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Position:Home>Visual Arts> SB 600 Flash Unit Help?Question: SB 600 Flash Unit Help!? Measured Guide Number (GN) in feet, ISO 100:
Zoom Setting GN 14 mm 36 (40 - 1/3) 24mm 64 (56 + 1/3) 35mm 71 (80 - 1/3) 85mm 100 (110 - 1/3) What's a guide number!? Where does zoom settings fit into this!? Actual zoom buttons!. Anything else I should know about!? As you can see, I'm an idiot when it comes to this!. Looking to use it on a Nikon D50 with a 35-70mm f2!.8 Nikkor, 12-24mm f4 Tokina or 17-50mm f2!.8 Tamron!.Www@QuestionHome@Com Best Answer - Chosen by Asker: Guide numbers are just a measurement of flash light output, usually always measured at 100 ISO!. It is a way to compare flash power amoung various flash units!. You can use the guide number to calculate f stop, but you must know the distance to your subject!. For instance, if your subject in 10 feet away, and your guide number is 100, you would divide 100 by 10 and your f stop should be f10!. Another example, if your subject was 8 ft away and your guide number was 71, you divide 71 by 8, and your f stop will be f 8, (close as you can get to the 8!.8 answer)!. As ISO speed goes up, so will the guide number!. If you have a guide number of 100 at ISO 100, the guide number will double to 200 at ISO 400!. The guide number becomes lower at wider focal ranges because the flash cannot cover the greater area!. So at 85mm, the flash only has to illuminate a relatively narrow path of area!. At 14mm however, the flash must try to illuminate a much greater area, and so the guide number will be lower, (meaning the distance between the subject and the flash cannot be as great as it can with a more telephoto focal length, such as 85mm)!. Now you see why modern cameras and dedicated flashes use the TTL, (through the lens) metering method!. The flash automatically outputs the correct amount of light based on the feedback from the digital sensor / film plane!. I think Nikon also uses distance as part of the TTL calculations!. In cases where you are using a non dedicated flash on a camera without TTL, you are much better off to use a incident flash meter rather than trying to figure flash settings by guide numbers!. The D50 and SB600 combo is a dedicated camera / flash arrangement and will take care of flash output automatically!. You should have no problems!. Just be sure the flash is set to the TTL mode and not manual mode!. Hope some of that made sense! :-) steveWww@QuestionHome@Com GN is the output of the flash!. (power - max) SB600 GN100(32 in meters - 3 feet to a meter roughly) - this is at 100iso - fotogs talk 100iso or specify different So example: subject is 4m (12ft) from the flash, what fstop will give good exposure!? (50mm lens on FF) GN/Fstop=distance or distance = GN/Fstop so gn32/f8=4meters or gn100/f8=12feet - roughly - this might to be easier if you work in meters (a meter is roughly 3 feet or a bit longer than a yard), and photography is meteric (eg mm, fstop/gn et cetera) If you zoom the flash out it will give a direct beam - like telephoto view - this is it at its most powerfull concetration!. On the wider settings the beam is less powerful - as per the GN dropping!. Are you with me!? aWww@QuestionHome@Com Only to add to Steve and Antoni here is a cheat sheet for your flash and a few others!. http://www!.night-ray!.com/PhotoCheatSheet!.!.!.Www@QuestionHome@Com |