cgardner
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 p.1 #2 · Help with off camera sb 800s | |
You might find this tutorial of mine helpful: LINK I now use Canon flash, but have used the same technique with others for many years.
Outdoors you have two exposures to contend with. The simplest approach is to start with the flashes off in M mode and first set the ambient background exposure. The caveat is you must keep the shutter below the flash sync speed of the camera (e.g. 1/250th). So on a sunny day your starting baseline for a normally exposed background will be in the range of f/11 @ 1/250th @ ISO 100. If you want darker than normal ambient you must either stop down more (f/16, 22 etc.) or add ND filters to the lens (.30ND = 1 f/stop).
Next you need to realize that overlapping the flash with what you just exposed correctly will blow the highlights. If your goal is to match the range of the scene to the camera sensor the winning strategy is to shoot into the shadow side of the ambient so the flash light doesn't overlap the sunlit highlights and blow them.
Assuming a normal background, with the ambient exposure f/11 on the sunny side, the shady side before adding flash will be - 3 stops, or f/4. Its not totally dark, it is illuminated by the sky. But camera sensor only has a range of about 8 stops total, 6 with detail so the front of the face three stops darker than the highlights will be rendered in a photo much darker than seen by eye in the same light.
Any flash you add will be added on top of the f/4 sky light. How much to add? If you meter from the front side you are measuring sky and flash. If the combined reading is the same as the sunny side, f/11, you'll get a seamless match but loose the perceptual impression of the natural light. It will look flat and fake. So typically the flash is kept .5 to 1 stop below the sunny side.
Next you need to realize you are not adding "fill" in the sense of raising the shadows, but rather adding a highlight pattern on top of the fill. Because the flash is the "key" light it needs to be positioned the same way it is indoors, e.g.; centered an above the face at a 45 degree angle (butterfly pattern) or 45 degrees sideways from the nose for a "short" lighting pattern.
The shadows on the face will remain about the same as they were before flash was added because the flash doesn't hit them. What do you do indoors if shadows are too dark? Add a secondary source of fill. Where should it be placed? Where it will fill EVERYTHING the camera sees and mimic the direction of the natural sky fill: over the lens of the camera. The key light will now be overlapping the both the sky fill and the flash fill coming from the same direction. As indoors the fill would be set below the key light. With fill added from the camera you can dial in whatever tone shadows - and softness - you desire on the face.
Just go out and try it and it will be pretty obvious how it works. Not really rocket science, just common sense application of cause and effect. In practical terms, with a digital camera you can first set the ambient with the camera in M mode and then add the flash visually until you get the results that match your desired result. Even if you meter, you'll wind up chimping and tweeking, so just skipping the metering entirely can wind up being faster (less wandering around with the meter).
Chuck
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