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Author Topic: flash panickers  (Read 1538 times)

Offline Bigbill

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flash panickers
« on: November 04, 2010, 08:30:59 PM »
Hewwo from Hurricane City !!

Now then,,,the beautiful art of Flash--- a very mystical thing,,so,,,,if like me you get a huge headache when trying to get it right,you may find the following link useful
http://nikonclspracticalguide.blogspot.com/
I,m crap at my sb800,,and ive found the link very helpful,,hope you do !! :)

Shine On



Offline nickt

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Re: flash panickers
« Reply #1 on: November 05, 2010, 10:23:49 PM »
I think the Neil Van Niekirk website has got to be the ultimate in understanding flash.  http://neilvn.com/tangents/
Nick

Offline Carlj

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Re: flash panickers
« Reply #2 on: November 07, 2010, 12:20:31 PM »
There are a few out there. I use Gary Friedman's, thanks to Sony emphasis, but the strobist blog and flickr group is very useful too!

Carl

Offline Bigbill

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Re: flash panickers
« Reply #3 on: November 08, 2010, 09:07:47 PM »
hewwo from sinking Sheffy,,,,

so,does the GN change or is it constant ??

shine on

Offline Graham

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Re: flash panickers
« Reply #4 on: November 09, 2010, 05:57:55 AM »
hewwo from sinking Sheffy,,,,

so,does the GN change or is it constant ??

shine on
 Hi Bill.
            The Guide Number is the total output on full power and is constant. It is usually quoted at a certain ISO, usually 100.
            If you were then to increase your ISO to 200 you will have effectivley doubled your flashes "output". IE gained another stop.
                        Graham. :)
« Last Edit: November 09, 2010, 06:00:09 AM by Graham »
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Offline Jonathan

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Re: flash panickers
« Reply #5 on: November 09, 2010, 07:34:47 AM »
But it also changes.....modern flash guns use zoom heads with fresnel lenses to give a variable GN - i.e. more at 200mm zoom than 28.
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Offline Bigbill

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Re: flash panickers
« Reply #6 on: November 09, 2010, 09:49:23 AM »
Hewwo from submerged Sheffy

Now then,thanks everyone,,,JR,,this is where my ideas went out the window,,,,the GN does change,,wrecked all my ideas that did,,,
I see that you can actualy work out the NG with distance,ISO,aperture,,,,how the bloody hell are you supposed to know the F No first ??(why does the sb800 have a gn of 125 ??)
As for swivelling the zoom head,,,,,lets not go there !!
Ive ordered Neil van Niekerks book about the subject,,,,should REALLY confuse me !!

Shine On

Offline Graham

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Re: flash panickers
« Reply #7 on: November 10, 2010, 05:16:15 AM »
But it also changes.....modern flash guns use zoom heads with fresnel lenses to give a variable GN - i.e. more at 200mm zoom than 28.

       Zoom heads, fresnels etc. are just light modyfiers designed to concentrate the output into a smaller area in the same way that difusers, brollies etc are designed to soften the output.
       You could put a fresnel on your studio lights and concentrate the beam of emitted light but you wont have increased the output.
       As you can see I understand the Guide Number to be a guide to the flashes output.
                            Graham.
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Offline Jonathan

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Re: flash panickers
« Reply #8 on: November 10, 2010, 07:59:19 AM »
Yeah the Guide Number is usually quoted at maximum zoom.  However, if you widen the zoom the lens spreads the light out more.  Check out the lookup table on page D-22 of the SB900 manual.  At full power, 100 ISO in metres the guide number of the SB900 is between 13 and 56 depending on the zoom.

http://visualarts.mit.edu/downloads/manuals/Nikon_SB900.pdf (biggish download)

>> (why does the sb800 have a gn of 125 ??)

That's guide number measured in feet.  Guide number = shooting distance X f-stop / ISO factor

If you measure shooting distance in metres you get a metric guide number, if you measure it in feet you get a bigger one.
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Offline Bigbill

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Re: flash panickers
« Reply #9 on: November 18, 2010, 04:07:47 PM »
Hewwo from damp Sheffy,,

Now then,,,ive bought the book by Neil Van Niekirk (on camera flash) and i can highly recommend it,,,,
it is easy to understand and very very informative !
ive always been crap with my speedlight,,at last its starting to make sense,
DONT buy it via his website though,get it from Amazon UK and save yourself a few quid.
Thanks to all for the input  :D

Shine On

 

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