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DPChallenge Forums >> Hardware and Software >> Flash functioning question...
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 03/16/2007 03:26:47 PM · #1
Hi, I own a 580ex and I've been reading a lot about it but I have some questions: it is mentioned some times that the zoom of the flash was adjusted somehow, what is this for? how does this affects the light getting to the subject? and ultimately, when do I use this function of the flash?

I know where to adjust it but not really what is the purpose.

Thanks in advance,

Ivan
03/16/2007 03:39:46 PM · #2
It has a head that zooms in and out depending on what focal length you're at, to give you better coverage for that area. For longer focal lengths it "narrows" the beam of the flash, and vice versa. I think it covers from 24mm to 105 mm. The 580EX takes it a step further and compensates for "cropped" sensors too, so it knows that say a 50mm on your camera is more like 80mm and adjusts the zoom for that.
 03/16/2007 04:07:20 PM · #3
Thanks, so I could also use it to better focus the beam in the subject? or to increase the distance?

For example if I am using a 50mm lens, the camera sends this information to the flash and it zooms at 50mm, however if I feel I need more flash coverage should I zoom in more, less? am I understanding this at all? ;)

I am also asking in terms of using this creatively.

Thanks
 03/16/2007 05:45:03 PM · #4
It does it automatically for you, but you could manually play around with it if you wanted. Think of it kind of like a Mag flashlight where you can focus the beam. It narrows the beam for longer focal lengths to concentrate more light in the field of view, thus it doesn't have to put out as powerful of a flash. BUT, if you put a diffuser on there it negates that feature anyways.

I've never played with it before, but say your focal length is 24mm, but you set the flash to 105mm you'd probably have a rectangle in the center that is lit while everything else is dark. -just a guess.
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