FLASH SYNC SPEED!
Electronic Flash units send out short bursts of high-intensity light. The speed of this light is very fast, a fraction of a second. This is relavent to photography because exposure is determined by aperture (size of the lens opening, in lensbaby terms the Aperture Ring) and by shutter speed (how long the "hole" stays open). When using flash, shutter speed does not affect the amount of flash that enters the camera except for the camera's ability to open and close the shutter. Most cameras come with a minimum shutter speed that synchs with an Electronic Flash. One must use this "flash synch" shutter speed or one that is SLOWER. The range of shutter synch speeds on cameras usually vary between 1/500 - 1/125 of a second. The newer cameras having the faster shutter speed synchs. You will have to determine which speed is correct for your camera. This leaves the apeture for controlling the amount of light entering the lens. The smaller the aperture, the less light that is allowed into the camera.
AMBIENT LIGHT AND FLASH
As stated earlier, shutter speed does not affect the amount of Flash light that enters the camera but it does affect ambient light. Ambient light is the continuous light (as opposed to the burst of light from a flash) that exists in the space you are in. Ambient light is also referred to as room light, available light or natural light. Lamps and sunlight are our most common sources of ambient light.
Photographers who use flash must "balance" the ambient light with their flash. A simple rule of thumb is that your aperture controls the Flash light and the shutter speed controls the ambient light. Usually the most pleasing Flash photographs have the Flash as the main light source with some ambient light filling in the background.
Try these two common examples for using flash with ambient light: 1. Outdoors on a bright sunny day, use flash to "fill in" the dark shadows created by the sun, a typical exposure would be 1/125 @f/16 with flash at full power or -1stop. 2. Inside at night, use Flash at full power and allow the shutter to stay open for 1/30 or 1/15 of a second or longer if you put your camera on a tri-pod.
SHOOTING ON A D70 WITH YOUR ORIGINAL LENSBABY
1. Go into your custom settings (CSM) menu on the D70 and set your pop-up flash to manual rather than TTL (if this is not apparent then your custom menu may need to be changed from simple to detailed in the set up menu).
2. Start by setting your flash power to 1/2 with a shutter speed/ISO combination that gives you an ambient exposure that is 1 to 1 1/2 stops too dark so your background does not go totally black. Test the ambient (non-flash) exposure by shooting a few test shots with the flash off. Play with the power of the pop-up flash from full power down to 1/16 to get proper exposure on your main subject(s).
This is a hard way to shoot as having a good amount of ambient light or some fairly contrasty light to deal with is always a good thing when focusing a Lensbaby. Not that Lensbaby flash photography is out, I do it all the time, it is just the more difficult way to learn to work with your Lensbaby compared with shooting in broad daylight.
Note that you will not want to use the SB600 Flash unit. The SB800 is a killer flash (Craig says) and a bargain at $329 (local camera store sells it for this so I assume it is available elsewhere for at least this good of a price). I own two and may add a third.
You will need to shoot a shoe mounted flash in manual mode or A mode as opposed to a TTL mode (the SB600 does not give you an A mode option). A mode gives you the option of letting the flash determine the amount of light to put out to match your f-stop.
Regarding aperture, I use f/4 almost exclusively and change my ISO and shutter speeds to get the ambient light I need and play with my manual strobes or put my SB800 on A mode to get the flash light that I need. I suggest changing your aperture to change the size and sharpness of your sweet-spot or slice of focus.
STUDIO FLASH PHOTOGRAPHY
Professional photographers use more complex Flash equipment which can be combined with soft boxes and umbrellas. Photoflex sells this type of lighting and mainly assessories and offers some nice tutorials on how to use it, photoflexlightingschool.com. Other popular brands are Speedatron, Broncolor, White Lightning, Dynalite, and Photogenic.