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Bounce Flash Photography

lawreolawreo Member
edited November 2014 in flash & lighting

Do you have to increase your flash power to compensate?

Is TTL still accurate when you bounce your flash? Does TTL compensate for bounce flash?


Thankss

Lawreo




Comments

  • Do you have to increase your flash power to compensate?

    Typically yes but of course it does depend on the conditions. The light has to travel further to get to subject. The Canon flash system has provides distance information but only of the flash head is pointed forward. As son as you tilt or swivel that is disabled however it is only a verification. Canon still uses the pre-flash and reflected light back to determine exposure.             

    Is TTL still accurate when you bounce your flash? Does TTL compensate for bounce flash?


    You are calling it TTL so I assume you are using a Nikon. Canon calls it ETTL. I know Neil switched to Nikon many years ago for the AF (for sure) and flash accuracy I think. Nikon is supposed to have a better flash system but I don't what that actually means or how that system works.

    As for Canon I will say TTL is supposed to compensate but it is a computer trying to make it's best guess of what you want. I have always regarded TTL as ball park. Depending on what the subject is wearing and how that light reflects back to the camera will effect the exposure. I imagine Nikon is pretty close, it just may have better algorithms.     

    I have been in conversations about a diffuser on the flash. The system does not know a diffuser is on the flash but is supposed to compensate. It is still ball park for me.

    TTL gets me close but if I want those white exposures to be precise I still check the histogram and adjust the flash exposure compensation (FEC).

    I can't speak for Nikon. I do know with Canon you can adjust FEC and aperture independently and they work together on the Nikon system. Not sure how it effects it.

    I don't worry about TTL compensating. I just try to predict the FEC before I shoot and then just adjust as necessary.                     
  • Hi lawreo:

    Regarding your first question, theoretically yes but in practice probably not. If you are in M mode there's no increase per se, you just establish the proper level of flash output for your scenario and circumstances (bouncing). If you are in TTL (on to your second question) then yes the flash should do it (increase power) for you, even when you're bouncing, since it has determined the circumstances, including distance, and you shouldn't have to use exposure compensation. That said, as Neil writes in his latest Tangents post, sometimes the flash on TTL still underexposes images due to its conservative light output and that is one reason he will go to M mode, to get maximum light output. 

    So, to answer your questions. #1: Not really, unless you look at the camera screen and decide you need more or less flash, like adding more salt to a recipe than called for. #2A: Yes. #2B: Yes.

    Here is what Neil wrote exactly, in response to a question:

     22Neil vN November 16, 2014 at 12:56 am

    In theory, TTL should follow and give proper exposure … but I’ve found that with (Nikon) TTL, the camera is hesitant to dump full power and will tend to under-expose when what I really need is a lot of juice.

    Also, with this specific sequence, I’m kneeling on the floor close to the B&G’s table. My position is static as is the direction I bounce in … so I might as well keep to manual flash for consistency. But really, this was done to make sure I get max juice from my flash.


  • Thank you Zenon and Skipperlange for your valuable comments and suggestions . Much appreciated.

    Regards,

    Lawreo

  • Neil vNNeil vN Administrator
    Re Bounce flash: 

    >> Do you have to increase your flash power to compensate?

    In theory, no.  The pre-flash should take care of the TTL metering. In practice, you might very well have to adjust your FEC. 

    Become accustomed to your camera and flash's behavior to anticipate how it responds and how much FEC might be needed usually.


    >> Is TTL still accurate when you bounce your flash? Does TTL compensate for bounce flash?

    In theory, yes, it is still accurate, because of the pre-flash that is metered.  In practice .. same answer as above. 




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