The built-in flash will not activate for three Basic Zone settings.
The Canon 40D camera contains a built-in flash that pops up to light dark conditions. Certain camera settings on the mode dial prevent this device from lifting and activating. For example, the No Flash setting is especially useful for scenes that prohibit the use of flash photography. A twist of a dial often releases a stationary flash unit. The References includes a Canon EOS 40D Instruction Manual.
Flash Off Mode
The Flash Off mode prevents the built-in flash from popping up. The mode dial's Basic Zone features this setting. The Flash Off symbol displays a white rectangle frame with a bent arrow pointing down. A white diagonal line cuts across the arrow. The flash remains hidden even after depressing the flash button at the front of the camera.
Landscape Mode
The Landscape mode also prevents the flash unit from popping up. The Landscape symbol shows a white cloud hovering over two white mountain peaks on the mode dial. This flash unit lacks the power to provide the correct exposure at a long-distance range. Pressing the flash button on the front of the camera body fails to bring up the flash unit.
Sports Mode
The built-in flash stays stationary with the mode dial set to "Sports." The Sports mode symbol displays a person sprinting to the left. The built-in flash does not pop up when the flash button is depressed. A stronger external flash has a greater chance of lighting moving subjects farther away from the camera.
External Flash Unit
An external flash unit attached to the hot shoe also prevents the built-in flash from popping up. For example, a Canon Speedlite 430EX II set on the hot shoe's flash-synchronization contacts. The Creative Zone modes feature a flash control setting. The menu controls on the camera body's large LCD monitor indicate the conflicting settings. Opening the "Set Up 2" menu and the "Flash Control" menu displays a list of flash options. Selecting the "Built-in flash func. setting" options brings up this warning, "This menu cannot be displayed. External flash is attached."
Solutions
Setting the mode dial to settings other than "Flash Off," Landscape" and "Sports" allows the built-in flash to pop up. Pressing the shutter half-way activates the camera. Pressing the flash button should lift up the flash. Checking and wiping the hot shoe minimizes the chance of something sticking to the external flash detect switch and giving a false warning. This tiny black switch is under the metal spring strip in the right flange of the hot shoe. Turning off the camera, removing the battery, then reinserting the battery after five minutes and turning on the camera resets the camera. Sharp objects should not pry open a stuck flash. Consulting a qualified service center brings you closer to capturing a correctly exposed image.
Tags: built-in flash, flash unit, mode dial, flash button, from popping