Exposure: A Beginner’s Guide


I’ve been wanting to do this for a while now because I know how important it is to understand how a camera takes photos.  Lots of people have asked me to do a beginner’s workshop, and although I have plans for it hopefully in the near future, I don’t have the means to at the moment.  Hopefully this will do for now.  So without further ado…lets talk about photography!

EXPOSURE:

Exposure refers to how bright or dark your photo is. This is effected by the amount of light that is recorded by your camera’s sensor. A properly exposed photo should typically resemble the brightness of the original scene. A poorly exposed photo will either be too dark (under exposed) or too bright (over exposed), and may contain areas that are so dark or so bright that they contain no detail (know as being blown out).

In case you didn’t already know, photography uses light.  In fact, the word “photography” comes from two Greek words, photo– meaning light and graphy – meaning draw.  So a “photograph” is like a light drawing.  Your camera uses light to capture what is sees.  Depending on your type of camera (film or digital), the light then “draws” what it captures on film or type of sensor that acts as a sort of “digital film”.

“How?” you might ask.  Well, lets look at some major parts of a camera.  All cameras, whether film or digital, have a lens.  Inside this lens is something called the aperture.  The aperture is a mechanism that can be adjusted in size to control the AMOUNT of light is allowed in.   Its like the pupils of your eye.  When you are outside on a sunny day, your pupils get smaller to control the amount of light.  Have you ever seen a cats eyes react to light?  When it is dark a cats pupils get HUGE!  When a cat is in a lot of sunlight, their pupils get very small.  Just like the pupils in a cat’s eyes get smaller or larger, the aperture of the camera’s lens gets smaller or larger to manage amounts of light.

Let’s try something.  Make a fist and close one eye.  Open your fist just enough to see through and place it over your open eye.

aperture example using fist sbjamesphotography

This is my hand..tada!

 

See how much light comes in?  Not much right?  The wider the aperture, the more light can come into the camera.  Why is this important?  The aperture also controls something called Depth of Field which we’ll talk about a little bit later.

All cameras also have whats called a shutter.  Imagine its a terribly cold and windy day.  In fact, its so cold and windy that you can’t stand it and the only thing keeping you from all that cold and wind is a door.  The LONGER you leave the door OPEN, the more wind and cold will come in.  The camera’s shutter is like a door.  The longer the shutter stays open, the LONGER light will come come into the camera.  The shorter amount of time the shutter stays open, the less time light has to come in.

The amount of time the shutter stays open is called shutter speed.  Shutter speed also affects how movement is recorded on a photo, but we will discuss that a little later as well.

The other component to exposure is ISO.   ISO is basically a numbering system created by the International Organization for Standardization to represent the sensitivity of film negatives (if you’re still using film,film sensitivity may also use a scale created by the American Standards Association or ASA however most digital cameras now call the setting ISO).  ISO controls how sensitive to light your film or digital camera sensor will be.  Most normal cameras have an ISO range from 100-1600.  Some cameras have lower or higher values.

Have you ever had your eyes dilated when going to get an eye exam?  They tell you that your eyes will be very sensitive to light and give you these crazy looking “sunglasses” to put on.  Ok, ok…that really has nothing to do with ISO at all.

ISO, like aperture and shutter speed, will control the overall brightness of your photo.  Its sortof like this…

Imagine you have a container under a water faucet.  The water will be “light” and the container will be your “film” or digital sensor.  Lets say you turn the faucet on slightly, letting a small amount of “light” flow. The container or “film” would take in this small amount of “light”.  This would be a low ISO setting.  The higher the ISO setting, the more “light” flows out of the faucet and into your container (film or digital sensor).  ISO can allow you to adjust your shutter speed and aperture to get desired effects in your photographs.

ISO illustration

There is a downside to raising the ISO value.  The higher you raise the ISO, the more noise or film grain you will see on your image.  This can affect how crisp and sharp your photo appears.  We will talk more about noise later.

So, we’ve discussed the three main aspects of exposure, commonly referred to as the Exposure Triangle.  By combining the aperture, shutter speed and ISO values, proper exposure can be achieved.  Next we will talk about the different things aperture, shutter speed and ISO affect and some typical combinations for different outdoor lighting situations.

exposure triangle sbjamesphotography

I hope you found this post helpful and interesting.  If you have any suggestions on how I can improve it or other topics you’d like discussed, please let me know.  Feel free to post comments and questions to help other readers.

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