Image Processing Reference
In-Depth Information
Lens
Red CCD
Red reflected/filtered here
Only green transmitted
Green CCD
Blue reflected/filtered here
Red & green transmitted
Blue CCD
Half silvered mirror
Figure 6-16
3 CCD camera internal arrangement.
moving images are represented as a series of still frames. Those frames originate from a
variety of sources, not all of which use the same color space.
MPEG is not the same as Motion-JPEG, for example. The Motion Picture Experts
Group (MPEG) incorporates motion-related processing into their standards. This requires
some computation between frames, and each frame is represented by a description that is
meaningful only in the context of its position within a sequence of frames. The Motion-
JPEG format treats each frame as a discrete still picture.
Sequences of images are stored using image formats that are usually considered to
be for still pictures. This is very similar to the way that uncompressed footage is stored.
Color representations other than RGB or luma-chroma are often used.
Table 6-6 describes some alternative still-image formats
6.14
High-Dynamic Range Imaging
Eight bits per color (RGB 24 bit) is simply not enough to represent the full range of tones
in an image. Digital cameras and video systems lose a lot of detail because of this.
Even worse are the hue-shifting effects that you get as a result of gamut clipping.
Shooting directly into the sun shows up in the image as a darkened blotch in the area that
is brightest. The rendered color is some strange hue that seems to bear no resemblance to
the surrounding image. It is like a severe crushing effect on the peak value of the video.
High-dynamic range imaging (HDR) allows a greater range of tones to be stored, and this
leads to better quality video being created after it has been processed.
There is also a correlation among the range of colors that can be represented, what is
available at the source, and what the human eye is able to resolve. In Figure 6-18 the lumi-
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