Learning about exposure

If you’ve been wanting to venture out of the Auto mode on your digital camera and experiment with it’s manual settings there’s some tips that you might find useful.

There are three main elements that need to be considered when playing around with exposure by calling them ‘the exposure triangle’.

Each of the three aspects of the triangle relate to light and how it enters and interacts with the camera.

The three elements are:

1.ISO value– the measure of a digital camera sensor’s sensitivity to light

2.Aperture – the size of the opening in the lens when a picture is taken

3.Shutter Speed – the amount of time that the shutter is open

It is at the intersection of these three elements that an image’s exposure is worked out.

Most importantly – a change in one of the elements will impact the others. This means that you can never really isolate just one of the elements alone but always need to have the others in the back of your mind.

Many people describe the relationship between ISO, Aperture and Shutter Speed using different metaphors to help us get our heads around it. Let me share one of them:

The Window

Window and flowers

Imagine your camera is like a window with shutters that open and close.

Aperture is the size of the window. If it’s bigger more light gets through and the room is brighter.

Shutter Speed is the amount of time that the shutters of the window are open. The longer you leave them open the more that comes in.

Now imagine that you’re inside the room and are wearing sunglasses (hopefully this isn’t too much of a stretch). Your eyes become desensitized to the light that comes in (it’s like a low ISO).

There are a number of ways of increasing the amount of light in the room (or at least how much it seems that there is. You could increase the time that the shutters are open (decrease shutter speed), you could increase the size of the window (increase aperture) or you could take off your sunglasses (make the ISO larger).

Ok – it’s not the perfect illustration – but you get the idea.

Mastering the art of exposure is something that takes a lot of practice. In many ways it’s a juggling act and even the most experienced photographers experiment and tweak their settings as they go. Keep in mind that changing each element not only impacts the exposure of the image but each one also has an impact upon other aspects of it (ie changing aperture changes depth of field, changing ISO changes the graininess of a shot and changing shutter speed impacts how motion is captured).

The great thing about digital cameras is that they are the ideal testing bed for learning about exposure. You can take as many shots as you like at no cost and they not only allow you to shoot in Auto mode and Manual mode – but also generally have semi-automatic modes like aperture priority and shutter priority modes which allow you to make decisions about one or two elements of the triangle and let the camera handle the other elements.

Photo credits: Wam1975.
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June 08, 2010

Ahhh this is so helpful. I do struggle with the numbers.


June 08, 2010

Really helpful, nice to read.


June 08, 2010

great blog, thanks for sharing :)


June 08, 2010

It may look like the basics but needs a lot of trial and error to get it into a fine art.


June 07, 2010

You might be surprised to find how many people (even DT contributors) do not have the basics in terms of photography and use auto mode or even shoot randomly (in terms of settings) thinking they'll try to get the best of it in the post-production process ... any way ... this was suppose to be useful for beginners especially and also a reminder for experienced readers :P

I can see you're a tough crowd ... I promise to get back to you with other "more advanced" articles!


June 07, 2010

and whenever I'm not sure about any of those settings, I turn the dial to the good ol' P take a shot, go back to Av, Tv or M, and tweak accordingly...


June 07, 2010

Nice to read again the basics of photography.


June 07, 2010

good to read again!


June 07, 2010

I think and hope, the vast majority of contributers already knows these facts ... but it's always good to re-think these points.