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Question on Neil's Off-Camera Flash book

haanshaans Member
edited November 2012 in flash & lighting
I read page 30 Neil's Off-Camera flash techniques. It says "For the example with normal flash, we had 1/250 second at f/11. For ambient light only, this would translate to 1/2000 second at f/4 (as an example). Yet, when going to high-speed flash sync we have an equivalent of 1/2000 second at f/2. Basically, we loose about two stops.".

Why are we loosing a two stops here when we go HSS?
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Comments

  • Neil vNNeil vN Administrator
    Hi there Haans ...

    As mentioned in page 24, it is because the HSS flash is dissipated over a longer duration now .... and a lot (most?) of the light now hits the back of the shutter curtains.

    With normal flash sync, the two shutter curtains are clear, and all the light from the flash pulse hits the sensor / film.
  • Thanks for clarifying Neil. I know much more about using normal flash and HSS after reading your book.
  • i think whats meant by "1/2000 at F /2" is that the flash power will only be bright enough to correctly expose the subject at f2 due to the flash having to fire more than once during the exposure to illuminate the whole frame
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