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Well, Jenifer, I'll try to help. FIrst, slave lights merely refer to the notion that those strobes will trigger without wires - they fire off when their sensors "see" the short duration flash from another strobe. SO what you've got is more lights, basically. Now as for the thing with setting one light "2 stops" less than another...the first notion to get is that "stops" are just photography-speak for twice or half as much. F4 lets though twice as much light as f5.6, and f 2.8 lets twice as much as f4, right? So the term comes from the lens side of things, but can be used for the other factors in shooting. For example, 1/125th second is 1 stop different than 1/60th - it lets in half as much light (this time due to the shutter being open for less time). Or ISO400 is two stops faster than ISO100 - because the wntire ISO numbering system was originally based on the "stops" concept. SO to make things easier, it was decided that film (or a CCD setting) that is twice as sensitive to light as another would have an ISO number twice that of the "slower" version. 100 doubles to 200, 200 doubles to 400 - voila! - two f-stops of difference. That sound okay? Now the reason you want to have different amounts of light coming from your different flash units is simply artistic - if all the flashes are putting out the same amount of light and they're all equidistant from the subject, the photo will tend to look flat and uninteresting. Light is what gives a photograph it's beauty, or lack thereof. So let's think of the subject sitting at the center of a clock, with your camera being at the 6 o'clock position, okay? If you have a main flash positioned at 4 o'clock and nothing else, then the subject's face will be well lit on her left side but her right side will be lost in shadow. So you want to fill in the right side of her face with some illumination, not so much to make it look like a DMV shot, but enough to allow one to see her eyelashes and so forth. So you use a fill flash at about the 8 o'clock position (and maybe at a different height than the main light as well - you can go pretty crazy if you want). SInce we don't want too much light to fill in the shadows, the fill flash should be set to 1 or 2 "stops" less light output than the main. If you add a hair light at the 12 o'clock spot but positioned on the floor and aimed up towards the subject's head, you don't want that to be too overpowering, so again you will cut back it's light output (or just use a weaker lamp). As for how to adjust your camera - when you are working with multiple strobes, it's pretty much necessary to get a flash meter. This is a light meter that can take a reading of the sub-1/1000th-second blink of light the strobes put out. Usually using the incident type meter is best, particularly in a studio setting, so basically you stand where the subject will be sitting, point the diffuser dome of the meter towards the camera lens, and trigger the flashes. The meter will tell you what settings you need. Now there are manual ways to calculate that, but trust me when I tell you you don't want to go there. I hope that's a start, at least.
February 24, 2006
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