Part 5 – Understanding Your Camera

 I’m going back to basics this week. Way back. For those of you who understand the very essential principles of what your camera does when it takes a photo I apologize  Feel free to go look at Jimmy’s blog or a funny cat video on You Tube…whatever. But it’s been my experience that cameras are so easy to use these days on full auto function that many people don’t actually know these fundamentals. If you have a Digital SLR or a compact camera with manual over-rides understanding these simple premises will get you more confident in playing with knobs labelled anything other than P (Program – i.e. automatic) and even if you just have a fully automated point and shoot knowing what your camera is actually doing will help you understand its capabilities better.

Knowledge is power right? So lets focus on the Power of Three;

  1. Aperture
  2. Shutter Speed
  3. ISO

A correctly exposed photograph is a simple combination of aperture, shutter speed and ISO. Since the beginning of photography these three factors have always been at the heart of the matter and they still are today. Up until about 1975 when auto exposure cameras arrived on the scene every photographer had to choose both aperture and shutter speed and the choices he/she made about those were directly influenced by the film’s ISO (or sensitivity to light). Now you can have a fully auto camera or choose P on your combo camera and exactly the same thing happens only the camera does the choosing instead of you.

Like any co-dependent relationship though these three basic factors don’t act in isolation. Anything you do to one affects the other and its the happy marriage of this threesome that gets the result that you want. That being said lets break them down first for a closer look…

  •  Aperture

This is the hole that lets light into your camera via the lens. Think of it like your eye’s iris. Like your iris this hole can be made bigger or smaller depending upon how much light you have available and how much you want to let in to be recorded on the film or nowadays the digital sensor. The aperture size is expressed in ‘f’ numbers like f/4.0, f5/6, f/8.0 and so on. The ‘f’ refers to focal ratio (the ratio of the diameter of the lens aperture to the length of the lens, but that’s not important now.) But as a consequence, rather confusingly the smaller the number the larger the opening is.
Diagram 1 apertures

  •  Shutter

If the aperture is like the iris of your eye then the shutter is like a blink. The shutter speed is the length of time the camera shutter is open to let light in (through the aperture) and onto the digital sensor. They are measured in fractions of a second or whole seconds when they are really slow. ie. 1/500, 1/125, 1/60 or 1s. So 1/500 is a much faster shutter speed than 1/60. In low light situations you may want to let as much light in as possible so a slow shutter speed is good whilst fast shutter speeds are necessary to ‘freeze’ motion and avoid the blur of a fast moving object.

Now it doesn’t take a genius to figure out that if the aperture is really big (or wide as we like to say) something like f2.8, therefore letting a lot of light in, that the shutter speed will need to be fast or the image will be overexposed. And vice versa. So you can start to see how the two are intertwined.

  • ISO

The third of the holy photographic triumvirate is ISO (pronounced ‘eye-so’ rather than ‘eye-es-oh’). This is the level of sensitivity of your camera to available light. Back in the day this was the ‘speed’ of your film and you would have to choose what film to load into your camera depending on what you were going to shoot and the light conditions you were photographing under. Today it’s all done digitally in your camera and should you wish you can change your ISO on every shot. That’s progress.

It is measured in numbers, (expressed in 00‘s), the lower ones meaning lower sensitivity to light and the higher more sensitivity. ISO 100, 200, 400, 800,1600 and maybe more depending on your camera. Each increment makes your sensor twice more sensitive to light. As it becomes more sensitive to light it means you need less available light to get a correct exposure. So your shutter speed can be faster or your aperture smaller (or both). Very handy in certain situations. However more sensitivity comes at a cost – as the ISO increases so does the ‘noise’ or ‘graininess’ of your image. Like many things in photography, it’s a trade off.

That’s all well and good I hear you say, but if my camera can do all this for me why bother to fiddle around with settings and do it myself? And you’d have a point. Fully automatic point and shoot cameras and even posh DSLRS on P will do a more than adequate job of triangulating these three elements, leaving you to worry about the important things like subject matter, composition and light source direction. But while your camera computes, it doesn’t think or know what it is you want to get from the shot. It will not know if you are taking a portrait or trying to get an action shot of a barrel race in the arena. If you have the ability to choose the individual settings you can adjust them to better suit what you are trying to capture with the shot.

For example, aperture size has a critical impact on what we call ‘depth of field’. This is the portion of the scene in your shot which is in focus. When the aperture is wide the depth of field is small (or shallow), meaning that only a small part of the picture is in focus leaving the foreground and/or the background blurry. In shooting portraits this can be a very desirable effect, making the subject stand out better.

Aperture f4.0
Aperture f4.0

Whilst photographing landscapes it is usually better to have a large depth of field with everything in focus. To achieve this a small aperture is better. In each instance your shutter speed will have to adjust to balance the size of aperture. In the landscape situation your shutter speed will need to be slower, which is why you will often see landscape photographers using tripods for their shots as anything slower than 1/60 shutter speed if you are ‘hand-holding‘ your camera will usually result in a bit of a blur or softness in your image.

Shutter Speed 1/25
Shutter Speed 1/25

Shutter speed (coupled with ISO) is very important in action shots. You want a fast shutter speed to ‘freeze‘ the motion and make it look crisp. At least 1/500 and even more if your camera can handle it. This is why action shots need a lot of light. Plenty of natural light if possible, but increasing the ISO will help and of course the aperture will need to assist by being wider to let more available light in. This mean your depth of field will be shallow so you’ll need to be good at focusing on what part of the action subject you want in focus. The opposite is true if you want to photograph a landscape or city at dusk. The low light means you want a very slow shutter speed (or long exposure).

 Barrel racing in the arena in the middle of the day Aperture f4.5 Shutter Speed 1/5000 ISO 650
Barrel racing in the arena in the middle of the day
Aperture f4.5
Shutter Speed 1/5000
ISO 650


Saloon not long after sunset Aperture f2.8 Shutter Speed 1/40 ISO 3200
Saloon not long after sunset
Aperture f2.8
Shutter Speed 1/40
ISO 3200

In effect you could shoot the same scene three times all with very different (yet still interconnected settings) where they are all ‘correctly exposed’ but the emphasis or character of each one will look different. Having control over this is why it’s fun and good to play with camera settings as well as have the option to go fully automatic.

So, take a look at your camera (and lenses if you have a DSLR), and see what your ranges are with respect to aperture, shutter speed and ISO. Even if you don’t want to play with them (or can’t because you are fully auto), it will at least help you understand the scope of what your camera can and can’t do when taking a picture. If you are feeling brave use the symbols (for portrait, landscape, action etc.) as these pre-sets will give your auto camera a clue about your subject matter. Then if you have it, move on to the A (Aperture Priority) where you set the aperture for what you want and it automatically adjusts the shutter speed to cope, or TV (Shutter Speed Priority) where you set the shutter speed you want and the camera selects your aperture. See what you get and then when you’re ready make the move to M (Manual) and the independently adjustable ISO dial and get yourself full control!

In the meantime here’s a few more photos where hopefully you can see the impact of the three settings:

windmill at black mountain ranch
Aperture f8.0
Shutter Speed 1/100
ISO 100
idiots guide to horseback riding
Aperture f2.8
Shutter 1/100
ISO 2000
brice roping
roping in the arena late afternoon
Aperture f4.0
Shutter Speed 1/8000
ISO 4000

Next week: Which camera is right for you



The Pikey Project

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