Understanding Exposure

[Flutterby]

By Darren Rowse - http://digital-photography-school.com

The three elements of exposure are:

ISO – the measure of a digital camera sensor’s sensitivity to light
Aperture – the size of the opening in the lens when a picture is taken
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.

2 Metaphors for understanding the digital photography exposure triangle:
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 two. A quick word of warning first though – like most metaphors – these are far from perfect and are just for illustrative purposes:

The Window
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.

Sunbaking
Another way that a friend recently shared with me is to think about digital camera exposure as being like getting a sun tan.
Now getting a suntan is something I always wanted growing up – but unfortunately being very fair skinned it was something that I never really achieved. All I did was get burnt when I went out into the sun. In a sense your skin type is like an ISO rating. Some people are more sensitive to the sun than others.
Shutter speed in this metaphor is like the length of time you spend out in the sun. The longer you spend in the sun the increased chances of you getting a tan (of course spending too long in the sun can mean being over exposed).
Aperture is like sunscreen which you apply to your skin. Sunscreen blocks the sun at different rates depending upon it’s strength. Apply a high strength sunscreen and you decrease the amount of sunlight that gets through – and as a result even a person with highly sensitive skin can spend more time in the sun (ie decrease the Aperture and you can slow down shutter speed and/or decrease ISO).

As I’ve said – neither metaphor is perfect but both illustrate the interconnectedness of shutter speed, aperture and ISO on your digital camera.

[Amoli]

Brilliant thread FB.... easy to understand

[Flutterby]

I thought it might be helpful to you!!

[Grumpy]

To Flutterby.... you are an angel for posting such articles. I just hope that people take the time to read and understand the contents, as in understanding these three basic, but technical elements of photography should help them in capturing correctly-exposed images.

[Flutterby]

Well, at least 2 people have read it!!!

[PRWIN]

Have read them all, Flutterby stop giving the secrets away -O -O -O

[Grumpy]

For a site that I often visit and is friendly, have a look at http://mansurovs.com/iso-shutter-speed- ... -beginners

[Flutterby]

Tx Grumpy!

[Grumpy]

In a word – “exposure” – is what photography is all about. Photography means writing with light in Greek, and exposure is the combination of three factors that determine what the light writes… hence the Exposure Triangle and its three components.

Those three elements are: ISO, Aperture and Shutter Speed.

The ISO rating (which is an international standard) measures the image sensor’s sensitivity to light.
The Aperture determines how much light enters the lens.
The Shutter Speed determines the amount of time the level of light enters the lens.

Everything (well, almost everything) else in photography is superfluous to these three elements. Understand these, and you will understand why your pictures look like they do ..... then practice, practice and experiment some more

[Sprocky]

Thanks form these posts Flutters.

This is the best "real" example I have seen of how these elements, plus a few more work to produce good photographs.

Take a few minutes to play with this camera. http://dryreading.com/camera/index.html

You will be able to see what happens with every setting change you make.