Still the best description of how to rate film speed for specific applications can be found in Ansel Adams works on the Zone System.
     
  14. Sponsored Ad
  15. momus

    momus Member

    Messages:
    2,429
    Joined:
    Jun 14, 2009
    Location:
    Lower Earth
    Shooter:
    Medium Format
    With that film, anything is possible. I was shooting Arista EDU 100 at the box speed and getting terrible results. Found out later that the film is actually Fomapan, and that I needed to shoot it at ISO 50. When I did that it looked much, much better. Tri-X is another film that seems to not be rated correctly by the maker, as pretty much everyone will tell you that it is really a 200-250 ISO film, and my tests say just that. Of course, it being Tri-X, you can shoot it all over the place and get great results.

    The maker of the film gives you what they consider to be the correct ISO, but what developer you use, how you meter the shots, how you print the negs, etc will determine YOUR optimal ISO. There really is no other way to do it except to shoot a test roll. What I consider to be the optimal ISO is not what someone else agrees with, nor should it be.

    I shot a roll of Tri-X yesterday w/ my FT QL using a yellow filter, and metered it w/ a hand held meter at ISO 125. Then developed it normally. The shots came out perfect. On my NiKon N8008s and using the same yellow filter, I set the camera's TTL meter to ISO 320. These values came about by shooting test rolls and noting the results, and they differ from one camera to another. A dull, cloudy day will also require something different from a bright sunny day. Sometimes I shoot Tri-X at ISO 50 w/ a yellow filter because I personally like that sort of look sometimes. So it just depends on what you want on the finished end. Everything is done to suit my eyes, not anyone else.
     
    Last edited by a moderator: Apr 28, 2014
  16. michael_r

    michael_r Subscriber

    Messages:
    6,438
    Joined:
    Feb 2, 2010
    Location:
    Montreal, Canada
    Shooter:
    Multi Format
    The ISO speed point is determined based on a set of criteria when the film is exposed and developed under a specific set of conditions. The ISO speed point is for a fixed density of 0.1 above B+F such that the density increases by 0.8 at an exposure 1.3 log H higher than the speed point. This is what is commonly referred to as the "ISO triangle". Therefore development and a gradient are part of the standard. The Zone System is a related but different methodology, not necessarily a "better" one.
     
  17. momus

    momus Member

    Messages:
    2,429
    Joined:
    Jun 14, 2009
    Location:
    Lower Earth
    Shooter:
    Medium Format
    Well, too many angels on the point of this pin. Just shoot a test roll or two under controlled conditions using different ISO settings, take careful notes, develop consistently, and you're there.
     
  18. marciofs

    marciofs Member

    Messages:
    697
    Joined:
    Jul 8, 2011
    Location:
    Hamburg
    Shooter:
    Medium Format
    Yeah I will do that just for curiosity, because I like what I got anyway.
     
  19. c6h6o3

    c6h6o3 Member

    Messages:
    3,219
    Joined:
    Oct 16, 2002
    Shooter:
    Large Format
    Amen. The correct film speed is what gives you sufficient shadow detail. I rate my HP5+ at 100.
     
  20. cliveh

    cliveh Subscriber

    Messages:
    4,625
    Joined:
    Oct 9, 2010
    Shooter:
    35mm RF
    Shoot at box speed and develop to your own requirements.
     
  21. markbarendt

    markbarendt Subscriber

    Messages:
    7,250
    Joined:
    May 18, 2008
    Location:
    Beaverton, OR
    Shooter:
    Multi Format
    Just for giggles can we have some context for that rating.

    Developer?
    In comparison to manufacture's specs are you using minus development, stand...?
    Are you "zoning"? If so details?
    Subject matter?
    Spot meter or incident?
    Are you using old Petzvals or newish multicoated lenses?
    Is part of that rating a safety factor?

    My intent here is not to put you on the spot c6h6o3, but to help marciofs understand how you made your choice and at least some of considerations that go into the decision.
     
  22. michael_r

    michael_r Subscriber

    Messages:
    6,438
    Joined:
    Feb 2, 2010
    Location:
    Montreal, Canada
    Shooter:
    Multi Format
    His handle is the molecular formula for Pyrogallol. I'm gonna guess ABC. That's one stop. Zones, that's another 2/3 stop. Close enough. :whistling:
     
  23. markbarendt

    markbarendt Subscriber

    Messages:
    7,250
    Joined:
    May 18, 2008
    Location:
    Beaverton, OR
    Shooter:
    Multi Format
    :D
     
  24. Sirius Glass

    Sirius Glass Subscriber

    Messages:
    20,452
    Joined:
    Jan 18, 2007
    Location:
    Southern California
    Shooter:
    Multi Format
    +1
     
  25. Doremus Scudder

    Doremus Scudder Member

    Messages:
    1,240
    Joined:
    Sep 10, 2002
    Location:
    Oregon and Austria
    Shooter:
    4x5 Format
    Some here still haven't figured out that ISO testing is based on one particular development regime using a standard developer and a contrast index that likely does not relate to either of those things for most of us. ISO speed is similar to EPA mileage estimates for new cars: a good basis of comparison but your mileage may vary.

    The issue is further clouded by the practice of some manufacturers to label the film at a different "Box Speed" than the ISO speed. I find this deceptive and poor marketing in the long-term, since many will simply have poor results since their expectations have been falsely raised.

    Personal EI is based on the amount of shadow detail that each individual photographer finds necessary/acceptable for the kind of work s/he is doing. This includes personal and artistic decisions regarding developer, contrast, etc., etc. This includes all kinds of "pushing" and Zone Systems, etc., etc.

    Kodak's old recommendations still hold: If your negatives have too little shadow detail, increase the effective film speed. Too much shadow detail (i.e., more than you need)? You are overexposing and can get away with less, thus giving you faster shutter speeds/smaller apertures.

    Overall contrast is similar: Consistently too contrasty? Reduce development time. To flat? Increase. Plus, learn to base development on scene contrast.

    Best,

    Doremus
     
  26. Ian Grant

    Ian Grant Subscriber

    Messages:
    17,933
    Joined:
    Aug 2, 2004
    Location:
    West Midland
    Shooter:
    Multi Format
    Other way round you mean increase the exposure by decreasing the Effective film speed (EI - exposure index) - to give better shadow detail.

    Ian