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Under exposing at max sync speed

LoriclappLoriclapp Member
edited October 2013 in flash & lighting
I understand that shutter speed effects ambient exposure and F stop effects flash exposure. And I know that when shooting a darker subject with a bright background, I should start at max sync speed. My question then, is how do I underexpose if I am already at my max shutter speed. I did some test shots yesterday with this set up, and I (incorrectly, I think), used the fstop to decrease exposure on the background. But it seemed to work - maybe because I did this before I added flash. But once I added flash, I couldn't use fstop to decrease exposure on the background, because this would effect my flash exposure, correct?

I read the information at this link:

and it seems to say that you are underexposing the ambient light, with your Fstop.

If your Fstop effects flash exposure, how/why are you using it to decrease ambient light on background, without effecting flash exposure??


  • Loriclapp:

    Manually set your exposure for the ambient light, this is when you over or under expose the ambient light. After you have the ambient exposure set you set the flash exposure. When using TTL adjust the flash using Flash Exposure Compensation (FEC), when the flash in manual you’ll adjust the power setting or distance to subject.

  • Loriclapp you said: "I understand that shutter speed effects ambient exposure and F stop effects flash exposure."

    Assuming you are using TTL flash, this is not really a correct statement because TTL flash will try to expose the subject correctly regardless of what you do with shutter, aperture, and ISO. So if you are using TTL flash, set your ambient exposure to what you want using shutter, aperture, and ISO and let TTL flash expose the subject. If the subject is too bright / dark, use FEC accordingly.
  • Sorry - I left out that I am using manual flash. And I understand how to meter and set my camera for ambient. My question is, if I am starting at max sync speed, which is 200, and I want my background to go darker....I can't increase my shutter speed or I will go into HSS. And if I close down my aperture, wouldn't that effect my flash exposure, and not my ambient exposure?
  • Yes close down the aperture to darken the background. You will have to increase the power setting on your flash or decrease the flash distance to the subject to keep the flash exposure the same.
  • "I understand that shutter speed effects ambient exposure and F stop effects flash exposure." this is one very common misconception among photographers. i find it frustrating that their are many "pros" teaching about flash in this way. luckily good people like Neil dispel the myth :)

    what ur missing is that shutter speed Fstops and ISO all affect ambient exposure. however only fstop and ISO affect flash exposure. when going to max sync speed is not enough to underexpose the ambient u must use fstop and iso to bring down the ambient exposure as well
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