On the top right of the camera we have the exposure mode dial and the main power (on/off) slider switch. The Alpha 900 has dropped the 700's scene modes in favor of direct access to the three user-programmable custom modes.
Auto Program Exposure
This is essentially the camera's "point and shoot" mode. When you select this mode various settings return to their defaults (with most defaulting to 'auto'). However unlike other digital cameras in Auto mode they are not locked and can be adjusted.
Program Exposure (with shift)
Program exposure mode on the A900 can be shifted, this means that you can select one of a variety of equal exposures by turning the control dial, by default the exposure is shifted by shutter speed (indicated as PS), you can choose to shift by aperture (PA) by changing the 'Control dial set' option in the custom menu. If you turn off the direct AE compensation option you can use Aperture or Shutter speed shift by turning the rear or front control dials.
In this mode you select the aperture and the camera will calculate the shutter speed for the exposure (depending on metered value; metering mode, ISO). Aperture is displayed on the viewfinder status bar and the LCD monitor (if recording display is enabled), turn the front or rear control dial to select different apertures. Note that if you have direct AE compensation turned on one of the dials will control AE-C instead.
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 the LCD monitor (if recording display is enabled), turn the front or rear control dial to select different shutter speeds. Note that if you have direct AE compensation turned on one of the dials will control AE-C instead.
Full Manual Exposure
In this mode you select the aperture and the shutter speed (and additionally Bulb shutter). Again by default the front dial controls shutter speed, the rear controls aperture, but this can be flipped using the custom menu. As you turn the dials the EV scale on the recording display and the viewfinder status line indicates how close the selected exposure is to the metered exposure (+/- 3 EV).
Front of camera controls
On the front left of the camera located on the side of the lens mount surround is the Depth-of-Field preview button, which can be used in the conventional 'optical' manner (closing down the aperture) or to activate the new Intelligent Preview function. On the front right of the camera is the lens release button, below this the Focus mode switch which allows you to select between Single, Auto, Continuous and Manual focus modes.