Take better photos: Understanding ISO

Hopefully you have read my previous blogs on taking better photos that taught about your camera’s Aperture Setting (shown as AV on most cameras) and Shutter Speed (shown as TV on most cameras) setting.  The light that your camera captures to make photos is affected by those two factors and one more important factor you will want to have a basic understanding of. And that is your camera’s ISO setting.

The lower the ISO, the less sensitive your sensor is to light, so you need a lot of light coming into your sensor. The higher the ISO, the more sensitive your sensor is to light, so you don’t need as much light coming into your sensor. There is a trade off, however. While a higher ISO is more sensitive to light, it also introduces digital noise (or grain) into your image. That noise means your image will not appear as clear and crisp, especially if it’s viewed at a large size.


ISO stands for the International Organization of Standardization which doesn’t really mean anything other than they are the ones that set standards and in the case of your camera, the ISO is the standard measurement of how sensitive your camera’s sensor is


The lower the ISO, the less sensitive to light your camera’s sensor is. If you are in a low light situation and need your camera’s sensor to be more sensitive to pick up what little light there is then you would want your ISO to be set higher (more sensitive).


One key thing to be aware of is that the higher the ISO the more grain your picture will have. Even if you are completely in focus and have a very still subject, if it’s really low light and you have to crank your ISO up really high then you will be left with a grainy image which means it will not be sharp and it will look pixelated.

Generally speaking, you want to shoot at the lowest ISO you can. However, you will have to consider the AV setting and Shutter Speed to ensure that you are getting enough light into the camera to capture the image you want.


In 2015 I had the privilege of joining singer/songwriter Matt Williams, musician and business man Sean Bennett, and musician Aaron Gray (who is a dear friend of mine and my ticket into the whole scene) at the famed London Bridge Studio just outside of Seattle Washington. They were working on some songs for an upcoming album. It was a really cool venue with a lot of personality. But well lit it was not! I did a few scenes with a flash set up. But it really took away from the gritty vibe of the place. So I turned off the flash and just adjusted my ISO to allow more light into the camera. Here are a few photos I got from that day.

They may look ok as a relatively small image on your computer. But if you were to see it blown up to full size you would see that there's quite a bit of grain.

Let me show you one image in more detail. Take a look at the following (click on it to see it blown up full size). I shot this image at an ISO of 12,800. 

Take a look at a close up of his hands. Do you see how grainy the image is?

Do you see how grainy the image is? Now look at an image I shot on a bright sunny day using ain ISO of 100.

Do you see how crisp and clean the close up of this image is compared to the close up of singer/songwriter Matt Williams?


Hopefully my three blog entries on Aperture, Shutter Speed, and ISO have helped you gain a basic understanding of the key variables you can control to help create images with greater impact. If you want to do a little more reading on the subject there’s a great article on the Canon Digital Learning Center site written by Laura Morita titled How Understanding the Exposure Triangle Will Help You Get Better Pictures.

If you search for Exposure Triangle you can find a number of helpful illustrations that show the relationship between Aperture, Shutter Speed, and ISO.


So you don’t get confused when you compare those charts to my blogs, you should be aware that when I talked about a larger AV setting, I was speaking in the most layman terms possible. Meaning that I referred to a 2.8 as a small AV setting and a 22 as a large AV setting.

If you plan to gain a better technical understanding of all of these camera settings then it’s good to learn what’s going on under the hood so to speak. I’ll provide a BRIEF explanation here. While my way of speaking about the AV value was true (a smaller number on the AV setting gives a smaller depth of field) in technical speak, a 2.8 is referred to as a large aperture. What? But that’s a small number. Here’s why they say it that way. When your camera is set to an AV of 2.8 your camera’s aperture (the opening the light comes in) is a LARGE opening. The large opening lets a lot of light in. So most references you read will refer to an AV setting of an f 2.8 as a large AV value meaning a large opening and lots of light. Conversely, an AV value of 22 means there is a small opening in the aperture and very little light can get in. So technical speak will say a small AV meaning a small aperture. You can click HERE to see a diagram that may help explain this.

So why did I talk about it the way I did? I certainly was not trying to confuse you. I wrote with a non technical audience in mind and I wanted to make a SIMPLE correlation to make it easy to remember. The correlation I was highlighting is that the smaller the number for your AV setting, the smaller the depth of field. The larger the number for your AV setting, the larger your depth of field. And I hope you can keep that locked away because it’s a fast way to think about how to shape the depth of field in your images which is also a powerful way to add impact.


Hopefully you’ve taken some time to take on the assignment challenges I provided in the blog’s about your AV and Shutter Speed settings.

For today’s assignment, I want you to head out just before sunset. Put your camera on full manual. Start with your ISO at 100 and then adjust your AV and Shutter Speed to an appropriate setting to get a proper exposure.

Then, every few minutes, take a photo. As the sun sets, and especially after sunsets, notice how the image will appear darker and darker on your play back screen.  To compensate, increase the ISO till you are getting a proper exposure. Continue that process until you are shooting at your maximum ISO.

Then, put your images on your computer so you can see them blown up much larger. Take special note of how the grain got more and more noticeable as the ISO increased.
This should give you a much better understanding of how your camera’s ISO impacts your photographs. It allows more light in, but it also increases grain (also called noise) into your images.

I hope that helps! Now keep playing with the different settings (AV, TV, and ISO) until you feel really confident that you can identify which setting is most important to you to help accomplish the image you want to capture at any given time.

Happy shooting!