What’s “A” Mode?

Aperture mode is often the preferred mode of the professional photographer. In aperture mode the photographer sets the preferred aperture value and the camera auto selects the proper shutter speed based on the available light.

Aperture mode gives the photographer full control over one of the most important settings in photography. With it the photographer can choose how much or how little depth of field will be rendered in the photo.

For example using aperture mode the portrait photographer can make a creative decision about how much or how little of the subject’s face will be in focus. Keeping the depth of field shallow by using an aperture setting such as f/2 or f/2.8 (These settings will cause the lens aperture to open fully or nearly fully.) the photographer can draw attention to the focused areas while allowing backgrounds to be rendered blurry.

Same can apply to group shots where in aperture mode the photographer sets the amount to f/11 or f/16 resulting in a shot where everything in the frame is in focus. Landscape artists will often use these sort of settings (which cause the lens’s aperture to close down).

We haven’t talked about ISO (or its equivalent ASA a measure of film speed) yet but it is a critical part of the exposure triangle (again a topic we will go into some depth shortly).

In order for the camera to find a “correct” exposure in any mode the ISO or sensitivity of the sensor needs to be set for the amount of light. Generally I like to set my ISO manually so I can control the exposure being set by the camera by adjusting my aperture in this mode and not having the ISO changing in the background.

Auto ISO while very helpful to get a proper exposure for newcomers can cause unexpected results. Manually setting the ISO for typically 200 for daylight and higher when the light is dimmer will eliminate a lot of surprises.

In aperture mode another component of dialing in the correct exposure is found on the exposure compensation dial. In digital photography (unlike film where we expose to favour shadows) we expose to maintain highlights. In aperture mode we can make these small adjustments by adding or subtracting small amounts of exposure. Often a setting of -0.3 or -0.7 or +0.3 or +0.7 will save “blowing out the highlights” or “blocking up the shadows” and will result in a much better exposed image.

So should you use aperture mode all the time? Not necessarily. Some times when focus stacking (another topic for another day) or shooting panoramas (done by shooting a series of vertical images and pasting them together in software) it’s better to shoot in manual mode (which we will talk a lot about soon).

In addition the advantages we’ve already discussed aperture mode is great for street photography where the light conditions are constantly changing. Having the camera continually adjusting the exposure can save a lot of images from over or under exposure. It’s also faster and that’s why a lot of pros shoot almost exclusively in aperture mode.