Canon EOS 40D Instruction Manual page 31

About the Image Stabilizer Lenses
If an Image Stabilizer (IS) lens is attached and the lens IS switch is set
to <1>, the Image Stabilizer will operate when you press the shutter
button halfway. When the image in the viewfinder looks steady, take the
picture.
For bulb exposures, set the IS switch to <2>. If it is set to <1>, the
Image Stabilizer may malfunction.
The Image Stabilizer continues to operate for about 2 sec. after you let
go of the shutter button. Do not detach the lens during this time. Doing so
may cause a malfunction.
Using the Image Stabilizer will decrease the number of possible shots
(shorter battery life).
Manual Focusing Subjects at Infinity
To manual focus a subject at infinity, look through the viewfinder. If you
just turn the focusing ring all the way to infinity, it might not attain proper
focus.
Do not look at the sun through any lens. Doing so may cause loss of vision.
Image Conversion Factor
Since the image size is smaller
than the 35mm film format, it will
look like the lens focal length is
increased by 1.6x.
Mounting and Detaching a Lens
Image size
(22.2 x 14.8mm / 0.87 x 0.58 in.)
35mm image size
(36 x 24mm / 1.42 x 0.94 in.)
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