Aperture
Aperture determines the amount of light coming in through your lens. You then use the shutter speed to determine how long the light enters. Aperture is also the determining factor when it comes to the depth of field of your photo.
The aperture – the hole in the lens – is indicated by a series of numbers. Here you need to remember that a low number is a large hole and therefore lets in a lot of light.
So an aperture of f2.8 is a larger opening than an aperture of f22. The range of aperture values is as follows:
f/1 | f/1.4 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 | f/32 | f/45 | f/64
Below you see a graphic showing how that would look in your camera.
Each time you close the aperture ring one turn, in photography you speak of 1 stop. So going from aperture f2.8 to aperture f4.0 means 1 stop less light. On your camera, this stop is often referred to as EV (exposure value). Minor corrections to your exposure can easily be made with the Exposure Compensation button (easily recognised by the +/- signs on the camera).
The largest opening or aperture of your lens depends on the lens you are using. For example, if you got the standard lens when you bought your camera, it is often an 18-55mm lens with an aperture value of f3.5-f5.6. That means the largest aperture of your lens is f3.5 (at 18mm) and f5.6 (at 55mm).
Photo above was taken with an aperture of f2.8. You can see that the background is blurred and even the sausage rolls are not all in focus.
If you take the same photo with an aperture of f11.0, you will see a big difference in the depth of field. But all the steps in between also have an effect on the final result.
Aperture and shutter speed are inextricably linked if you work in automatic, aperture priority or shutter speed priority mode. If you reduce the aperture of your lens (i.e. close your aperture 1 stop), your shutter speed becomes slower. And that makes sense if you think about it. The hole through which the light enters becomes smaller, so to get the same exposure, your camera will add a slower shutter speed.
In automatic mode, your camera chooses the optimal combination of aperture and shutter speed itself, based on the light situation at the scene. This may seem ideal, but you also lose control over the end result. The camera assumes a programmed calculation and does not know that you, for example, want a nice, blurred background.
It is therefore preferable not to choose automatic mode, but learn to work with aperture priority or manual mode.
Aperture priority mode on a Canon is Av mode. Nikon is the A mode and that is a similar setting for most cameras. Some cameras have the letter D for aperture.
Depth of field
Apart from controlling the amount of light on your sensor, your aperture also largely determines the depth of field in your photo. But what exactly is depth of field?
In simple terms, depth of field is the area in your photo that is in focus. It is important to remember that the larger the hole in your lens, the smaller the depth of field.
In the example above, the first photo was taken at an aperture of f2.8 and has little depth-of-field. The photo after that was taken at an aperture of f5.6.0 and has a larger depth of field. You can see that the difference between the two is already quite significant.
Apart from aperture, there are a number of other things that also affect depth of field:
- the type of camera (this has to do with the size of the sensor);
- the type of lens;
- the distance to the subject.
In the introduction, I already mentioned something about the different camera types. In short, the size of the sensor in your camera determines the depth of field of your photo. The smaller the sensor, the more depth of field (think compact cameras and phones).
As for the lens, it is important to know that a telephoto lens gives less (shallower) depth of field than a wide-angle lens. If you use an aperture of f8.0 with both, the photo will still look different.
Finally, the closer you get to your subject, the smaller the depth of field will be. A macro lens therefore often has a minimum depth of field which makes it difficult to use such a lens out of hand. One little movement and your photo is out of focus.
In a coming blog post we will focus more on focus on how to get the best results in that area.
