 BetterPhoto Member |
Lighting Ratios I am trying to understand how to get lighting ratios of 3 to 1 - 4 to 1, etc., etc., etc. I realize this can all be done with a light meter. I would like to see a chart that shows what f4 to f5.6 translates into the lighting ratio, for example. There must be a chart set up like the old multiplication tables that you could look down the columns and rows and get the ratio. I am using continuous lighting presently to learn different effects of positioning. Using the same wattage lamps 500w for main and fill and 250w for hair.
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BetterPhoto Member |
Nick I am not aware of a chart for lighting ratios, but ratios are quite simple. I also think that there is only a couple of ratios that are of use in photography. I do not know your skill level, so excuse me while I explain this as a beginner. Between the f/stops of 4 and 5.6 you have double or half in the amount of light going through the lens, depending whether you are going from 4 to 5.6 or the other direction. We just call them stops, referring to f/stops. Ratios are explained as ratios and more commonly as stops, like f/stops. A 2:1 ratio means that the shadow side of your subject has one stop less light, or half, hitting it than the key light side. 3:1 is 2 stops, 4:1 is 3 stops. Anymore than that, and you really have no detail left in the shadows to worry about. Film cannot record any detail in the shadows at that ratio, and digital is getting iffy. If you are using hot lights and bouncing them out of umbrellas, when you move your fill light back to increase your ratio, you also change the light quality because your large umbrella becomes a small umbrella in relation to your subject. I rarely use hot lights, preferring strobes instead, but I have built units to control the output of hot lights so I do not have to move them in or out to control ratios. I bought an electrical outlet box, a dimmer switch, and an electrical outlet and wired it all into the box with a short extension cord. I then plug the hot light cord into the outlet and use the dimmer switch to increase or decrease power to the hot light and the brightness adjusts as well. This helps control the ratio without moving the light. Problem is that as you dim the light, it changes the Kelvin temperature and makes the light warm up.
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Kerry L. Walker |
First, I would like to suggest that you stick with a 2:1 ration if you are using clolor film. Most color film has a 1 stop latitude for underexposure. After that, you will lose detail in the shadows. B&W film has a greater latitude for underexposure so you can use a 3:1 or even 4:1 and maintain some detail in the shadows. To get a 2:1 ratio with lights of equal intensity, simply place the fill light 1-1/2 times further away from your subject than your main. Note that light falls off geometrically. If you are 1.5 times as far away, your light intensity has dropped by about 2 (1.5 x 1.5=2.25). If it is twice as far away, you light intensity has droped by 4 (2x2=4).
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Carolyn O'Leary |
Nick, One of the responses to your question wasn't quite right. The f-stops on your camera lens represent a doubling or halfing of the light that reaches the film, for example f8 would allow in twice the light that f5.6 would. So if you have a main light that you have metered at f8 and then you turn off this light and meter your second (fill) light and get 5.6 you have a 2:1 ratio because the main light is producing twice as much light as the fill light. If you have a 2 stop difference in your readings, this means 4 times as much light from your main light so a 4:1 ratio, 2x2=4. If there is a 3 stop difference you have a lighting ratio of 8:1, 2x2x2+8. Here is a chart that will make sense once you see how the numbers relate to each other. 1:1 = 0 stops 128:1 = 7 stops
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