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Question about info in Neil's book

LoriclappLoriclapp Member
edited September 2013 in flash & lighting
I am reading Neil's book "Off-Camera Flash" and I have a question. On page 35 (in case anyone wants to know), in one place it says, "with TTL flash, the flash output will follow your choice of aperture and ISO". Further down that same page, it says "With TTL flash, our choice of aperture (within reason) has no effect on flash exposure".
Even though this sounds like a contradiction, I am 99% SURE it is not. I just don't understand how it's not though. I am trying to make sense of off camera flash, and my main problem is knowing what to adjust when I have too much or not enough flash.

Can someone explain the two statements above to me so it makes sense? TIA. And again, I am NOT trying to point out a "mistake" or anything like that. I know it's not a mistake - I'm just not "getting" it!!

Comments

  • It is not a contradiction...
    "with TTL flash, the flash output will follow your choice of aperture and ISO"

    In other words, the TTL flash output amount will be the same if you change the f stop and/or ISO. Try it out...

    ""With TTL flash, our choice of aperture (within reason) has no effect on flash exposure"

    Same thing. You change the f stop and TTL will adjust the power output to stay consistent. open up and less power output. You stop down and the flash will increase output.

    In ETTL, the flash and camera "talk" to each other. Camera says "hey flash, the crazy camera person just changed f stop from 2.8 to 5.6. You need to kick up the output now!" Same conversation takes place for ISO.

    If you need to hear them talk, hold the camera and flash really close to your ear. Just make sure no one is watching or it won't work :)

    rc
  • This is how I see it.

    First statement. If you change either aperture or ISO, TTL will compensate for a correct flash exposure.

    Second statement. If you change your aperture within reason it will have not effect on flash exposure. I believe Neil is talking about the exposure of the actual subject, not flash output which will either increase or decrease automatically when you adjust the aperture.
  • Okay, I think that makes sense to me...the first statement means that when I adjust my fstop or ISO, the flash will automatically adjust itself for the changes I made. The second statement just says that even though I change my stop, the flash exposure will not change, because it will adjust itself for my changes....right? Even if I'm not saying it right, I do think I get it now. See, I KNEW it was me!!! Thanks for the explanation!!
  • PS, I tried holding it really close to my ear to hear the flash talking to the camera - but all I got was a high pitched squeal. Guess I need to have my hearing checked!
  • Sounds like you go it. The problem is they are talking in Japanese so that probably why you are having trouble :)
  • And darn. trevor beat me again to the answer :)
  • Loriclapp,

    "Okay, I think that makes sense to me...the first statement means that when I adjust my fstop or ISO, the flash will automatically adjust itself for the changes I made. The second statement just says that even though I change my stop, the flash exposure will not change, because it will adjust itself for my changes....right? Even if I'm not saying it right, I do think I get it now. See, I KNEW it was me!!! Thanks for the explanation!!"

    sounds like you got it!

    Rudy

  • Neil vNNeil vN Administrator
    Loriclapp said: Okay, I think that makes sense to me...the first statement means that when I adjust my fstop or ISO, the flash will automatically adjust itself for the changes I made. The second statement just says that even though I change my stop, the flash exposure will not change, because it will adjust itself for my changes....right? Even if I'm not saying it right, I do think I get it now. See, I KNEW it was me!!! Thanks for the explanation!!
    Exactly!

    These are different ways of saying that your TTL flash exposure will remain the same, even if you change your settings ... because the camera and flash will adjust the flash power for you.

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