Toronto Photography Meetup Group

So I'm trying to learn how to use 2 wireless sb 800 flashes (borrowed from work) with some pocketwizards ... I'm not sure exactly how to set them properly with my camera (Nikon d70) ... do you divide the guide number of the flash by the distance away from the subject and use that as your aperature?? or how does that ... Say I want to underexpose ambient by 2 stops.. I meter the scene at say 1/500 at f8 ...

So I would set the camera at f11? then place 1 sb800 10 feet away?and a rim light behind the subject at say 7 feet away .. How do I get a properly exposed scene with ambient underexposed by 1 or two stops. anyonecare to help out??

F11 is only one stop greater then ambient. Using a chart someone put together on flicker for the SB800, located here http://www.flickr.com/photos/targophoto/2193600175/ , to have the ambient 2 stops less you'd put the main at 8 feet for f16. Based on the chart, f11 is at 12 feet.

I don't use Nikon gear...does your flash sync at 1/500?

Yes Nikon D70 has a flash sync of 1/500

Yes D70 will sync at 1/500... but PocketWizard might not. Crash10, the charts is great! but noted that it's at ISO100 only. D70 base ISO is 200, so you need to shift the chart by one stop.

Now to shift it by one stop instead of f8 it would be f11? etc etc
?

As per the equation...I found it easier working with multiple strobes to work in the opposite direction, divide the GN by the aperture to arrive at the proper distance.

The problem is the GN varies based on ISO, focal length, power, modifiers, etc so I think a light meter is a great investment. Last night, I was getting exactly what I wanted inside 20 seconds.

I use to have a piece of string that had fstops measured out at 1/8th power.

Any light meters you would suggest?? Just any sekonic should do??

Yep. ISO is one stop so if you copy the chart just shift everything over one.

Notice power is also one stop. Ie, 1/2 power is one stop difference from full power.

I don't know the differences between them all nor the various bells and whistles. I have a Minolta IV and I've had it for a long time. Maybe you can rent a meter to get a feel for mileage?

Even if you get a light meter I'd still invest the time understanding the math etc. The string helped as it gave me a visual reference to the point that sometimes I don't need a meter at all.

Someone should make a BB/Iphone calculator app with all the variables!

Good catch!

If anybody gives the string thing a try don't do it for full power..since power is a stop you want to be able to move both up and down.