Canon PowerShot Pro 90 IS User Guide

Shooting - Letting the Camera Select Settings   

• The fastest shutter speed for flash synchronization is 1/250 second. The camera

automatically resets the shutter speed to 1/250 second if a faster speed is selected.

• The flash may take up to approximately 10 seconds to charge in some cases.

Actual times will vary according to usage and the battery charge.

• The flash will fire at full strength in   mode.
• The flash will automatically adjust its output in the 

, 

,  , 

,  ,  ,  , 

and 

 modes.

• The flash setting is saved when the camera is turned off in the  , 

, 

 and 

shooting modes.

• The flash will fire twice. A pre-flash will fire just before the shutter closes and will

be followed by the main flash. The pre-flash is used by the camera to obtain the
subject’s exposure data so that the main flash can be set to the optimal intensity
for the shot.

A subject’s eyes can appear red in an image shot with a flash in dim lighting due
to light reflecting back from the eye’s blood vessels, which is known as the red-eye
phenomenon. The red-eye reduction lamp fires a soft pre-flash that causes the
pupils to contract, thereby lessening the chances of the eyes appearing red when
the main flash fires.
 - Tell human subjects to look at the lamp since the function will not have any

effect if the subject is not looking at the red-eye reduction lamp.

 - The effect is made stronger by increasing the room lighting or by approaching

closer to the subject.