Exposure Triangle – ISO

**Special thank you to Oh Loops Yarn for sponsoring the yarn for these tutorials! These will be a supplement to a larger tutorial coming soon!**

In this tutorial and three others, we are going to explore the Exposure Triangle. The exposure triangle is the combination of three ways to help light enter your camera: Shutter speed, Aperture, and ISO. These three aspects of photography will help your camera get the correct exposure, while giving you complete control on how you want each final image to look. We will start with each piece of the triangle, then look at how those three pieces work together.

ISO – How Does It Work?

In the previous exposure triangle tutorials, we talked about how light enters a camera through a lens and lands on a sensor. This sensor is what captures the image to create a photograph. In this tutorial, we will talk about ISO. ISO is the rate the sensor will absorb light. ISO measurements are written in increments of 100, such as ISO 200, ISO 800, and ISO 2,000. Higher ISO numbers mean light is being absorbed onto the sensor at a faster rate, making the image brighter. Here is the same photograph shot with different ISO rates:

The same image shot with ISO 100, 400, and 1250. No other adjustments were made to compensate for exposure.

The same image shot with ISO 100, 400, and 1250. No other adjustments were made to compensate for exposure.

SO is an excellent tool to use when you need to increase the amount of light in an image without changing the aperture or shutter speed. However, raising ISO does come with a cost. Higher ISO will result in more noise in an image, which is the graininess and color distortions shown below. 

In these images, (the same images as above at 100, 400, and 1200 ISO) you can see the difference in the coloring and noise levels when zoomed in. On the right you can see the high levels of pixelation and blur between the colors, making for a less than desirable image.

In these images, (the same images as above at 100, 400, and 1200 ISO) you can see the difference in the coloring and noise levels when zoomed in. On the right you can see the high levels of pixelation and blur between the colors, making for a less than desirable image.

 

While the DSLRs currently on the market advertise handling extremely high ISOs, keep in mind that these levels will result in a very high amount of noise in the image. Fortunately, today’s sensors on an entry level DSLR can handle ISO levels up to 1,000 and above without too much noise. 

How Do I Adjust ISO?

ISO adjustment can only happen in the Manual (M), Aperture Priority (A or Av), Shutter Priority (S or Tv), or Program (P) modes on your camera. All of the other modes will automatically adjust the ISO level for you based on the level of light entering the camera. 

There are a few ways to adjust ISO. The first is to manually set it in the menu system. While you should always consult your manual to see your exact model of camera, here is how I can manually set the ISO on my Nikon D5200.

I have found this way of setting ISO to be extremely tedious, especially when I am on a photoshoot that will have light changes. Instead, I have mapped the Function (Fn) button the side of my camera to adjust the ISO when I spin the adjustment dial. Here is how I do that:

You can also set the ISO to automatically be as low as possible while still exposing the image correctly. Here is how I do that on my camera:

**Thanks to the youtube channel Camera Guides for all of the helpful videos!

What ISO Do I Use?

The level of ISO you set will depend on the amount of light coming in to the camera. In bright sunlight, use lower ISOs to create the least amount of noise. In dark situations such as photographing street lights or night photography, use high ISOs to allow the light to be absorbed as quickly as possible. Be sure to download the exposure guide I have created for you to have an at-a-glance guide on how ISO levels will adjust the light and noise levels. Here are some images I have taken with explanations for each of the ISO levels:

Night photography often requires a high ISO, however, when photographing the moon I like to use a lower ISO to make the craters and shadows properly exposed.

Night photography often requires a high ISO, however, when photographing the moon I like to use a lower ISO to make the craters and shadows properly exposed.

This image was taken using an extremely high ISO of 2000. I only used this high of ISO because it was getting dark when we shot this image, but it created a dreamlike grain I really enjoy.

This image was taken using an extremely high ISO of 2000. I only used this high of ISO because it was getting dark when we shot this image, but it created a dreamlike grain I really enjoy.

I try to use the lowest possible ISO when I do product photography. Grain can make a client unsure of what the actual product will look like.

I try to use the lowest possible ISO when I do product photography. Grain can make a client unsure of what the actual product will look like.

When photographing a subject in front of a window I like to use a high ISO. This makes the window appear “blown out” so the viewer can’t see what is beyond, and the subject is properly exposed.

When you have had an opportunity to play with your ISO levels, here are some extra tips I have for you in using ISO:

  • I set my aperture where I would like it, then set my ISO to the lowest number possible while maintaining a shutter speed of at least 1/200. When doing portrait or product photography, this creates the least amount of noise while still having a high enough shutter speed to expose the image correctly.
  • I use higher ISOs occasionally to overexpose my image if I want to photograph a subject in front of a bright window. I often already have the lowest aperture and shutter available in these types of images, so raising the ISO is a quick way to make the window appear completely bright and correctly expose the subject in front of it.

Helpful Links:

If you are interested in learning more about ISO and how it works, visit some of my favorite sites and read their take on it:

Do you have any questions about ISO? Have you used this tutorial to help you take photographs? Post in the comments below, and feel free to link to your site!

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