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The aperture determines the amount of light that passes through the lens. Your shutter speed then determines how long that light enters your camera. The aperture also determines the depth of field of your photo.
The low aperture of f3.5 works well here because the focus is on the artichokes.
What does your aperture do?
The aperture – the hole in the lens – is identified by a series of numbers. Remember that a lower number means a bigger hole, and therefore more 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/1.4 | f/2 | f/2.8 | f/4 | f/5.6 | f/8 | f/11 | f/16 | f/22 | f/32 | f/45 | f/64
Each time you close the aperture ring by one f-stop, it is referred to in photography as 1 f-stop. So going from f2.8 to f4.0 means 1 stop less light. On your camera, this is often referred to as an EV (exposure value). Minor corrections to your exposure can easily be made using the exposure compensation button (easily identified by the +/- signs on the camera).
The maximum aperture of your lens depends on the lens you are using. For example, if you got the standard lens when you bought your camera, this is often an 18-55mm lens with an aperture of f3.5-f5.6. This means that the widest aperture of your lens is f3.5 (at 18mm) and f5.6 (at 55mm).
The photo above was taken at an aperture of f2.8. You can see that the background is blurred and even the sausage rolls are not all in focus.
Here is the photo taken at f22
If you take the same photo at f/22.0, you can see a big difference in depth of field. But all the steps in between also affect the final result.
Aperture and shutter speed are inextricably linked when working in automatic, aperture priority or shutter speed priority modes. If you reduce the aperture of your lens (i.e. close your aperture 1 stop), your shutter speed will be slower. And this makes sense when you think about it. The hole through which light enters becomes smaller, so your camera will use a slower shutter speed to get the same exposure.
In automatic mode, your camera chooses the best combination of aperture and shutter speed based on the light in the scene. This may seem ideal, but you also lose control over the final result. The camera makes a programmed calculation and does not know that you want a nice blurred background, for example.
It is therefore better to avoid the automatic mode and learn to work with aperture priority or manual mode.
Aperture priority mode on a Canon is Av mode. On a Nikon it is A mode and this is a similar setting on most cameras. Some cameras have the letter D for aperture.
Depth of field
As well as controlling the amount of light on your sensor, your aperture also largely determines the depth of field in your photo. But what is depth of field?
Simply put, depth of field is the area of your photo that is in focus. The important thing to remember is that the bigger the hole in your lens, the smaller the depth of field.
From 2.8 to 22
In the example above, the first photo was taken at f2.8 and has little depth of field. The next photo was taken at f5.6.0 and has a greater depth of field. You can see that the difference between the two is quite significant.
The last photo was taken with an aperture of f/22.0.
Apart from the aperture, there are a number of other things that 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
I mentioned the different types of cameras in the introduction. In short, the size of the sensor in your camera determines the depth of field of your photo. The smaller the sensor, the greater the depth of field (think compact cameras and mobile phones).
Does every lens give the same result?
When it comes to lenses, it is important to know that a telephoto lens will give less 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 less depth of field you will have. A macro lens therefore often has a minimal depth of field, which makes it difficult to use handheld. A little movement and your photo is out of focus.
