BetterPhoto Q&A
Category: New Answers

measuring diagram

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April 25, 2007

http://www.betterphoto.com/forms/QnAdetail.php?threadID=17534

I do hope this helps,
Debby Tabb

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April 25, 2007

While you might cherish the ‘Y” diagram lighting pattern, consider that this method was derived as “one size fits all”. In short it’s a poor way to light because it typically yields a flat (low contrast) image devoid of depth perception. Because the photograph is a two dimensional presentation we need shadows to generate contrast necessary to deliver an illusion of depth.

Better way:

Place a lamp as close to the camera lens as possible, at lens height. This will be the fill lamp. Many photographers fail to grasp that you are filling shadows as seen by the camera. In my opinion placing the fill off to the side or up etc. is a major error. OK to move fill lamp as needed up – down – left – right – forward – back, with watchfulness. We move it only to adjust to prevent casting a shadow of the camera or some other thing onto the subject or background.

Next place a second lamp known as the main. It is to be placed high to simulate midday sun. It is placed to enhance the subject’s features. Place far to the side for round face. Place nearer the camera for oval face. Subject with long nose, place to cast short nose shadow, short nose, place to cast long nose shadow etc. This is an art acquired by experience.

Set the main’s brilliance so that arrives at the subject plane, twice as bright as the fill. This is accomplished best by light meter but measurements also work. We start by learning how to achieve a 3:1 lighting ratio. This is the magic value considered most flattering. All you need to do to achieve is to cause the light from the main to arrive at the subject plane, twice as bright as the fill light. Twice as bright means the main transmits one f/stop more light.

Why is this 3:1? Consider if both lamps are rated at 100 watts (think units): 100 units arrive at the subject plane cast by the main. 50 units arrive at the subject place cast by the fill. Frontal areas of the face receive both thus 100 units from the main plus 50 units from the fill equals 150 units are delivered to the forehead and cheeks. Shadows are created by the main. Shadows receive no significant light from the main. Shadows do receive 50 units from the fill. Thus the shadows are only illumined with 50 units of light. Now the ratio you have established is 150:50 like a fraction you can reduce to 3:1.

How to set 3:1 by tape measure: Both lamps are the same brilliance; place the main closer to the subject. Measure fill to subject distance (inches) and multiply by .7 or divide distance by 1.4. The results of this math is the main to subject distance. Lamps placed thus achieve the 3:1 ratio as the main light will arrive twice as bright, at the subject plane as compared to the fill. . If the lamps have a brightness adjustment, place both at same subject to lamp distance and set the fill to 1/2 power.

Now try 5:1 ratio which is more forceful. Fill is set to arrive two stops reduced Achieved by setting the fill to 1/4 power (assumes both at same subject to lamp distance). You can also multiply fill to subject distance by 1.4 and move the fill backwards to achieve 5:1. Why 5:1: 100 units from main + 25 units from fill = 125 units frontal areas. Shadows receive only 25 units. Ratio is 125:25 reduces to 5:1.

I know! Ask me what time it is, I tell you how to make the watch. Boring!

Alan Marcus
ammarcus@earthlink.net

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April 25, 2007

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April 25, 2007