As you know (i hope!), we have discussed shutter speed and ISO and how they affect your images. Today, we will look at the final part of the triangle, Aperture. Without doubt, aperture is the most creative of the 3 with shutter speed coming a very close 2nd. Changing your aperture can turn an image from being flat and dull to full of life, dimension and intrigue. So, lets look at what aperture is all about.
Aperture, big or small?
In simple terms, the aperture is the size of the hole in your lens.
When you press the shutter release to take an image, the aperture blades in the lens open up to the size of aperture you have set in your camera. This hole allows light in so the sensor can see the scene or subject you are pointing at.
The smaller the number (e.g. f1.4) the larger the hole and the more light gets in, the larger the number (e.g. f11) the smaller the hole and less light gets in.
Aperture is measured in f stops. Depending on the lens, these can go from f1.0 to around f22. A typical 50mm lens would probably have a range around f1.8 to f22. Moving 1 full stop up or down either doubles or halves the amount of light entering the lens. For instance, going from f2 to f2.8 would halve the amount of light hitting the sensor.
Be aware that changing your shutter speed 1 stop up or down also doubles or halves the light, as does ISO, so if you adjust one, you would need to adjust one of the others in the opposite direction to keep the same exposure. Not many photographers i know make a habit of adjusting ISO regularly (generally preferring to set it once to suit the scene) and mostly just use shutter speed and aperture.
Like with guitars, the top string is at the bottom, the low E is at the top, going up the neck is actually going down towards the body..and so on – aperture has it’s numbers backwards. smaller means bigger. at first it’s confusing but you will soon get the hang of it.
Aperture, the creative side
The main ‘creative’ thing that aperture affects when you take an image is something called depth of field. Depth of field is basically how much of the image is in and out of focus. A small aperture (large F number) will have most, if not all of the image in sharp focus, and a large aperture (small F number) will only have part of the image (wherever you focus on specifically) in focus. Other factors determine how much or how little is in focus for any given aperture, such as subject distance, more on that later.
In the images below, i shot the same scene 4 times with differing apertures. They go in 2 stop intervals from f1.4 to f11 (f1.4, f2.8, f5.6, f11).
Click each image and notice how the background is more and more in focus as the aperture is decreased (larger f number). If the background was closer or i had focussed on something further away, then the background would appear much more in focus.
The best way to learn how aperture control can make such an impact to your images is to go out and experiment. Get yourself in manual control, set the largest aperture your lens has, and shoot something, then shoot it again, reducing your aperture each time. Remember in manual control, you will need to adjust your shutter speed to get the same exposure or you could pop yourself in AV mode – aperture priority – and just adjust aperture, the camera will sort the rest out for you.
Have fun and happy shooting!
