 Sandra Wortmann |
Using Studio Lights Outdoors Does using studio light outside make for a more even lighting on your subjects? I have used my flash for a fill. Thanks! Sandy
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Alan N. Marcus |
Hi Sandra, When shooting outdoors under bright sun, the lighting ratio is too extreme for good portraiture. Lighting ratio is a measurement about the difference in brightness between light and shadow. We generally take measurements using a reflection light meter, noting the different difference highlight vs. shadow. Our hearts desire would be a one f stop difference (100% or 1 f stop) with more light on the forehead vs. cheeks in shadows. The facts are, under bright sun conditions, typically the forehead might read f/16 and the cheek in shadow might read f/5.6 this is a 3 f/stop difference. Often the ratio will be even more extreme causing the shadows to go black (void of detail). Today’s films and digital chips remain substandard to the human eye brain when it comes to the ability to record extremes in dynamic range. Thus we must employ countermeasures. This could be fill flash or reflectors. The idea is to try and illuminate the subject with supplementary frontal lighting. Fill flash can be used to partially illuminate the shadows thus the righting ratio is reduced to a tolerable level. For fill flash the trick is to know the guide number published for your flash equipment. We proceed by placing fill flash at lens height near the camera. Next we need to know the f/number we will be using based on the sunlight exposure. We divide the guide number by this lens-opening f-value. The product is the fill to subject distance needed to cause the fill light to arrive at the subject at the same brilliance as the sun light. Now multiply this distance by 1.4. We place the fill flash at this distance. The result is a 3:1 ratio. Example: Your lens is set to f/8 your flash guide number is 100. Thus: 100/8 = 12.5. This tells us that if we placed the fill 12.5 feet from the subject, the sunlight and the light from the flash arrive at the subject plane at equal intensity. This would result in a 2:1 lighting ratio (too flat). Now multiply the distance, 12.5 x 1.4 = 17.5. The fill set to about 17 feet from subject will yield a 3:1 ratio. This is the ideal ratio for portraiture. Rater than a photographer I am a technocracy so you should consider this as marginal technical advice. Alan Marcus
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John H. Siskin |
Hi Sandy, The reason for taking studio lights outside would be to have more power. So what can you do with more power? Well, you can do flash fill at a lower shutter speed and higher aperture. If you wanted a shot with a sharp image from the strobe and a blurred image from daylight mixed together, this would do it. Alternatively, you could use the extra power to diffuse the light from the strobe. This would make for softer fill light, thus softer transition from light to shadow. This could be very useful. I like to use Norman 200B strobes outside. I get power and portability fromm these units. Thanks, John Siskin
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Jeff Coleman |
Hi Sandy, I think you should take a look at strobistblogspot.com this is a blog written by a PJ about using small flash units off camera, there is a link to the strobist.com flickr group so you can see what a couple of thousand people are doing with off camera flash many out doors. I'll be posting a couple shots here on BP that I did a few days ago. happy shooting Jeff Coleman
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