Top of camera controls (left) - Exposure Mode Dial

Situated on the top of the camera on the left hand side is the exposure mode dial. This controls exposure operation, be it fully automatic, a preprogrammed scene composition, flexible program, a range of manual and semi-automatic options or one of the three 'camera user' positions. In the user manual Canon breaks these exposure modes into two groups; Basic Zone and Creative Zone. The 50D sees the loss of one of the 40D's custom settings banks (C3), but instead gains Creative Auto (CA) mode. The new mode offers a simplified interface that allows the user to set the exposure in terms of the image results they want, rather than in terms of exposure parameters.

Basic zone exposure modes

Full Auto and the six scene exposure modes are collectively referred to as the 'Basic Zone', in this 'Zone' certain settings are either fixed, limited or unavailable, as shown in this table. Variable settings are detailed in the second table. For the first time, the user can select to shoot RAW files in Basic zone modes.

Fixed settings

Fixed or limited settings

 Unavailable settings
Metering mode (Evaluative) AF mode Custom functions
Color space (sRGB) Drive mode AE lock
Flash compensation (0 EV) Flash mode Bracketing
Exposure compensation (0 EV) Picture Style  
ISO sensitivity (Auto)    
White balance (Auto)    
Focus point selection (Auto)    

In the basic zone the camera will indicate that blur may occur because of slow shutter speeds, it does so by blinking the shutter speed on the LCD panel and viewfinder status bar.

Limited variable settings in Basic zone

Icon Basic zone mode AF
mode		 Drive
mode		 Flash
mode		 Picture Style
Fully Automatic Exposure

Camera has complete control over exposure, point-and-shoot operation. 		AI Focus • Single
• Self-Timer		 • Auto
• Red-eye		 Standard
Portrait

Apertures are kept as large as possible (small F number) to produce a shallow Depth of Field (blurred background). 		One Shot • Continuous
• Self-Timer 		• Auto
• Red-eye		 Portrait
Landscape

 Apertures as small as possible (large F numbers) for the largest depth of field.		 One Shot • Single
• Self-Timer		 • Off Landscape
Close-up (Macro)

Aperture is kept to a medium setting to ensure the subject DOF is deep enough but the background is blurred.		 One Shot • Single
• Self-Timer		 • Auto
• Red-eye		 Standard
Sports

Shutter speed is kept as high as possible to ensure capture of fast moving objects.		 AI Servo • Continuous
• Self-Timer 		• Off Standard
Night Scene

Allows for slow shutter speeds combined with flash to illuminate foreground and background.		 One Shot • Single
• Self-Timer		 • Auto
• Red-eye		 Standard
Flash off

Disables internal and external flash for taking automatic slow exposures.		 AI Focus • Single
• Self-Timer		 • Off Standard

Creative zone exposure modes

The six exposure modes that include the ones most familiar to the camera's prosumer / professional audience. All menu functions and camera settings are available in these modes and can be used in any combination. In manual exposure modes (Tv, Av, M) you control the shutter speed with the main dial (top) and aperture with the quick control dial (rear), you can reverse the operational direction of these dials with C.Fn IV-4.

Icon
Description

Creative Auto

A new mode in which exposure is set using two sliders - one representing depth-of-field, the other representing brightness, essentially sticking a 'results-orientated' face onto the aperture-priority mode.

Program Auto Exposure (Flexible)

Very similar to AUTO exposure but you have access to all the normal manual controls, can set the ISO, exposure compensation, use AE lock, bracketing etc. Program AE is flexible which means that you can select one of a variety of equal exposures (in 1/3 or 1/2 EV steps depending on C.Fn I-1) by turning the main dial. Example:
       
 • 1/30 F2.8 (metered)
 • 1/20 F3.2 (turn left one click)
 • 1/15 F4.0 (turn left two clicks) etc.

Shutter Priority Auto Exposure

In this mode you select the shutter speed and the camera will calculate the correct aperture for the exposure (depending on metered value; metering mode, ISO). Shutter speed is displayed on the viewfinder status bar and on the top LCD, turn the main dial to select different shutter speeds. A half-press of the shutter release causes the camera's exposure system to calculate the aperture, if it's outside of the camera's exposure range the aperture will blink. You can select shutter speeds from 30 to 1/8000 sec in 1/3 or 1/2 EV steps depending on C.Fn I-1.

Aperture Priority Auto Exposure

In this mode you select the aperture and the camera will calculate the correct shutter speed for the exposure (depending on metered value; metering mode, ISO). Aperture is displayed on the viewfinder status bar and on the top LCD, turn the main dial to select different apertures. A half-press of the shutter release causes the camera's exposure system to calculate the shutter speed, if it's outside of the camera's exposure range the shutter speed will blink. The range of apertures available will depend on the lens used but 1/3 or 1/2 EV steps can be selected via C.Fn I-1.
Full Manual Exposure

In this mode you select the aperture and the shutter speed from any combination of the above (plus BULB for shutter speed, apertures limited by the lens used). Top dial selects shutter speed, rear dial selects aperture. Half-press the shutter release and the meter on the viewfinder status bar and top LCD will reflect the exposure level compared to the calculated ideal exposure, if it's outside of +/- 2EV the indicator bar will blink either + or -.

Automatic Depth-Of-Field AE

In this mode the camera automatically controls the depth of field (via aperture) to ensure that all the subjects covered by the focusing points, from those close to the camera to those far away from the camera remain sharply defined.

Top of camera controls (right)

Top of the camera on the right side is the status panel LCD, directly above this are four buttons; LCD backlight and three control buttons (see below). In front of these is the main dial and shutter release button. Along the rear 'under your thumb' you can see the AF-ON, AE-Lock and focus point selection buttons. Press once and turn a dial to change settings, then half-press the shutter release to return to shooting mode (or press another button).

The function of the three buttons immediately above the status LCD is unchanged from the 40D.

Top panel buttons

The table below shows the relationship between each of the top panel settings buttons and the parameters changed by either turning the main dial (top) or quick control dial (rear).

Button Main dial
 Quick control dial

Metering mode

 • Evaluative (35 zone)
 • Partial (9% of screen)
 • Spot (3.5% of screen)
 • Center Weighted Average

 White balance

 • Auto
 • Daylight
 • Shade
 • Cloudy
 • Tungsten
 • Fluorescent
 • Flash
 • Custom
 • Kelvin temperature (2800 - 10000 K)

Auto focus mode

 • One Shot (focus lock on half-press)
 • AI Focus (locks but monitors movement)
 • AI Servo (continuous predictive focus)

AI Focus mode initially locks just like One Shot mode but monitors the focused subject, if the subject moves it will automatically switch to an AI Servo operation.

Drive mode

 • Single shot
 • Continuous L (3 fps)
 • Continuous H (6.5 fps)
 • Self-Timer 10 sec
 • Self-Timer 2 sec

You can optionally combine self-timer with mirror lockup (to reduce mirror induced vibration) via C.Fn III-6.
ISO sensitivity *

 • Auto
 • 100
 • 200
 • 400
 • 800
 • 1600
 • 3200
 • H1 (6400)
 • H2 (12800) (enabled via C.Fn I-3)		 Flash compensation

 • +/-2 EV
 • 1/3 or 1/2 EV steps (C.Fn I-1)

* Shown in 1-stop steps, 1/3-stop ISO steps can be selected via C.Fn I-2.

Under your thumb buttons (Shooting mode)

Button
Operation
Auto focus start

The AF-ON button allows you to trigger auto focus independently of the shutter release 'half-press'. The EOS 40D is the first EOS x0D series to get the AF-ON button and indeed it's a fairly recent new feature to even Canon's professional EOS-1D series. Note that you can re-program the exact function of the AF-ON button via C.Fn IV-1 or you can switch the AF-ON button and AE/AF lock button via C.Fn IV-2 (all custom functions detailed in the menus section of this review).
AE / FE Lock

Press to trigger automatic exposure and lock the exposure for the next shot. Hold the button to lock the exposure for more than one shot.
AF point selection button

Press to choose a single AF point, turn the main dial or the quick control dial to scroll around the available AF points. Alternatively you can also use the new multi-controller to select a point directly (press the selector for the center point). The exact function of this button can be programmed via C.Fn III-3.

Under your thumb buttons (Play mode)

Button
Operation
Thumbnail index / reduce

If in single view play mode, pressing this button will switch to a 2x2 thumbnail index, press again for a 3x3 index. If already magnified pressing this button reduces magnification level.
Enlarge

Press to magnify the current image, there are fifteen steps up to a maximum magnification of 10x. Once magnified you can use the multi-controller to move around the image.