Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,549   Posts: 1,544,634   Online: 672
      
Page 1 of 3 123 LastLast
Results 1 to 10 of 24
  1. #1
    Anupam Basu's Avatar
    Join Date
    Nov 2005
    Location
    Madison, WI
    Shooter
    Multi Format
    Posts
    504
    Images
    20

    Yay! for Sean ... and a quick question about manual flash

    Many thanks for starting this forum, Sean. I hope it will become a great source of help and information on macro photography.

    To tag a quick question to what is essentially a lame attempt to be the first person to post on the forum : is there any way to easily measure the amount of light lost to a diffuser or softbox attached to a flash and come up with a revised GN for doing manual flash photography? I can only think of testing as the alternative but am wondering if there is any other way.

    -Anupam

  2. #2

    Join Date
    May 2006
    Location
    Northern Aquitaine
    Shooter
    35mm RF
    Posts
    4,913
    ...apart from a flash meter, obviously.

    They aren't that expensive any more, even new.

    Cheers,

    R.

  3. #3

    Join Date
    Mar 2005
    Shooter
    Multi Format
    Posts
    3,404
    Not to be a complete idiot, but why do you want to use a softbox/diffuser when shooting closeup. If the flash isn't too far from the subject it is effectively a large, not a point, source of light and will give fairly soft lighting. If I weren't non-digital I'd show you some scans, but since I'm not you'll have to take my word for it.

    If your problem is specular reflections, a light tent -- a diffuser around the subject, not around the flash -- is the classical solution.

  4. #4
    df cardwell's Avatar
    Join Date
    Jul 2005
    Location
    Dearborn,Michigan & Cape Breton Island
    Shooter
    Multi Format
    Posts
    3,342
    Images
    8
    Well, there are two controls for light:

    Size, relative to the subject, and
    Distance from the subject.

    Distance from the subject affects the gradation across the field,
    so if you want an even light across the field, you move the light back,
    but if you want a variation across the field, the light belongs close to the subject.

    I suppose if one is making a clinical image,
    the light should be further away,
    but for an expressive image, you can bring it close.
    "One of the painful things about our time is that those who feel certainty are stupid,
    and those with any imagination and understanding are filled with doubt and indecision"

    -Bertrand Russell

  5. #5
    Anupam Basu's Avatar
    Join Date
    Nov 2005
    Location
    Madison, WI
    Shooter
    Multi Format
    Posts
    504
    Images
    20
    Quote Originally Posted by Dan Fromm
    If your problem is specular reflections, a light tent -- a diffuser around the subject, not around the flash -- is the classical solution.
    Dan, you are right. My problem is indeed specular reflections. But I can't figure out a way to put a light tent around insects in the field, as in this shot, for example.

    The other thing I have been trying is cross polarized flash, but so far my results have been miserable - need to experiment a bit more with it to figure out what the problem might be.

    -Anupam

  6. #6
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,288
    Images
    20
    Flashmeter or testing are the options. It's not that big a deal to test, if you don't have a flashmeter. Before I had a flashmeter, I tested all my studio reflectors and diffusers and came up with guide numbers, and would map out studio setups in advance before shooting, so I would have the right f:stop. As long as I didn't change the light-to-subject distance, I had some flexibility in moving the lights during the session. It was absolutely reliable.

    So do a test with slide film at a non-macro distance so you don't have to calculate exposure factor. Figure a softbox is going to cost you between 1.5 and 2.5 stops and shoot a series of frames a half stop apart.

    Then when you are shooting macro, don't forget to include the exposure factor for high magnification.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  7. #7

    Join Date
    Dec 2004
    Location
    Milwaukee, Wi
    Shooter
    35mm
    Posts
    3,242
    In a darkened room with a fairly bright light ie 200 watt hold an incident meter in a fixed position reading the central part of the beam. Take a reading at a particular shutter speed without the diffuser in place, note the fstop. Take the same reading with the diffuser in place at the same shutter speed. How much did the fstop change? The change is your correction.
    Claire (Ms Anne Thrope is in the darkroom)

  8. #8

    Join Date
    Jan 2005
    Location
    Minneapolis, MN US
    Shooter
    Multi Format
    Posts
    2,279
    Images
    4
    Quote Originally Posted by David A. Goldfarb
    (snip) So do a test with slide film at a non-macro distance so you don't have to calculate exposure factor. Figure a softbox is going to cost you between 1.5 and 2.5 stops and shoot a series of frames a half stop apart.
    I understand the advantages of using slide film (narrow latitude, no printing compensation), but would using b/w film and viewing the negs themselves be reasonably valid?

  9. #9
    David A. Goldfarb's Avatar
    Join Date
    Sep 2002
    Location
    Honolulu, Hawai'i
    Shooter
    Large Format
    Posts
    17,288
    Images
    20
    If you are good at reading negs, you could do that, but slide film usually will give you a more precise test. If you're using B&W neg film, you could print a contact sheet at minimum time for maximum black for this sort of test.
    flickr--http://www.flickr.com/photos/davidagoldfarb/
    Photography (not as up to date as the flickr site)--http://www.davidagoldfarb.com/photo
    Academic (Slavic and Comparative Literature)--http://www.davidagoldfarb.com

  10. #10
    naturephoto1's Avatar
    Join Date
    Mar 2006
    Location
    Breinigsville, PA
    Shooter
    Multi Format
    Posts
    1,819
    Images
    84
    Though small manual flash units are inexpensive, if you are working in the studio you may also want to consider using fiber optic lighting for close-up/macro work particularly as the subject gets smaller and smaller. Metering will be simpler and easier and you can see the actual effect on your subject. Another item that can be useful is to use small mirrors and work with 1 flash or light source.

    Rich
    Richard A. Nelridge
    http://www.nelridge.com

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