Canon PowerShot A70 Review: 5. Operation & Controls: Digital Photography Review

Top of camera controls

The top of the A70 has three control groups, firstly the on/off button, this requires a short hold before the camera will power on, power off is instant. The mode dial overhangs the rear of the camera slightly making it relatively easy to change mode, the action of the dial is just stiff enough so as not to suffer accidental change. At the front you can see the zoom lever and shutter release button.

Zoom Lever (Record mode)

	Zoom telephoto Zooms the camera's lens towards the telephoto, maximum optical zoom of 105 mm (35 mm equiv.). A full zoom from wide to tele takes 2.0 seconds. There are 7 zoom steps from wide angle to telephoto. If the camera is already at maximum optical zoom and digital zoom is enabled the camera will apply increasing levels of digital zoom (indicated on the LCD monitor).
	Zoom wide angle Zooms the camera's lens towards the wide angle of 35 mm (35 mm equiv.). A full zoom from tele to wide takes 2.0 seconds. There are 7 zoom steps from telephoto to wide angle.

Zoom Lever (Play mode)

	Image magnify (zoom in) Magnifies the displayed image, a range of magnification is available from 2x up to 10x. Magnifying the displayed image is very fast.
	Thumbnail index / (zoom out) Switches to a 3x3 (9 image) thumbnail index, use the four direction buttons on the rear of the camera to move around the index. If the displayed image is magnified pressing the zoom lever towards wide zooms out of the magnification.

Exposure Modes

	Automatic Exposure Camera has complete control over exposure, point-and-shoot operation, the majority of manual features are disabled, you can't alter white balance, exposure compensation, ISO, metering or use manual focus. You can set flash mode, drive, macro focus and image size.
P	Program Auto Exposure Very similar to AUTO exposure but you have access to all the normal manual controls such as ISO sensitivity, exposure compensation, white balance, manual focus etc.
Tv	Shutter Priority Auto Exposure In this mode you select the shutter speed and the camera will attempt to select the best aperture for a proper exposure. Shutter speed is displayed on the LCD, press the left / right arrows to select different shutter speeds. A half-press of the shutter release causes the cameras exposure system to calculate the aperture, the LCD view changes to reflect the look of the final image. If the exposure is outside the cameras exposure range the aperture will appear in RED. Available shutter speeds: * Note: Aperture / shutter speed rule, below 1/2000, 1/1600 1/1250, 1/1000, 1/800, 1/640, 1/500, 1/400, 1/320, 1/250, 1/200, 1/160, 1/125, 1/100, 1/80, 1/60, 1/50, 1/40, 1/30, 1/25, 1/20, 1/15, 1/13, 1/10, 1/8, 1/6, 1/5, 1/4, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 1.3, 1.6, 2, 2.5, 3.2, 4, 5, 6, 8, 10, 13, 15 secs (Shutter speeds of 1.3 seconds or slower will enable the cameras noise reduction system).
Av	Aperture Priority Auto Exposure In this mode you select the aperture and the camera will attempt to select the best shutter speed for a proper exposure. Aperture is displayed on the LCD, press the left / right arrows to select different apertures. A half-press of the shutter release causes the cameras exposure system to calculate the shutter speed, the LCD view changes to reflect the look of the final image. If the exposure is outside the cameras exposure range the shutter speed will appear in RED. Available apertures: * Note: Aperture / shutter speed rule, below Wide: F2.8, F3.2, F3.5, F4.0, F4.5, F5.0, F5.6, F6.3, F7.1, F8.0 Telephoto: F4.8, F5.6, F6.3, F7.1, F8.0
M	Full Manual Exposure In this mode you select the aperture and the shutter speed from any combination of the above. Left and right arrows change either shutter speed or aperture, press SET to switch between the two. When you half-press the shutter release the camera meters the scene and displays a numeric indication of how far over or underexposed the image is (compared to its metering). This value is in EV's (exposure value / stops), if the exposure is under or overexposed by more than 2 EV's the camera simply displays -2 or +2 in red. During the half-press the LCD view changes to reflect the approximate look of the final image.
	Portrait In this mode apertures are kept as large as possible (small F number) to produce a blurred background to help define the subject in a portrait shot. Note: Macro and manual focus are available in Portrait mode.
	Landscape In this mode the flash is by default disabled (although you can enable it) and focus is locked at infinity. Apertures are kept as small as possible (large F numbers) to produce the largest possible depth of field. Manual focus is available. Designed to be used for taking landscape shots.
	Night Scene Known on other cameras as "Slow Sync Flash". Put simply in this mode slow shutter speeds are used to capture a dimly lit background (buildings at night for example) and the flash fires briefly to illuminate a foreground subject.
	Fast Shutter Instructs the camera to uses the fastest possible shutter speed for a particular exposure, this often means the largest aperture (F2.8 at Wide, F4.9 at Tele) in combination with ISO 100. Useful for capturing sports events.
	Slow Shutter Instructs the camera to uses the slowest possible shutter speed for a particular exposure, this often means the smallest aperture F8.0. Useful for blurring moving water.
	Stitch Assist Designed to make shooting of panorama / stitch shots easier. You have a choice of five different stitch modes: left-right, right-left, down-up, up-down or 4-frames in a square. The display changes to show previously shot frames in the sequence to help alignment of each frame. Exposure and White Balance are locked to the first frame.
	Movie Mode Record short movie clips, you can not zoom during movie recording and the exposure is locked from the moment you start recording. • 640 x 480, 15 fps, up to 30 secs (inc. audio) • 320 x 240, 15 fps, up to 3 mins (inc. audio) • 160 x 120, 15 fps, up to 3 mins (inc. audio)

* Aperture / Shutter speed rule

Just like other PowerShot's (and many other digital cameras) the A70 is limited by the fact that it uses a single iris mechanism for both aperture and shutter. The iris opens at the beginning of the exposure to a certain size for the selected (or metered) aperture and then closes again at the end of the exposure. The speed at which the iris can go from a wide aperture to completely closed creates a limitation as to the maximum shutter speed available at different apertures.

Zoom position	Aperture	Max. Shutter Speed
Wide angle	F2.8	1/1250 sec
	F3.2 - F4.0	1/1600 sec
	F4.5 - F8.0	1/2000 sec
Telephoto	F4.8	1/1250 sec
	F5.6 - F7.1	1/1600 sec
	F8.0	1/2000 sec

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