Sony HVL-58AM Flash - GN confusion.

Discussion in 'Photography Equipment & Products' started by ZWolfe21, Mar 23, 2010.

  1. ZWolfe21

    ZWolfe21 TPF Noob!

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    Ok well, here comes another question from an inexperienced photo freak that has reached his witt's end. Sony HVL-58AM. Wonderous flash, the bit i'm able to understand the dang thing. Has a Guide Number of 58 (at 105mm zoom on the flash)...

    Now... is that in Meters... or Feet... Now for guide Number Calculations, that being.

    GN / Distance = F-Stop

    Distance is relivent, 58 ft vs 58 meters is a huge difference. Example...

    Feet: 58 / 10ft = 5.8 f-stop at iso 100
    Meters: 58 / 3m (3.048m = 10ft) = 19 ft stop at iso 100.

    Or whatever closest f-stops those are.

    This of course having the flash set at 105mm zoom full power, according to their documentation. Now this model has a zoom function that apparently moves the bulb inside the unit to widen the flash area, while reducing its GN 105mm to 24mm in 6 steps. Theres a whole set of charts for the GN for different flash zoom settings, shutter speeds and flash power settings. You wouldn't photograph something at 3 meters with a zoom setting of 105mm, at least thats how I see it right now. And of coarse iso 200 you'd close your stop by 1, and open up a stop if you reduce the power by half, so on and so forth.

    I think its meters... According to two websites that are not sony. But on their website they say it has an effective range of MORE THAN 45 feet with a guide number of 58.

    So i'm confused, new to a real camera flash. At $500.00 I intend to conquer this freaking thing and would really like someone to lift this fog of confusion. So feet or meters? Can anyone help me here? Any good material on flash basics would be valued beyond belief to me right now lol.

    Side Note: I'm hoping to eventually learn enough to become a valued member of these forums rather then a knowledge digging burden :grumpy:
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    You should be able to find out if it's feet or meters somewhere...the manual maybe, or the spec sheet online.

    My guess is meters. The Canon 580EX has a GN of 58m,
     
  3. ZWolfe21

    ZWolfe21 TPF Noob!

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    Ah Ha... Wise Mike... Specifications online did say 58 meters. Manual doesn't though... thats odd. I've read it 10 times, i'm sure its not in there lol.

    I have learned one thing... its much harder to figure out when this flash thinks for itself.
     
    Last edited: Mar 23, 2010

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