Results 1 to 5 of 5

Thread: Flash Exposure Question

  1. #1

    Join Date
    Nov 2001
    Posts
    22

    Flash Exposure Question

    i just starting using flash with my large format equipement. here is my question . i know that the sync speed is not important with large format lens since they are leaf shutters. but here is the question. if i use a flash meter and get a f stop of say f22, if i place the shutter speed at 125th of a second, the amount o f ambient light entering the camera is different than if i set the the shutter s peed at 1/2 second for example. my question is, how do i determine the shutter s peed to set the flash so that the ambient light exposure and flash exposure is c orrect? thanks

  2. #2

    Join Date
    May 2006
    Location
    Arizona
    Posts
    377

    Flash Exposure Question

    For a "balanced" look you need the ambient light and the flash to each provide 1/2 the light. If you have a flash that will give F22 (ignore the shutter speed) you need to adjust your shutter speed to whatever will also give f22 for the ambient (1/2, 1/8,...whatever). If you're using negative film you can stop there - you'll get slight overexposure which is a good thing under the circunstances. If you're using transparency film you would close down an additional aperture stop to avoid burning out the highlights. For a better rendering with all films a reduced popwer "fill flash" is a better option. With this you determine the exposures as before but slow the shutter speed by one stop to allow the ambient to overpower the flash by one stop, then close the aperture by one stop to balance the exposure to the ambient and effectively cut the flash power by 1/2. You can carry this even further for a compensation of 1 1/2-2 stops depending on the subject, the situation and your taste. And you can of course compensate in the other direction also to knock the background down or eliminate it.

  3. #3

    Join Date
    Mar 1998
    Posts
    1,972

    Flash Exposure Question

    I determine what the shutter speed should be based on what I want the final iamge to look like. In some situations I wantthe flash to be mostly "invisible" in the over all look of the image, in others I want it to be more pronounced all the way to the point of excluding any traces of ambient light.

    Now if you are menaing balancd one thing that will help is to use a meter that can read both ambient and flash simultaneously or let's you put into a memory function the flash reading and then seperately read the ambient light and see the numerical relationship between the two readings as you change shutter speeds.

  4. #4

    Join Date
    Jun 2000
    Location
    Redondo Beach
    Posts
    547

    Flash Exposure Question

    No one has mentioned it but depending on the circumstances you may encounter 'ghosting', that is a double or faint second image in addition the first image, which sometimes occurs with slower shutter speeds.
    Jonathan Brewer

    www.imageandartifact.bz

  5. #5

    Join Date
    Jun 2000
    Location
    Redondo Beach
    Posts
    547

    Flash Exposure Question

    I did not mention that 'ghosting' tends to come into play as open up your lens, and tends to be less of a problem as you close down.
    Jonathan Brewer

    www.imageandartifact.bz

Similar Threads

  1. simple Metz flash question
    By Henry Carter in forum Style & Technique
    Replies: 5
    Last Post: 1-Mar-2006, 06:13
  2. Manual Flash Question
    By brian steinberger in forum Style & Technique
    Replies: 2
    Last Post: 30-Oct-2005, 08:15
  3. "Post Exposure" book question
    By brian steinberger in forum Resources
    Replies: 7
    Last Post: 14-Oct-2005, 16:19
  4. Flash Exposure For Dual Flashes And Bellows
    By Pete Gregar in forum Style & Technique
    Replies: 3
    Last Post: 24-May-2001, 17:35
  5. Flash question
    By Natha Congdon in forum Gear
    Replies: 2
    Last Post: 23-May-2000, 06:28

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •