The Three Pillars of Photography: #1- ISO

June 30, 2014  •  Leave a Comment
  • Did you spend a decent chunk of change on a fancy camera but only ever use the "auto" setting?
  • Are your photos occasionally blurry or the people you are photographing come out too dark?
  • Do you want to learn more about taking better photos of your travels, your children, and/or your friends and family?
  • Do you hear all of these terms such as ISO and aperture but aren't exactly sure how they work?  

Well, then my next few blog posts are for you!  I'm going to cover the very basics of your camera so you can capture your best images of all of your life adventures.  To start, photography is built on three pillars of exposure:

  1. Shutter speed
  2. Aperture
  3. Sensitivity to light (ISO)

These three lay the foundational knowledge to get the most out of your camera equipment and show off your creativity.  Each post will cover one topic and give you the basic information so you will have the expertise to adjust your settings and improve your images.  To start, let's cover the fundamentals of ISO!


In very basic terms, ISO is the level of your camera’s sensitivity to available light.  The lower the ISO number, the less sensitive it is to light.  In bright scenes, a low ISO will suffice because there is plenty of available light for the camera to capture a properly exposed image. While a higher ISO number increases the sensitivity of the camera’s sensor to light, which is very valuable in dark settings. ISO Cheat Sheet

The ISO setting has two significant relationships:

First, it sets the amount of light needed for a good exposure.  The lower the number,the more light required to capture the image.  The more light that’s required, the more likely a slow shutter speed will have to be used.  Therefore, low ISOs, such as 100 or 200, are most often used in bright settings (sunny outdoor scene) when there is a lot of light available for the image.  If the setting is not bright and sunny, a low ISO will probably mean that the camera will need a longer shutter speed to capture a properly exposed image.  Therefore, when the setting is dim, a low ISO can be used when the camera is mounted on a tripod to steady the camera for the longer shutter speed.  However, if there is not enough light to produce a properly exposed image, or if a faster shutter speed is needed because your subject is moving, then the ISO needs to be increased in order to allow the camera to be more sensitive to light to capture the image.  Remember, increasing the ISO makes the camera more sensitive to light.  In turn, the camera won't need as long of a shutter speed to capture the image.

Second, ISO determines the amount of noise in the image.  In the days of film, high ISO values would produce visible grain in the images.  Today, with digital cameras, raising the ISO still has a similar decrease in the quality of the image because it introduces “noise.”  Although, most DSLR cameras are capable of producing quality images at high ISOs, such as 1600 and above.  In general, I like to keep my ISO below 1600 if I can help it.

The goal is to balance the need for high quality images (low ISO, thus low noise) with a fast enough shutter speed for a sharp photo at your desired aperture.


So here are two life scenarios for you:

  • You have an all-star little leaguer that you are trying to capture at bat, although your images keep coming out blurry on an overcast day.  The blur is caused because the shutter speed is open too long.  So what can you do?  You can increase your ISO to make your camera more sensitive to the overcast light and decrease the shutter speed.
  • You are trying to take some photos with your friends at an indoor soirée but all of your images are slightly blurred.  You know that you only had one drink so it isn't the booze (for the moment). Bump up your ISO to around 800 and try again.  If it is still blurry, you can always push it to 1600. In really dark environments, even a high ISO of 3200 or 6400 is no guarantee of fast shutter speeds. In these situations, try to brace the camera or rest your elbow on a rigid surface.  It may not be the cure, but it will help reduce the amount of camera shake (blur) in the image.


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