80 Technical Issues: Killing the Gremlins
can be mapped to 16 bits when converted to TIFF format by software
used for raw conversion. This higher bit depth allows for greater image
manipulation later in your image-editing software, without causing
banding or other image-degradation problems. The higher bit depth in
raw fi les also means the full dynamic range of the sensor is preserved,
so it is possible to “recover” burned-out highlights in a raw shot,
whereas it would not be possible to do so in an identical JPEG shot.
“Blah,” I hear some of you say, “JPEG is good enough.” Well, that
is often true. But in many situations, you are much better off with the
raw fi le; so why settle for second best if you have the choice?
Here is some proof. Take a look Figures 5.1 and 5.2, two shots of
a farm building and sky taken by the same camera in sequence using
the same exposure that left the sky about 2.5 stops overexposed.
Figure 5.1 was shot in JPEG and Figure 5.2 in raw. The JPEG image
sky is completely “blown out,” pure white (RGB 255,255,255). There
is nothing I could do to recover any detail in the sky, because there
are no data to manipulate. It is gone forever! The image on the right
looked very similar when opened in my raw conversion software, but
FIGURE 5.1 An overexposed JPEG fi le.