Covering the basics

For those who have a new DSLR camera and have been playing around with it, but want to figure out how to do more with it….

...first of all let me just tell you that going "manual" isn't as scary as it first sounds - and getting to know how to use the camera off-auto will enable you to vastly improve your control over the shots you take.

In this blog we'll cover the exposure of the image and what settings affect this. I've not covered the practical 'how' to change these settings as each manufacturer differs in where the camera controls are - but a quick look at your camera manual will enable you to get to grips with the controls - this is mainly around 'what' each does.

Also, just a note that understanding what these controls do and how they interact with each other will take you a lot further than just buying the latest & greatest camera!

The Exposure Triangle

The exposure of the image is derived from 3 factors – ISO, Shutter speed & Aperture, generally referred to as the exposure triangle as each plays a different role but all affect the overall exposure of the image – it’s often a balancing act, playing off one against the other to achieve the desired effect.

ISO – the ISO is basically an electronic amplification of the light detected by the camera’s sensor. This can be very useful in low light situations where you have a desired shutter speed and aperture – the play off with this is that whilst amplifying the light, it also amplifies noise. Increasing the ISO adds graininess to the end image. Modern DSLRs are much improved over ones from 5 - 10 years ago so you can really push the ISO on these and you can also process some of the noise out using software (will cover this another time). Don’t fear increasing the ISO when you need to, but ideally keep it as low as you can to avoid increasing noise.

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Shutter speed – the longer the shutter is held open, the more light hits the sensor. So in theory, rather than increasing the ISO to increase the exposure, you could increase the duration that the shutter is open for – there are of course other effects of the shutter speed that you need to take into consideration…

...the slower the shutter speed, the more any movement is picked up which creates blur in the end image (although sometime this can be a great effect!)

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This was shot at 1/250s - fast enough to freeze the players but slow enough to get some blur on the ball and the players arms to emphasise movement

...there’s only so long you can keep the camera steady whilst hand held – get beyond a certain shutter speed and you’ll need a tripod to keep the camera steady and avoid camera shake.

A general rule of thumb is to keep the shutter speed above the reciprocal of the lens focal length – so if shooting with a 200mm lens, use a shutter speed no slower than 1/200 second. This is a bit flexible as some people can hold the camera a bit steadier than others. Many lenses come with some form of Image Stabilisation which also helps maintain a slower shutter speed

...if the subject is stationary, you can keep a fairly slow shutter speed – but if your subject is moving (perhaps someone playing a sport), you’re likely to need a faster shutter speed to freeze the action.

There are other techniques such as panning which allow you to keep a slower shutter speed but you move the camera with the action so that the subject stays sharp but the background blurs (this takes a bit of practice!)

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Aperture – the aperture is how wide the shutter opens when you take the image. A wide open shutter allows more light to reach the sensor than a narrow aperture… bear in mind here that a wide open aperture has a smaller f number than a narrow aperture (it’s all to do with the inverse square law but we don’t need to hit all that maths – just know that f/1.4 is a wide open aperture and as the f number increases to say f/22, the aperture is narrowing. There is of course a side affect of varying the aperture (bound to be something else to complicate matters!) - the wider the aperture, the shallower the depth of field…

...depth of field is how much will be in focus (front to back) from the focal point – with an aperture of f/1.8 (wide) the range from front to back of how much will be in focus is very small.

This can be good for things such as portrait or product shots where you want to direct the viewers attention to a specific region of the image & creating some distinctive boke – but not so good for say a landscape shot where you want the viewer to be immersed in the whole vista of the shot so want everything in focus.

For a landscape shot you may want to narrow the aperture down to say f/16 to improve the depth of field - but knowing that this will reduce the light hitting the sensor, you’ll need to have a slower shutter speed or higher ISO….see how it becomes a pay off from one variable to the others?

Generally speaking for landscape you’d use a tripod so that you can keep a low ISO, aperture to about f/16 and slow the shutter speed down enough for the right exposure given the available light.

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This was taken at f/1.8 to really narrow down the depth of field and focus the viewer on the taped finger, chalk and the ability of the climber using such minimal grip

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Of course, it’s never going to be a simple as just the exposure triangle (although this knowledge goes a great way in enabling you to select Manual and take full control of the camera) – there’s where to focus, how far from the subject to be (and how far from the background for the subject of the photo to be too!!). A lot depends on what lens you’re using and what you are trying to achieve – I’ll cover some more in a later blog but for now, get out there shooting and see what results you get. A distinct plus of digital photography is that you can take plenty of shots to experiment with settings and not be using up valuable film – just delete the ones that don’t go quite right!

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