Pentax K200D - Manual (Page 17)

Before Using Your Camera
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Shake Reduction (SR)
Shake Reduction (SR) on the x features a PENTAX original
system which uses magnetic force to move the image sensor at high
speeds, compensating camera shake.
The camera may generate some operating noise when it is shaken, such
as when changing the composition of a picture. It is not a malfunction.
The captured area (view angle) will differ between the x and 35 mm
SLR cameras even if the same lens is used because the format size for 35 mm
film and CCD are different.
Sizes for 35 mm film and CCD
35 mm film : 36×24 mm
x CCD
: 23.5×15.7 mm
Angles of view being equal, the focal length of a lens used with a 35 mm camera
must be approximately 1.5 times longer than that of x. To obtain an angle
of view framing the same area, divide the focal length of the 35 mm lens by 1.5.
Example) To capture the same image as a 150 mm lens attached to a 35 mm
camera
150÷1.5=100
Use a 100 mm lens with the x.
Inversely, multiply the focal length of the lens used with x by 1.5 to
determine the focal length for 35 mm cameras.
Example) If 300 mm lens is used with x
300×1.5=450
Focal length is equivalent to a 450 mm lens on a 35 mm camera.