photography: the light meter

2
lights and shadows tend to balance each other out. A center-weighted meter usually works better, because the main subject tends to be near the center of the frame. A spot meter can be very useful, however, when you are photographing a scene in which the light is quite different in different parts of the picture. It can be espe- cially useful when large areas of the picture are either very bright or very dark. When the sun is behind your subject, for example, making the sky very bright and leaving your subject in shadow, you will need to make a spot reading of the subject to be sure that it is correctly exposed. Fortunately, there's an easy way to do this, even without a spot-meter. Simply move close enough so your subject fills most of the frame. Then step back and compose your shot, setting the exposure as indicated by your close-up reading. Some cameras permit you to "lock" the exposure where you want it by pressing a special button. When you use this technique, be sure that you don't create any shadows on your subject when you move in for the close-up reading. Hand-held meters read both re- flected and incident light. For the reflected light reading, you aim the meter's lens at your subject, just as you would with a built-in meter. For the incident reading, you place a translucent cover over the meter's lens, stand near your subject and aim the meter toward your camera or toward the light source. If you're shooting outdoors in even light (either all sunny or all cloudy, for ex- ample), you can obtain an all- purpose average reading by taking an incident reading from the sun. Hand-held meters have one addi- tional advantage. If you attempt to take any photographs in very low light (at night, for example), you may discover that your camera's light meter doesn't work at all shutter speeds. It may shut off when you get down to 1 /8 of a second, perhaps, or 2 seconds. A decent hand-held meter, by contrast, will give you a reading for shutter speeds of 4 minutes or more (depending on the ISO of your film). One final point: as noted in this chapter, reflectance light meters assume that your subject is neutral gray in tone. If you want to photo- graph a subject that is brighter overall (such as a snowy field) or darker overall (such as a black cat), you'll need to change the aperture accord- ingly. If you don't, both the snowy field and the black cat will turn out gray . . . which is probably not what you want. For the snow scene, you'll need to use a larger aperture than in- dicated, and for the cat you'll need to use a smaller one. USING A LIGHT METER The specific gray that a light meter assumes you want is one that re- flects only about 18% of the light it receives from the sun. (Pure white reflects close to 100%; pure black close to 0%.) This figure-"18% gray" —has been scientifically cal- culated to represent average light- ing for most scenes. So, if the average light reaching the light meter is darker than an 18% gray, the light meter will recom- mend a larger aperture or a slower shutter speed, to let more light in. If the average light reaching the meter is brighter than an 18% gray, the meter will call for a smaller aperture or faster speed, to let less light in. Nine times out of ten, this is precisely the kind of advice you want. The light meter will recommend the camera setting you'd choose your- self, if you took the time to figure it out. Ah, but what about that one time out of ten when the light meter's ad- vice is not what you want? Suppose you're photographing someone who is standing between you and the sun. Because the sunlight is coming right at you, it is very bright. Unless the person is filling up most of the frame, your light meter will react to the bright sunlight and tirge you to select a very small aperture or a very fast speed. What will it do to your photograph? By letting only a little light into the camera (just enough so the sunlight shows up as a nice gray), the person you intended to photograph will look like a black blob. This is probably not the effect you hoped for. Here's another example: You're photographing a black cat on a black Light 121

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A view of the light meter

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Page 1: Photography: The Light Meter

lights and shadows tend to balanceeach other out. A center-weightedmeter usually works better, becausethe main subject tends to be near thecenter of the frame. A spot meter canbe very useful, however, when youare photographing a scene in whichthe light is quite different in differentparts of the picture. It can be espe-cially useful when large areas of thepicture are either very bright or verydark. When the sun is behind yoursubject, for example, making the skyvery bright and leaving your subjectin shadow, you will need to make aspot reading of the subject to be surethat it is correctly exposed.

Fortunately, there's an easy way todo this, even without a spot-meter.Simply move close enough so yoursubject fills most of the frame. Thenstep back and compose your shot,setting the exposure as indicated byyour close-up reading. Some cameraspermit you to "lock" the exposurewhere you want it by pressing aspecial button. When you use thistechnique, be sure that you don'tcreate any shadows on your subjectwhen you move in for the close-upreading.

Hand-held meters read both re-flected and incident light. For thereflected light reading, you aim themeter's lens at your subject, just asyou would with a built-in meter. Forthe incident reading, you place atranslucent cover over the meter'slens, stand near your subject and aimthe meter toward your camera ortoward the light source. If you'reshooting outdoors in even light(either all sunny or all cloudy, for ex-ample), you can obtain an all-purpose average reading by taking an

incident reading from the sun.Hand-held meters have one addi-

tional advantage. If you attempt totake any photographs in very lowlight (at night, for example), you maydiscover that your camera's lightmeter doesn't work at all shutterspeeds. It may shut off when you getdown to 1 /8 of a second, perhaps, or2 seconds. A decent hand-held meter,by contrast, will give you a readingfor shutter speeds of 4 minutes ormore (depending on the ISO of yourfilm).

One final point: as noted in thischapter, reflectance light metersassume that your subject is neutralgray in tone. If you want to photo-graph a subject that is brighter overall(such as a snowy field) or darkeroverall (such as a black cat), you'llneed to change the aperture accord-ingly. If you don't, both the snowyfield and the black cat will turn outgray . . . which is probably not whatyou want. For the snow scene, you'llneed to use a larger aperture than in-dicated, and for the cat you'll needto use a smaller one.

USING A LIGHT METER

The specific gray tha t a light meterassumes you want is one that re-flects only about 18% of the l igh t itreceives from the sun. (Pure whitereflects close to 100%; pure blackclose to 0%.) This figure-"18%gray" — h a s been sc ien t i f ica l ly cal-culated to represent average light-ing for most scenes.

So, if the average l ight reachingthe light meter is darker than an18% gray, the light meter will recom-mend a larger aperture or a slowershutter speed, to let more light in .If the average light reaching themeter is brighter than an 18% gray,the meter wi l l call for a smalleraperture or faster speed, to let lesslight in.

Nine times out of ten, this isprecisely the kind of advice you want.The light meter will recommend thecamera setting you'd choose your-self, if you took the time to figureit out.

Ah, but what about tha t one timeout of ten when the l ight meter's ad-vice is not what you want? Supposeyou're photographing someone whois standing between you and the sun.Because the sunlight is coming rightat you, it is very bright. Unless theperson is filling up most of the frame,your light meter will react to thebright sunlight and tirge you to selecta very small aperture or a veryfast speed. Wha t will it do to yourphotograph?

By lett ing only a li t t le light into thecamera (just enough so the sunlightshows up as a nice gray), the personyou intended to photograph will looklike a black blob. This is probably notthe effect you hoped for.

Here's another example: You'rephotographing a black cat on a black

Light 121

Page 2: Photography: The Light Meter

couch. The average light in the sceneis quite a bit darker than an 18%gray. Your light meter will tell you touse a very large aperture, or a slowshutter speed, or both. The result? Awashed-out looking gray cat on agray couch.

None of this means that a lightmeter is a bad thing. A light meter isa great tool. Its primary drawback isthat it wants to make everything gray.Knowing this can help you use itmore effectively. If you're shootingunder tricky lighting conditions (anyconditions in which precision is im-portant), take a meter reading offsomething that is close to an 18%gray, and set your camera accord-ingly. Your blacks will be black, andyour whites will be white. If you wantto make the photograph darker orlighter than "normal," you can thenadjust your aperture or shutter speedaccordingly. If , for example, youdecide that you'd like the whole sceneto appear darker than it actually is,you can take a reading for an 18%gray and then decrease the apertureby one or two stops.

Fine, but how are you supposedto find a sample of 18% gray whenyou need it? You can buy a 18%gray card that is scientifically pro-duced to be exactly 18% gray.Or you can use the gray card youalready have: the palm of yourhand. Whether you're black, white,hispanic or oriental, you can ob-tain an acceptably accurate mid-range reading simply by holdingthe palm of your hand in the lightand aiming a meter at it.

When you do this, be sure that thelighting on your palm is the same asthe lighting on the subject of yourphotograph. Your hand should beheld so that the light strikes yourpalm at the same angle as it strikes

122 The Photographic Eye

By metering off the subject's face, rather than averaging the entire scene, arich black context was produced for this striking portrait. (Studentphotograph.)

your subject. Don't let the cameracast a shadow on your palm. Also besure to hold your camera closeenough to ensure that other light isnot confusing the reading. Mostmodern cameras have center-weighted averaging meters. Thismeans that they read light fromseveral points around the image area,but give more importance to the

reading at the center. Therefore, yourpalm should fill most of the imagearea, and should especially cover thecenter.

(Note: To increase the precision ofyour "palm readings," comparethem to readings from a gray card.Place it in open shade and take a lightmeter reading from it. Be sure thatthe card fills your view-finder. Then

122 The Photographic Eye