Snapshots to Photographs-Learn The Secrets Of ISO

This episode of Mark’s Photography Spot is the second in a series of videos I’m doing to help you get your camera out of “Auto” mode. I call the series “Snapshots to Photographs” This episode is about one of the key components of exposure-ISO, which determines your camera’s sensitivity to light.

Here’s a more detailed description:

ISO-This determines your camera’s sensitivity to light. The higher the number, the more sensitive, the lower the ISO, the less sensitive. ISO is expressed in numbers, usually something like 100,200,400,800,1600,3200. Each larger number indicates a doubling in sensitivity. So, going from an ISO of 100 to 400 means that the camera is going to be four times as sensitive to light at ISO 400 then ISO 100. Higher ISO can help you get an image you might not be able to get, especially in lower light but it comes at the price of increased noise in the image.

You can use ISO to give you more shooting options. By increasing the ISO you have the ability to get images in conditions you might not be able to otherwise. Here are some examples:


  1. You can increase ISO in order to be able to capture an image in a lower light environment such as a concert. By bumping up the ISO you can compensate for a darkened room and still be able to capture images.
  2. A higher ISO can allow you to use a higher shutter speed-Each “bump” up in ISO allows you to use a shutter speed that is ½ as fast. So, for example, going from ISO 100 to 400 will allow you to increase your shutter speed from 1/250 to 1/1000 (all other things being equal), which might be needed in order to stop action effectively. This is one of the ways that many sports photographers are able to get the shots they do, by using a high quality zoom lens along with a camera that does well at higher ISO.
  3. If you are looking to increase the depth of field in a photo, shooting through a smaller aperture (ones with a bigger f/number) is needed. Sometimes the only way to accomplish this is by increasing the camera’s light sensitivity (ISO).

There are other ways that ISO is used in photography but the three I mentioned above seem to be the most common. As you gain more experience with your camera you will learn what ISO settings work best, given the capabilities of your camera and the lenses you own. The key is to not be afraid to experiment and see for yourself the differences in using a high or low ISO make in your images.

While setting a high ISO is often a recipe for increased noise i an image, the software tools we have available to us today can clean a surprising amount of that noise up. My recommendation is to always use the lowest ISO you can, just to reduce the amount of noise in your images as much as possible.

As I have mentioned in the previous videos, a great resource for learning more about exposure is the book “Understanding Exposure”, written by Bryan Peterson. It is well worth reading and explains how ISO, Aperture and Shutter interact to create a final image. Here is a link to the book on Amazon:

Stay tuned for the next videos in this series as I dig a little deeper into Aperture and Shutter Speed.

You’ll be able to find all the videos in this series in the playlist “Snapshots to Photographs”.

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