Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,285   Posts: 1,535,262   Online: 940
      
Results 1 to 7 of 7
  1. #1

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,622

    Film speed rating

    For some of the less experienced out there (or experienced - doesn't matter), I thought I'd throw out this diagram I had done for myself back when I started learning about this stuff.

    2 hypothetical films given identical exposure to a calibrated step tablet and processed identically.

    Which is "faster", or which would you give a higher EI, etc.

    Enjoy
    Attached Thumbnails Attached Thumbnails Untitled.jpg  

  2. #2
    pentaxpete's Avatar
    Join Date
    Sep 2010
    Location
    Brentwood, Essex, England
    Shooter
    Multi Format
    Posts
    159
    Images
    78
    I think the RED one ?
    An 'Old Dog still learning New Tricks !

  3. #3

    Join Date
    Jun 2012
    Location
    UK
    Shooter
    Multi Format
    Posts
    1,285
    I've read a lot this year about films and slopes and chemistry and whatnot, and I still know almost as little as when I started. But I'll have a go.

    Am I right in thinking that as the two curves intersect at 0.1 density (which I think = base fog?) then anything to the LHS can be disregarded, and we have to look at the shape/slope of the curves to the RHS of that point?

    In which case the blue line appears to gain density at a greater rate with exposure, which makes me think it denotes the "faster" film.

    Now I shall be happy to wait and be shot down in flames ... well, I hope not internet-style flames ...

    EDIT hmm have I forgotten to take inertia into account? damn

  4. #4
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,680
    Blog Entries
    3
    Images
    19
    Looks to me like the red one would gather the most total shadow detail based on the exposure. But my guess is that because of the slope they might be both ISO rated the same.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

  5. #5
    baachitraka's Avatar
    Join Date
    Apr 2011
    Location
    Bremen, Germany.
    Shooter
    Multi Format
    Posts
    1,327
    Blue: Happy mid-tones.
    OM-1n: Do I need to own a Leica?
    Rolleicord Va: Humble.
    Holga 120GFN: Amazingly simple yet it produces outstanding negatives to print.

  6. #6

    Join Date
    Feb 2010
    Location
    Montreal, Canada
    Shooter
    Multi Format
    Posts
    4,622
    It's sort of a trick question but sort of not, because EI might be a personal preference vs ISO which has a defined set of criteria. So Mark is correct - based on the information on the chart (and assuming they were both given identical processing treatment to ISO standards, these both have the same ISO speed.

    pdeeh: Fog is out of the equation since the y-axis is showing net density (ie density above film base+fog).

    But there is then the matter of "personal EI". Different people might say different things. From a Zone System perspective, someone targeting 0.1 above fb+fog as a speed point 4 stops below metered might find the "red" film faster.

    Regarding mid-tones, one would have to extrapolate since the graph does not extend far enough to the right. But the far right of this graph is only 4 1/3 stops from the exposure where both films have a net density of 0.1. So the red film might actually have "happier" mid tones because contrast is higher in the midtones vs the blue film.

    Just some things to think about.

  7. #7
    markbarendt's Avatar
    Join Date
    May 2008
    Location
    Ignacio, CO, USA
    Shooter
    Multi Format
    Posts
    5,680
    Blog Entries
    3
    Images
    19
    It's a good trick question.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin