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BFT Power Reduction?

Has anyone found the BFT stealing a little bit of power as the flash is fired? Can the BFT be sticking out too much so this happens? I think this may be happening to me sometimes but really can't be positive.I have it sticking out 3-4 inches from the flash tube. I do primarily events, and my main use for it is to protect the eyes of people behind me.

Just curious, and maybe I have to shorten up a bit?

Dave

Comments

  • TrevTrev Moderator
    Dave,

    The BFT is always going to 'steal' flash power mate, it's black, it absorbs light, it stops light spill which under normal circumstances would fall onto the subject; but, it's also bloody brilliant. (Which obviously you know :) )

    Just up the power or wider aperture or make sure you are bouncing off objects to the best you can.


  • Thanks, Trev. I'll try not to blind the people behind me as I shorten it up a bit :)
  • TrevTrev Moderator
    edited August 2018
    Dave,

    When I use mine, I only have it out by around 2-3 inches (50-75mm) at most. Never used it longer than that at all, and no problems so far doing it that way for me.

    Oh, don't forget, on your flash head, make sure you manually zoom it right in whatever the maximum it, don't let the flash head 'talk' to the camera when you change zoom setting on your lens, always be in control, that also helps.

    If you are using say a 24-70mm lens, then that lens will dictate the flash head's zoom settings with a much wider angle and that loses a LOT of power by spreading it out, zoomed right in, it concentrates the flash beam much narrower to the bounce surface, thereby gaining some more power compensating for the BFT's black surface light absorbing effect.

    You should do that anyway just from the get to, don't dick around with any 'zoom' setting on head, straight to the max first up.

    Canon 180mm (dunno about latest flash heads for them); Nikons 200mm zoom.


  • Thanks, Trev. yes, my Flashpoint (Godox) flash can zoom to 200 mm, but I've been having it at 24 mm, thinking it was better to spread the light wider. I'm going to go with your suggestion for the next few events and have it at 200 mm. I never have it in "auto" zoom.

    Dave
  • TrevTrev Moderator
    Dave,

    Having your light zoomed out to 24mm, thinking it's a better spread is not the best, remember, once the light reaches the bounce object, reflects back, it's already spreading out anyway.

    If you were shooting direct flash, well yeah, that's what makes sense.

    eg: Zoomed in to 200mm, shooting up into ceiling say, it's probably already back to, guessing, around 150mm, more or less, then, and this is the part you need to understand, it's then coming back at a much wider spread again, so it's in effect spreading twice before it even hits the subject/s.

    The higher the ceiling or further away the wall/bounce object is, the wider again the spread will be both ways.

    The benefit is then slightly less flash power is needed, or, in the case of BFT, no need to up the power (maybe-depends) on flash head.

    Trev


  • Neil vNNeil vN Administrator
    If you zoom wide, the BFT will eat a lot more of your flash's power than if you zoomed tight. So zoom tight. 

    Even if you zoom your flash tight, you still have that massive "softbox" behind you to give you soft light. 
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