Speedlight Flash lighting w/ Zoom lenses - SB-700 & Nikon 55-200mm

Started Dec 20, 2012 | Questions thread
ch382
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Re: Speedlight Flash lighting w/ Zoom lenses - SB-700 & Nikon 55-200mm
In reply to BobSC, Dec 21, 2012

BobSC wrote:

With flash photography, there are three variables:

  • aperture
  • distance
  • flash power (& ISO)

The focal length of the lens doesn't matter, and neither does the shutter speed.

The sb-700 has a zoom head that concentrates the flash power. If you had it on the long setting, then it has a guide number of 95 at iso 100. If you had the lens wide open (f/5.6, right?) and use direct flash, then it should work at 17 feet (5m). If you bounced it off the ceiling, then a lot less. If you put the iso to 200, then 24 feet. at 400 then 48 feet, and so on.

If you were bouncing, then you lose at least two stops of light. So then at iso 400 you get back to 17 feet, or less.

Thank you for the detailed technical response Bob. I think knowing the relationship between the guide and the ISO is def gonna help.

So if I have it in say, A mode and shooting wide open at f/5.6 (which you are correct about btw:)) - or anything else for that matter, dialling up the ISO- would make the picture lighter (that I understand).. But It doesn't actually make the flash STRONGER at all, does it? It just makes everything brighter? ye?

Thanks again!

 ch382's gear list:ch382's gear list
Nikon D7000 Nikon D800 Nikon AF-S DX Nikkor 55-200mm f/4-5.6G VR Nikon AF-S DX Nikkor 35mm f/1.8G
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