Photography Craft: ISO

Welcome Wordsmiths! This week, we will be exploring ISO in more detail.


In digital photography, ISO is a measurement of light sensitivity. It is how easily the camera’s sensor can detect light. It doesn’t really have a unit of measurement; it’s just designated by a number. ISO is used most commonly to affect exposure, but can also add grain to your image. 

In film, it has something to do with speed. I don’t know much about film photography, so this article will focus only on digital.


As we discussed a few weeks ago, ISO is one of three factors affecting the exposure of a particular image. You can change the ISO on your camera to allow the sensor to be more or less sensitive to the available light, depending on your needs. 

Usually, the ISO will be chosen automatically by your camera to make a good exposure based on the settings you choose for aperture and shutter speed. Honestly, I don’t pay much attention to my ISO unless it’s too dark to get a good exposure at the low ISO I keep it on.

You can increase your ISO to get brighter images in lower light situations when you can’t use a flash, or when you need to use a faster shutter speed to freeze motion in low light. Here are a few places you might want to consider increasing your ISO: indoor sporting events, concerts, churches, art galleries, and museums. 

Image Grain

A side effect of using a higher ISO is image grain. In some cases, you might want this effect. I can’t really think of any instances I would want it, but you might. I generally try my best to avoid it. Here are some photos I took of my Christmas tree to show you what I mean.

ISO: 200, 6400

I didn’t do any editing to these images other than cropping. You can see that the photo with the higher ISO is brighter and has more detail in the shadows. The disadvantage is the noticeable graininess of the image. The same is true in the photos below. 

ISO: 6400, 200

I can set my camera to choose the best ISO from a specified range. The available ISO values are 100, 200, 400, 800, 1600, 3200, 6400, and 12800. I usually keep it set at 100-200 and adjust the aperture and shutter speed based on the exposure I want. 

Try This At Home

First thing you need to do: find your camera’s manual and learn how to adjust the ISO. Then find an area with shadows. With your camera in auto, take a picture with a low ISO and then one with a much higher ISO. Look at the differences in the images. Which one is more appealing to you? Why? In my examples above, I like the photos with less grain. I always try to minimize graininess, but some people like it on occasion.  Post your images on your website, blog, Instagram, Facebook, Twitter, or whatever. Then, come back here and leave a link in the comments so we can see your photography prowess. 

Does this clear things up a bit (in your mind and your photos)? Do you still have questions? Be sure to ask, I’ll be responding to all comments. Or email us here. Got a photo tip? Let us know! We ♥LOVE♥ feedback here at Wordsmith Studio!! 

Go back and check out our earlier posts: Overview to ExposureAperture, and Shutter Speed. And be sure to come back in two weeks for some tips on photograph composition.

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