Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,563   Posts: 1,545,302   Online: 773
      
Page 1 of 3 123 LastLast
Results 1 to 10 of 26
  1. #1

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98

    sunlight vs.electronic flash for BW film speed tests

    Will electronic flash with correct filtration affect B/W film speed testing vs. using only natural sun light?

    I found following (average values):

    daylight around noon with clear sky and electronic flash have around 5,500 K

    morning / afternoon sunlight ~ 4300K-4500K - flash with #3409 Roscosun 1/4 CTO (converts 5500K to 4500K) should be within that range

    It looks like color temperatures should match pretty close. Are there other factors except just light color temperature which will make a difference?

  2. #2
    AgX
    AgX is offline

    Join Date
    Apr 2007
    Location
    Germany
    Shooter
    Multi Format
    Posts
    8,615
    Yes, the reciprocity of the emulsion is of influence if the exposure with flashlight would be significantly shorter than with sunlight.

  3. #3

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    Do you mean exposure as a flash duration ? If yes it looks like Nikon SB-28 (which I can use) has ~1/1000 s at 1/2 power. Will that be OK?

  4. #4

    Join Date
    Jul 2010
    Location
    Southern USA
    Shooter
    Multi Format
    Posts
    3,842
    The color temperature of daylight can vary considerably depending on the position of the sun and atmospheric conditions. It can go from below 5000K to over 12000K. For this reason artists favored studios with northern facing windows. In addition it varies with altitude with the temperature incrreasing for each 1000 ft. It is not a very reliable reference source.
    Last edited by Gerald C Koch; 03-08-2013 at 03:55 PM. Click to view previous post history.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #5

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    Quote Originally Posted by Gerald C Koch View Post
    The color temperature of daylight can vary considerably depending on the position of the sun and atmospheric conditions. It can go from below 5000K to over 12000K. It is not a very reliable reference source.
    yes you are right, that's why I was thinking that maybe using electronic flash with correct filtration close to morning or afternoon daylight temperature can be used for film speed / development test. I used reference to the sunlight bc I'm going to use film under sunlight, only test would be performed using flash.

    I'm trying to do the film test as described in Way Beyond Monochrome book using stouffer step wedge. I was trying to use sunlight but always light changes (or I'm too slow) all the time at my location and I was not able to get the consistent results. That's why I was thinking to use flash with gel on it to be close to the sunlight.

  6. #6

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    I checked technical information for a few films and it looks like below 1/1000s should not be a problem. Just to be sure I can use flash at full power what should lower SB-28 flash duration, based on tests I found, to ~1/300s. Please see attached (I did not know that for TRI-X Kodak recommends +10% development at 1/1000s).

    If I will take care about high intensity reciprocity failure and gel flash to lets say 4500K (bc I rarely take photos at noon). Will that be OK to test film speed / development time in that environment if I'm going to take "real photos" outside in the sunlight using results of the test performed inside with flash like described above?





    .
    Attached Thumbnails Attached Thumbnails Reciprocity-Failure.jpg  

  7. #7
    Ken Nadvornick's Avatar
    Join Date
    Mar 2005
    Location
    Monroe, WA, USA
    Shooter
    Multi Format
    Posts
    3,296
    Images
    48
    Interesting idea. Are you reasonably certain that the flash unit you intend to use has an acceptably repeatable output duration?

    Ken
    "They are the proof that something was there and no longer is. Like a stain. And the stillness of them is boggling. You can turn away but when you come back they’ll still be there looking at you."

    — Diane Arbus, March 15, 1971, in response to a request for a brief statement about photographs

  8. #8

    Join Date
    Jan 2012
    Location
    New York, NY
    Shooter
    Multi Format
    Posts
    98
    Good point, I tested it using flash meter. Flash was on the tripod facing wall, I measured with meter against the wall facing flash. I fired 30 times at 1/2 power - same readout on flash meter. I will test using full power what will allow to decrease flash duration below 1/1000s.

  9. #9
    ic-racer's Avatar
    Join Date
    Feb 2007
    Location
    Midwest USA
    Shooter
    Multi Format
    Posts
    6,221
    The typical 'in camera' exposure index test checks that the system of lens, aperture, film, shutter and meter will produce an adequate exposure of the film. Using a flash for the test negates some of the benefit of the test.

  10. #10

    Join Date
    Aug 2006
    Shooter
    Medium Format
    Posts
    544
    Why would you bother 'testing' films? That's the manufacturer's job. Read their data sheets—why would they lie about this stuff? Test your light meters and cameras' shutter speeds. Don't waste you film with urban legend nonsense, go out and make photographs—that's what film is for!
    testing...

Page 1 of 3 123 LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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