6.8 Rapid Exposure Adjustments

During intense shooting situations, it can be important to be able to very rapidly adjust exposure.  This is true whether you’re using manual exposure or one of the automatic exposure modes.  A very common scenario is one in which the bird or birds you’re working keep moving in and out of the shade.  In a complex environment, the shady areas may be extensively interspersed with the sunny areas, so that movement of the bird between shade and sun may happen every few seconds.  Although spot metering may work well for you in some of these situations, in others you may find that the metering sensor is larger or smaller than the bird, so that the meter reading is affected by other parts of the scene besides the bird.  I’ve had little luck with spot metering, especially for small birds such as warblers, and have therefore tended to opt for either evaluative/matrix metering coupled with aperture-priority (Av) exposure mode, or more recently by simply using fully manual mode most of the time (and disregarding the meter reading).



    When using evaluative metering and automatic exposure (Av or Tv), changes to the exposure level can be made very rapidly via exposure compensation (EC) settings, as long as the EC is mapped to a conveniently accessible dial or other control on your camera (such as a joystick or pair of buttons).  After taking a shot and then quickly glancing at the image as it briefly displays on the camera’s LCD, you may decide to dial in a +1 or -1 adjustment on the EC control before taking the next shot.  Typically you’ll only need to make a few such adjustments before getting the exposure you want—as long as the bird doesn’t move from the sun to the shade (or vice versa).  Once you’ve found a suitable EC setting—say, -2 for example—that works well while the bird is in the sun, you can then concentrate on finding a setting that works well when that bird moves into the shade.  Suppose that +3 works well in the shade for this particular bird.  Making a mental note of these two settings—+3 for the shade and -2 for the sun—will allow you to more efficiently work this particular bird for the duration of the shoot.  Every time the bird moves from the sun to the shade, you can simply turn the EC dial 5 clicks—from -2 to +3—without taking your eye from the viewfinder.  When it moves back into the sun, you turn the dial 5 clicks in the other direction.  As long as you don’t accidentally turn the dial the wrong number of clicks, or in the wrong direction, this strategy can be very quick and very effective. 



    The same strategy works in manual mode, except that you need to select one or more parameters—aperture, shutter speed, or ISO—to swap between the sunny and shady scenes (or when rapidly switching between a light-colored bird and a dark one).  The selection of parameter(s) to adjust is often dictated for you by the shooting scenario.  If, for example, your shutter speed is already at the lower limit for eliminating motion blur, and your aperture is already wide open (or as wide as your lens can open without compromising sharpness), then you’ll probably want to stick to adjusting ISO—taking care, of course, not to increase the ISO to such a high value that your image is excessively noisy.
    Regardless which exposure mode you use, it’s best if your camera allows you to re-map the exposure controls (such as EC, ISO, etc.) to the most accessible dial on your camera, as noted earlier in this chapter.  My current camera has two dials, one on top next to the shutter release, and one on the back next to the LCD.  Since adjusting the top dial requires taking my index finger off of the shutter release, I prefer to make most of my adjustments with the back dial, since my thumb is always free to adjust that.  Thus, whichever parameter (ISO, aperture, shutter speed) I’m modifying the most in a particular shooting scenario is the parameter that I map to the back dial.  That way I can adjust the exposure without having to lift my finger off the shutter release, which is useful when using the focus-and-recompose method (or when tracking a bird in continuous AF mode).  People who are especially coordinated may be able to operate the shutter release with the middle finger, the top dial with the index finger, and the back dial with the thumb, all at the same time.

    Finally, note that making adjustments to exposure becomes more complicated when using flash, since flash violates the rule of reciprocity mentioned earlier.  Furthermore, in flash photography we have to manage not only the overall exposure level, but also the flash ratio—that is, the ratio of flash light to ambient light (from the sun).  These issues are addressed in detail in Chapter 7.