ChApter 3. Controlling exposure
102 For more on textbooks in digitAl photogrAphy, visit http://www.photoCourse.Com
When you fill the
viewfinder or metering
area with a gray
card and press the
shutter button halfway
down, your camera
will indicate the best
exposure regardless of
how light or dark the
scene is.
PlACing A VAlue
If you have ever seen an original Ansel Adams print, you probably marveled
at the way he used the entire tonal range to capture detail in both the high-
lights and shadows. His prints reflect the incredible control he had over his
images using the Zone System he developed. By exposing and developing
the film correctly, he could expand or contract the tonal range of the nega-
tive to match the tonal range of the scene. Although Ansel‘s system was very
scientific and quite technical, much of what he was able to accomplish can
be accomplished with a digital camera and a photo-editing program such as
Lightroom or Photoshop. Ansel’s system is based on the general principle
that you expose for the shadows and develop for the highlights. In digital
photography, you expose so pixels aren’t clipped and many cameras, includ-
ing all SLRs, display a histogram so you can confirm that you have done this.
You then use a photo-editing program to adjust the tones so they fall in the
desired zones.
To begin, you use exposure compensation to “place a value.” To do this, you
select the most important part of the scene and meter it from close up or use
spot metering mode. The key to metering a specific value is to have the area
of the scene being metered fill the camera’s metering area. You then decide
what tone you want this area to have in the final image. Since autoexposure
will make it middle gray, you may have to change the exposure to move it to
another zone. In manual mode you can do this by changing the shutter speed
or aperture. In other modes, you use exposure compensation to move it up to
two zones in either direction.grAy CArdS
Since the exposure system is designed to set the exposure to capture a middle
gray, Zone V, scene you can get perfect exposures in many situations by using
a gray card. When you fill the viewfinder or spot metering area with a gray
card and press the shutter button halfway down, your camera will indicate
the best exposure regardless of how light or dark the scene is. You can then
use AE Lock to use this setting to take the picture.To guide film
photographers, the
Zone System divided
the gray scale into nine
zones from pure black
to pure white. Each
zone has one stop more
or less exposure than
the ones next to it. The
camera will normally
expose the scene so it is
Zone V.
Zones
0 pure black
I Black with
detail
II textured black
III Very dark gray
IV Dark gray
V middle gray
VI Light gray
VII Very light gray
VIII near white
IX pure white