Photography for absolute beginners: how do I take a photograph that is correctly exposed?
‘Exposure’ was one of the most difficult things for me to understand when I started taking photographs; what it was and how to get it right. In this short article I’ll try to explain in over-simple terms my own understanding of this topic.
What does it mean have a photograph correctly exposed?
In essence; a correctly exposed photograph is one where the resulting photograph accurately reproduces the scene being photographed – in terms of how light or dark the scene appeared at the time.
Alternatively – if we take artistic considerations into account; it is correctly exposed when the photograph reflects the aims of the photographer; again in terms of how dark or light the photograph is (or elements within the photograph).
So what is meant by over exposure and under exposure?
In the old world of black and white film photography; to make a picture, light falls on the film – that light causes a chemical reaction which makes those parts of the film that get the most light – lighter – and those parts that get least light – not as light. So the photograph is the mix of light and dark – and the gradation between these extremes makes the picture. The light and dark ares of the photograph reflects the light and dark parts of the scene that has been photographed.
- With an extremely over-exposed photograph – everything will be white – with no dark areas because so much light has fallen on the film that every bit of the film gets lighter and lighter until no dark areas remain.
- In an extremely under-exposed photograph – everything is dark; not enough light has fallen on the film to start any chemical reactions; which results in no bits of the film getting lighter.
What about digital photographs?
The principles are exactly the same whether you are taking old style photographs using film or taking digital photographs. Film is replaced with an electronic sensor that records the amount of light that falls on a particular point on the sensor.
How do you control the exposure of your photographs?
In general, we don’t want our photographs to be too light or too dark. If we didn’t have sophisticated modern cameras we would have to work out for ourselves how much light needed to fall on our film (or sensor) to make a well exposed photograph.
We would work this out by taking into account a combination of the length of time the camera shutter should be open (shutter speed) – and the size of the opening letting in that light (aperture). This is not easy. We would need to think about how much light the thing we are photographing is reflecting – how much light is available in general (sunny day or dull day?) and so on. There are in fact a multiplicity of variables to think about – enough to screw your head up and make you think that taking correctly exposed photographs is impossible. 🙁
Your camera has magic powers
The good news is that modern cameras are extremely sophisticated – and do most of this work for you. When you set your camera to automatic, the camera works out the most appropriate shutters speed and aperture settings – based on the information reflected back from the scene being photographed. Now that’s great – but it doesn’t leave much for you to do; and it doesn’t give you the sort of control that you need so that you can bring your artistic preferences to bear when it comes to decisions about exposure.
The thing is – the scene you want to take a photograph of will consist of light areas and dark areas – and it is likely that you are particularly interested in ensuring that one part of the scene is the focus of your picture and therefore needs to be rendered in detail (One of the problems of incorrect exposure is a loss of detail, either because it’s ‘burned out’ or too dark to see).
That will be achieved if that part of the photograph is correctly exposed. For example, you are taking a photograph of your friend standing on the beach and they have the sun behind them. If you leave it to your camera to work out the correct exposure for you – you are unlikely to get a good photograph of your friend. They will probably just be a dark silhouette – set against the bright background.
This is because the scene will be dominated by the light from the sun behind your friend – which you camera will cope with by using a short shutter speed and/or small aperture setting to limit the amount of light getting on to the film (or sensor). The camera is working out the correct exposure for a bright scene; it doesn’t know you are actually wanting a shot of our friend – and in particular their smiley face. It is at this point you need to take control of the exposure yourself.
There are many ways you can approach this – but let’s start by understanding the problem. If you have a digital camera you can look at the photography you have just taken and notice that your friends face is very dark – so dark you can’t even make out their features. This tells you that you need to let more light into the camera – either by making the shutter speed slower or increasing the size of the opening that that lets the light in. It’s time to move that dial off automatic. 🙂
Taking control of the exposure
When we take the dial off of automatic we aren’t entirely left to fend for ourselves – the camera will still help us to set an appropriate exposure. The two choices that most cameras offer us when moving from the safety of the fully automatic setting are ‘aperture priority’ and ‘shutter priority’. With shutter priority – we set the shutter speed and the camera picks an appropriate aperture setting; with aperture priority we set the aperture and the camera chooses the shutter speed for us.
Ok that’s great – we now have control over one aspect of photography, i.e., either the aperture or the shutter speed. So how is this going to help us correctly expose our scene so that we can see our friends face?
Say we choose to set a very quick shutter speed – because this is a bright scene we don’t need the shutter to be open too long to get lots of light into the camera – and we take another photograph. You look at it – and it’s not any better – because the camera is still trying to help you by setting what it thinks is the appropriate aperture for the scene – the wrong aperture in this case.
Time to use some exposure compensation
Now that you are in creative mode – your camera is likely to give you access to a feature called ‘exposure compensation’. This might help us to sort this problem. Exposure compensation takes as it’s default level the exposure that your camera has chosen for you – and lets you either decrease or increase the exposure. Increasing exposure means more light gets in – decreasing exposure means less light gets in. So what do we need to try to fix our problem?
If you said more light you are right. Even though this is a very bright scene we aren’t interested in taking a picture of the sun – we want a picture of your friends face – which has been coming out very dark up to this point. So we increase the exposure using exposure compensation. Increase the compensation index one point at a time and note how the photograph changes – as you increase the exposure compensation you will see more and more detail of your friends face. In practice the sun may be just too bright that no matter how much exposure compensation you set it still dominates the photograph – however by doing this exercise you have learned a valuable lesson about how exposure works. The is another approach we can take to solve this problem – but I’ll leave that for another article.
Trying to take a well exposed photograph is good for teaching us an important lesson. The lesson is; we need to be in control of the camera settings ourselves – and not let the camera dictate us how a photograph will look by just accepting the default exposure settings it gives us.
This article is part of my, ‘guide to photography for beginners like me’ series.
Enjoy your photography
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