Canon 500D 用户手册

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Attaching and Detaching a Lens
34
To zoom, turn the zoom ring on the lens 
with your fingers.
If you want to zoom, do it before 
focusing. Turning the zoom ring after 
achieving focus may throw off the 
focus slightly.
While pressing the lens release 
button, turn the lens as shown by 
the arrow.
 
Turn the lens until it stops, then 
detach it.
 
Attach the rear lens cap to the 
detached lens.
To owners of the EF-S18-200mm f/3.5-5.6 IS kit lens:
You can prevent the lens from extending 
out while you are carrying it around. Set 
the zoom ring to the 18mm wide-angle 
end, then slide the zoom ring lock lever to 
<LOCK>. The zoom ring can be locked 
only at the wide-angle end.
About Zooming
Detaching the Lens
 
Do not look at the sun directly through any lens. Doing so may cause 
loss of vision.
 
If the front part (focusing ring) of the lens rotates during autofocusing, do 
not touch the rotating part.
Image Conversion Factor
Since the image sensor size is 
smaller than the 35mm film 
format, it will look like the lens 
focal length is increased by 1.6x.
Image sensor size
(22.3 x 14.9 mm / 0.88 x 0.59 in.)
35mm image size
(36 x 24 mm / 1.42 x 0.94 in.)