2.5. Light Metering Tricks There are all sorts of ways to measure exposure. You can use one of your camera's metering modes in P shooting mode or (better yet) bracket a sequence of shots in half stop increments. You can look at the actual photo on your preview monitor after you shoot the test. Most cameras will also show you the exposure if you tell them to "show info." So, just pick the shot in your sequence that has the best exposure, get the info, switch to M mode, and set the exposure accordingly. Or you can shoot a gray card in spot metering mode. This ensures that you're only metering the image's midtones, so you should get the best compromise in exposure for all the prevailing levels of brightness. Your camera's color balance is calibrated at the same time, so you can set the white balance for all these exposures with one of the White Balance droppers that are available in both Photoshop and Camera Raw. In Photoshop Elements 4, you can only use an eyedropper to set white balance by choosing a Levels Adjustment Layer from the Layers palette. If the result is too much or too little brightness, you'll have to correct it by adjusting the midtone slider in the RGB channel (see Chapter 5). 2.5.1. Types and Uses for External Meters Although you can preview a shot and adjust your exposure according to the exposure information for that shot, there are times when an external meter can save time. That's because you can read for proper exposure before you start taking pictures. Also, most meters read exposure in such a way that you see a variety of aperture and shutter speed combinations that allow the transmission of equal amounts of light to be recorded by your sensor. That way, you don't have to do calculations each time you switch to manual mode but want to use a different shutter speed and aperture combination (see Table 2-1). Table 2-1. A chart of equivalent f-stop and shutter speeds at ISO 100 in average daylight. For each doubling of ISO speed, decrease the f-stop by raising it to the next highest number in the chart. Most digital cameras allow you to adjust both shutter and f-stop in half-stop increments.1/8 sec | 1/15 | 1/30 | 1/60 | 1/125 | 1/250 | 1/500 | f-16 | f-11 | f-8 | f-5.6 | f-4.0 | f-2.8 | f-2 |
There are two types of meters that might come in handy: Incident and Spot.
Incident light meters These meters are held in the area that is the center of interest and are pointed toward the camera. You set the ISO on the meter that will be the same ISO for your camera. You then press a button and the range of alternative exposures in Table 2-1 suddenly appears. Gossen makes an incident light meter that can measure either available light or strobe. You can see an incident light meter in Figure 2-9. Figure 2-9. An incident light meter being held as it is used to measure exposure.
Spot meters Spot meters that aren't built-in generally look a bit like miniature telescopes and can be used to measure a small portion of the subject, even if it's too far away to get close to. If you frequently use long telephoto lenses, you might want to consider an external spot meter. However, if you shoot with a camera back or a DSLR, your built-in meter is measuring an area that is always within the angle of view for that particular lens. So there's far less need for a spot meter. Table 2-2 shows the ISO ranges of several popular DSLR camera models. Table 2-2. A chart showing the actual ISO ranges of several DSLR cameras.Canon 350D | | 100 | 200 | 400 | 800 | 1600 | | Canon 20D | | 100 | 200 | 400 | 800 | 1600 | 3200 option | Canon 5D | 50 option | 100 | 200 | 400 | 800 | 1600 | 3200 option | Canon 1DS Mk II | 50 option | 100 | 200 | 400 | 800 | 1600 | 3200 option | Nikon D2X | | 100 | 200 | 400 | 800 | 1600 option | 3200 option | Nikon D200 | | 100 | 200 | 400 | 800 | 1600 | 3200 option | Nikon D70 | Auto | | 200 | 400 | 800 | 1600 | | Nikon D50 | Auto | | 200 | 400 | 800 | 1600 | | Olympus E-500 | Auto | 100 | 200 | 400 | 800 option | 1600 option | | Olympus | Auto | 100 | 200 | 400 | 800 option | 1600 option | | Pentax DL | Auto | | 200 | 400 | 800 option | 1600 | 3200 | Pentax DS2 | | | 200 | 400 | 800 option | 1600 | 3200 | Fuji S3 Pro | | 100 | 200 | 400 | 800 | 1600 | | Minolta 7D | Auto | 100 | 200 | 400 | 800 | 1600 | 3200 | Minolta 5D | Auto | 100 | 200 | 400 | 800 | 1600 | 3200 | Contax | | 100 | 200 | 400 | 800 | 1600 | |
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