Canon PowerShot Pro90 IS Review
Aperture Priority Mode
Aperture priority is where you designate the aperture and the camera calculates the best shutter speed, if the exposure is outside of the cameras range (either over or under exposing) the nearest shutter speed will display in red on the LCD screen. Used properly Aperture Priority can be invaluable as it has a direct effect on depth of field (the distance in front and behind the focal point which will be in focus when taking the shot).
The Pro90 has a good range of available apertures:
- Wide: F2.8, F3.2, F3.5, F4.0, F4.5, F5.0, F5.6, F6.3, F7.1, F8.0
- Tele: F3.5, F4.0, F4.5, F5.0, F5.6, F6.3, F7.1, F8.0
Aperture Priority is an exposure mode is accessed by turning the exposure dial to Av. You can change aperture by pressing the left or right arrow keys on the 4-way controller. A basic example of aperture priority is shown below for more read my digital photography glossary:
|F2.8, 1/20s - Less depth of field||F8.0, 1/2 s - Maximum depth of field|
Other manual exposure modes include shutter priority and full manual exposure.
Bracketing is the automatic exposure of an odd number of frames, typically three or five, over and under exposed by equal steps to enable the photographer to select the best exposed frame at a later time. The Pro90 supports bracketing of three shots at either +/- 0.3, 0.7, 1.0, 1.3, 1.7 or 2.0 EV from the metered exposure, it takes the normal shot first followed by the under then over exposed shots. This option is available in P, Tv (Shutter Priority) and Av (Aperture Priority) exposure modes. The sample bracketed sequence below was shot with 0.7 EV setting.
| 1/500s, F6.3
| 1/500s, F8.0
(-0.7 EV exposure)
(+0.7 EV exposure)
The Pro90's built-in panorama mode named "Stitch Assist" is designed to be used with the provided Photo Stitch Software, essentially you can take a panorama (left-right, right-left, up-down, down-up) or 2 x 2 square, the LCD becomes a guide showing a reduced size image preview against the previously shot images. For stitching the images together later I have a personal preference for PanaVue ImageAssembler over the supplied Canon Photo Stitch software (your mileage may vary). Note that Stitch Assist locks the exposure of the sequence to the measured exposure of the first frame. The image below was created by stitching (with PanaVue ImageAssembler) a sequence of three images taken in Stitch Assist mode.
The Pro90's built-in flash range is rated as Wide: 0.7 m - 4.2 m, Tele: 1 m - 3.4 m. It's of the same E-TTL variety as found in the G1 and D30, that means it operates by firing a very brief pre-flash before the main flash, at the time of this pre-flash the camera re-evaluates the flash power for the correct exposure. Note that it's possible to override the default flash power output by +/-2 EV in 0.3 EV steps.
The Pro90 features a movie clip mode which allows for the recording of a maximum 30 second clip (including audio) at 320 x 240, 15 fps. The movie clips themselves are stored in .AVI format using the Motion JPEG Codec (included with the camera). To play the movie below you will need a Motion JPEG Codec or QuickTime 4.0.