Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,502   Posts: 1,543,400   Online: 723
      
Page 1 of 4 1234 LastLast
Results 1 to 10 of 38
  1. #1

    Join Date
    May 2010
    Shooter
    35mm
    Posts
    26

    Ansel Adams Exposure Formula?

    So in p.66 of Book II, Ansel Adams outlines his exposure formula:

    Square root of your ASA give you the key stop
    Take your meter reading in c/ft^2 (foot-candles) and the inverse is the shutter speed at the key stop.

    So if shooting ASA100, the key stop would be f/10. And if luminance value is 100FC, then the exposure is 1/100.

    I'm trying to get this to work with my Sekonic 758C. I'm not coming in close. At f/10 and 100FC with ASA 100, my exposure reading is 1/8 second. Even taking into account a K factor, this is orders of magnitudes off.
    What am i doing wrong?

  2. #2
    Mustafa Umut Sarac's Avatar
    Join Date
    Oct 2006
    Location
    İstanbul - Türkiye
    Shooter
    35mm RF
    Posts
    3,837
    Images
    108
    I have no idea but may be he writes in metric terms ? Did you check for it ?

  3. #3

    Join Date
    May 2010
    Shooter
    35mm
    Posts
    26
    Yes. Definitely foot candles, not meter candles.

  4. #4
    MaximusM3's Avatar
    Join Date
    Jul 2010
    Location
    NY
    Shooter
    35mm RF
    Posts
    756
    Images
    7
    Just out of curiosity, as I have no idea of how this formula work, what would be the advantage of this versus taking a simple incident meter reading? Of course, it sounds like it could be valuable if one doesn't happen to have a meter and, like Ansel, be able to guesstimate luminance values.

  5. #5

    Join Date
    May 2010
    Shooter
    35mm
    Posts
    26
    I find it useful to be able to work in a luminance value as it is easier to figure out contrasts then go think about exposure after that. And you would still need a meter for a luminance reading.
    Last edited by davidave; 06-07-2011 at 08:23 AM. Click to view previous post history.

  6. #6
    Christopher Walrath's Avatar
    Join Date
    Dec 2005
    Location
    Milton, DE, USA
    Shooter
    4x5 Format
    Posts
    6,980
    Blog Entries
    29
    Images
    19
    Slight increase of aperture, slight decrease in duration. 1/125. E=i(t)
    Thank you.
    CWalrath
    APUG BLIND PRINT EXCHANGE
    DE Darkroom

    "Wubba, wubba, wubba. Bing, bang, bong. Yuck, yuck, yuck and a fiddle-dee-dee." - The Yeti

  7. #7
    Usagi's Avatar
    Join Date
    Apr 2007
    Location
    Turku, Finland. Northern Europe.
    Shooter
    Multi Format
    Posts
    360
    Images
    18
    Quote Originally Posted by davidave View Post
    I find it useful to be able to work in a luminance value as it is easier to figure out contrasts then go think about exposure after that. And you would still need a meter for a luminance reading.

    Do you mean EV values as luminance value?
    EV is easy - but c/ft^2, sounds complicated. Does any modern exposure meter even give option for unit like c/ft^2?

    I wonder what is it's standard (metric) equivalent. The thing that always bugged me when reading Adams' books - the use of units that are not used in science.

  8. #8
    Diapositivo's Avatar
    Join Date
    Nov 2009
    Location
    Rome, Italy
    Shooter
    35mm
    Posts
    1,844
    I presume at the time of Adams there were light meters around which gave you only the candles per square foot values, and you had to convert them in photographic values. It's the same measurement, if I get it right, expressed with a different unit of measure.

    My Minolta spot meter F comes with a conversion table between EV at ISO 100, candles per square meter, and foot-lamberts. E.g. EV 14 is equivalent to 2300 cd/m^2 or 670 fL.

    If you have to use a light meter, and you use it for photography purposes, then it's better to use one which gives you straight EV values, or maybe exposure "couples". I see no advantage in having a measure in another unit and then converting it to your purposes.
    Fabrizio Ruggeri fine art photography site: http://fabrizio-ruggeri.artistwebsites.com
    Stock images at Imagebroker: http://www.imagebroker.com/#/search/ib_fbr

  9. #9

    Join Date
    May 2010
    Shooter
    35mm
    Posts
    26
    @Chris,

    I'm not getting anything close to that. Try metering something that is 100FC at f/11 at 100ASA, not anywhere near 1/125.

  10. #10
    Christopher Walrath's Avatar
    Join Date
    Dec 2005
    Location
    Milton, DE, USA
    Shooter
    4x5 Format
    Posts
    6,980
    Blog Entries
    29
    Images
    19
    Addendum. That will be a slight increase in exposure, of course. But that can be accounted for in printing.
    Thank you.
    CWalrath
    APUG BLIND PRINT EXCHANGE
    DE Darkroom

    "Wubba, wubba, wubba. Bing, bang, bong. Yuck, yuck, yuck and a fiddle-dee-dee." - The Yeti

Page 1 of 4 1234 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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