Aperture, Shutter Speed and Focus

APERTURE

As the name suggests, the lens aperture is an opening. This opening is controllable by the photographer who determines whether a lot of light (large aperture) or a little light (small aperture) is to make its way through to the film plane or CCD.

By using the aperture ring, the photographer selects a ‘f-stop’ (f2, f2.8, f4, f5.6, f8, f11, f16, f22 etc), a pre-set opening. Each time you move one stop you either double or halve the amount of light coming through, depending on whether you are ‘opening up’ or ‘stopping down’. The smaller numbers (f2, f2.8 etc) are actually bigger openings and the bigger numbers (f16, f22 etc) are smaller openings. That’s about as complicated as it gets too. This halving or doubling relationship is very important and makes life very easy when dealing with shutter speeds.

SHUTTER SPEEDS

Between the aperture and the film or CCD is the shutter. The shutter speed determines how long the light being let in by the aperture gets exposed to the film or CCD.

Where it all fits together beautifully, is that a change from one shutter speed to the next either halves or doubles the time of the exposure. Sound familiar?

WHAT TO USE

Apertures and shutter speeds give certain looks. Using a large aperture (f2.8, f4 etc) gives what’s known as a shallow depth of field, where only what you focus on is in sharp focus and what is in front of or behind your subject is out of focus. Shallow depth of field is generally used for portraiture.

A small aperture (f11, f16 etc) allows more of the scene in front of and behind your subject to be in focus. A long depth of field is generally used for landscapes.

Shutter speeds can ‘freeze’ the action (think sports) or ‘blur’ part of the scene to indicate speed or movement.

When photographing, try visualising what you want the picture to look like and set your exposure accordingly. What’s in the shot, what are you trying to convey, should you use a long depth of field or a shallow one, do you need to freeze the action, give a sense of movement or simply have a workable shutter speed because you’re hand-holding the camera?

EXPOSURE

Once your basic exposure has been determined (using an on-camera or hand-held meter) you can then adjust either your shutter speed or aperture to better suit your requirements.

Say for example, your camera is telling you that the exposure you need is f8 at 1/125 second. You are taking a portrait shot, however, and only want your subject in focus. An aperture of f8, you decide, will bring too much of the background into focus and you’d prefer to use f4.

By ‘opening up’ the two stops to f4 (f8 to f5.6 to f4) you’ve increased your exposure by two stops. To compensate, you have to decrease your shutter speed by two stops (one stop down is 1/250, another stop is 1/500). In other words, f4 at 1/500 second is the same as f8 at 1/125 sec.

By working up and down the scale, you can work out the other aperture/shutter speed combinations. All will have the same exposure but a different look. And that’s the beauty of photography: in any given situation, you can choose whichever combination suits your needs best.

FOCUS

This is obvious and doesn’t need too much explanation. It is nice to be in control of it and not fight against an auto focus that’s doing its own thing.

The whole point of this exercise is to get a more tactile experience when photographing; to not be guessing at what’s going on but rather knowing.

The best way to achieve this is to switch off all the automated features that do the thinking for you and turn your camera to manual.

Interestingly, all those little icons on your camera dial like a face or a mountain scene or a person running are just telling the camera to prioritise a big aperture, a small aperture and a fast shutter speed respectively. It’s just as easy to do it yourself and be in control of your photography.

Although it may seem daunting at first, in practice using aperture, shutter speeds and manual focus is very simple and infinitely easier to understand than the manuals that come with cameras nowadays. The features are there to sell cameras, not make you a better photographer. Take the unnecessary features away and cameras don’t really need manuals at all.