Ryan Estrellado

The Canon G9 Series is a group of posts that discuss digital photography techniques and their application on the Canon G9. Feedback, especially from new and veteran G9 users, is welcome.

The first discussion in the Canon G9 Series is about Aperture Priority Mode, noted as Av on the camera’s mode dial.  Much of the information in this post is likely applicable to other point-and-shoot cameras that have Aperture Priority mode, but also includes some specific behaviors I’ve observed when using this mode on the G9.

Before we get into how this mode works on the camera, we’ll first need to define aperture.

What Is Aperture?

Digital Photography School has a very simple and well-presented discussion about the concept of aperture and how it affects the way photographs look:

Put most simply – Aperture is ‘the size of the opening in the lens when a picture is taken.’

When you hit the shutter release button of your camera a hole opens up that allows your cameras image sensor to catch a glimpse of the scene you’re wanting to capture. The aperture that you set impacts the size of that hole. The larger the hole the more light that gets in – the smaller the hole the less light.

Aperture is measured using f-stops.  A lower f-stop indicates a larger opening in the lens and a higher f-stop indicates a smaller opening in the lens.

What does this mean for your picture? Aperture is used to manipulate depth of field, or how far back your camera will bring objects into focus. When the aperture is at its widest setting on your G9, f/2.8, your photo will only bring specific objects into focus while defocusing everything else. When the aperture is at its narrowest setting on your G9, f/8, your photo will not only focus on what is in front of it, but on most of what is behind it as well.

Examples

Let’s look at some photos that demonstrate the different effects achieved when using Aperture Priority mode.

Here’s a picture I took at the widest aperture allowable at that focal length:

Aperture: f/3.5, Focal Length: 18.9 mm

Notice that the object of focus, the toy, appears sharp while everything behind it appears blurry.  The wider aperture allows you to isolate your subject when focusing.  The effect is to draw attention to it while drawing attention away from everything around it.

Here is a picture I took with the narrowest aperture allowable at that focal length:

Aperture: f/8, Focal Length: 7.4 mm

In contrast to the picture of the toy, the flowers in the foreground of this picture are in focus, as are the man in the red shirt and the mountains in the background.  In this way, the long depth of field gives a feeling of vastness to the photo.

When To Use Aperture Priority Mode

With any photo, the depth of field, appearance of motion, and sensitivity to light will be affected by a combination of the aperture, shutter speed, and ISO settings.  When you want to control the depth of field in your photo, the Aperture Priority setting on the G9 allows you to manually set the aperture while letting the camera automatically decide which shutter speed will provide the best exposure for the aperture you selected.  Want to shoot a portrait of your daughter with a sharp image of her face and a nice blurry background?  Use Aperture Priority mode to force the widest aperture possible.  Capturing the vastness of the grand canyon on a family trip?  Set your aperture to the narrowest setting possible to keep everything in focus and let the G9 do the rest.

Aperture Priority on the G9: Things to Think About

There are some other things to keep in mind when using this mode on the G9.  If you are shooting indoors and want a very short depth of field, shooting at a wide aperture such as f/2.8 will result in the camera struggling to find a fast enough shutter speed to prevent motion blurring.  You’ll know this is the case when you see a small icon of a red camera appear on the LCD.  To counter a blurry image, you can select a higher ISO (I suggest no higher than 400 to avoid excessively noisy images) to brighten the image and a tripod to steady the camera for the shot.

You’ll also notice that the G9 will change the maximum aperture possible as you zoom in.  At the shortest focal length, you will be able to shoot at an aperture of f/2.8.  When you zoom in, the camera will change the maximum aperture setting to f/3.2, f/3.5, f/4.0, and f/4.8 as you do so.  This is presumably to reduce the amount of shaking that happens when longer focal lengths are used.

Conclusion

Depth of field is not the only element to consider in a good shot, but it can add a lot of dramatic effect to your photos.  I shoot on Aperture Priority mode often, as it allows me to control the depth of field and makes the Canon G9 automatically do (most of) the rest of the work.  In this way it doesn’t take the spontaneity out of your shooting, as the “no holds barred” approach of Manual mode can sometimes do.  In order to maximize the use of this mode on the G9, practice shooting the same subject while adjusting the aperture, your physical distance from the subject, and the amount you zoom in.  Take note of which factors do what, and which combinations yield the photo you are looking for.

More Reading

Looking for more information?  Read on:

Wikipedia Entry on Aperture

Digital Photography School’s Post on Aperture