Canon 30D - Manual (Page 16)

Page 16 of 35 © Ken Rockwell 2006
SIDE and FRONT CONTROLS
Look for the buttons on the front of the 30D near the lens.
Lightning Bolt Button (just above and to left of EOS 30D label): Press it to
pop up the built in flash. That's all it does. Unlike Nikon, you change the flash
brightness (exposure compensation), if needed, with the flash exposure
compensation button on the top of the camera.
The finder flashes BUSY while the flash recycles.
Big Unmarked Button (middle, to right of "Canon" marking on lens): Press it
to unlock the lens for removal. Hold it in and turn the lens so the red or white
dot goes towards the top of the camera to remove it. To mount another lens
you merely match the red or white dot on the lens with the red or white dot on
the 30D and rotate it until it clicks and locks automatically.
Teeny Unmarked Button (just below Big Unmarked Button): Press and hold
it to preview if the background will come into sharp enough focus to be
distracting. It probably will make the viewfinder get darker, ignore that.
Photographers call this button the "depth-of-field preview button." This button
was important for film cameras, but since you get a better view playing the
image back on the LCD, today this button is for a quick check of the
background when making portraits.