What is Aperture Priority mode?
The next step towards full manual control of your camera is using Aperture Priority mode to take more control over the depth of field in your image. Here’s how it’s done.
Aperture Priority mode is the most useful and convenient mode for shooting many subjects and situations. Changing the aperture gives you control over the depth of field, but the camera will select the shutter speed automatically.
The main advantage of using Aperture Priority mode is that it gives you control over the depth of field in your image, but also with the convenience of not having to set the shutter speed yourself.
Even though in Aperture Priority mode your main concern is the aperture setting, this doesn’t mean you should completely ignore the shutter speed.
The main concern is the shutter speed falling below a speed that you can safely hold the camera steady to avoid camera shake.
In this situation you have a few options: you can either increase the ISO, which will allow you to use a faster shutter speed at the same aperture, or keep the settings the same and use a tripod to prevent camera shake.
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Highs and lows of Aperture Priority mode
You need to keep a close eye on the shutter speed when you are shooting in very dark or bright conditions.
In very bright conditions you need to check that the shutter speed display is showing a speed rather than ‘Hi’, or flashing to indicate there isn’t a shutter speed fast enough to give the correct exposure.
In this case, you’ll have to use a lower ISO, a smaller aperture or reduce the amount of light reaching the sensor by using a Neutral Density filter.
Similarly, in dark conditions the shutter speed display may flash or say ‘Lo’, indicating that there isn’t a shutter speed long enough to avoid under-exposure. In this situation you need to use a wider aperture or increase the ISO until a useable shutter speed is shown on the display.
How to control depth of field in Aperture Priority mode
1 Select the aperture
Set A or Av on the exposure mode dial and use the main input dial to select the aperture. This value will remain even if the camera can’t select a suitable shutter speed, so half-press the shutter to check that a shutter speed is also shown.
2 Apply Exposure Compensation
The metering will automatically adjust the shutter speed, but Exposure Compensation may be needed to increase or decrease the exposure. This will only affect the shutter speed, not the aperture.