ISO Tutorial – Summer Photography Series

Summer Photography Series, Week 2

Summer Photography Series at 5 Minutes for Mom

Remember the days before digital cameras? It seems like ages ago when I would put film into the back of my camera whenever I wanted to take a set of pictures. When my roll of 24 shots was finished, I’d take the small canister to the photo department and drop it off to get developed.

Most of the time, while I was waiting for a roll to be developed, I would stare at the wall of new film to pick out a replacement canister for my next set of pictures. I often wondered which was the “right” box to buy for the pictures that I wanted to take.

I saw boxes labeled ISO 100, 200, 400, 800….. and I had no idea which one to pick!

What is ISO?

ISO literally stands for “International Organization for Standardization.”

Before the digital age, photographers bought their film in different “speeds.” The ISO number referred to the speed of the film, or it’s sensitivity to light. Although digital cameras don’t use film, the term ISO is still used to refer to a camera’s light sensitivity.

Instead of having to change your film for each unique lighting situation, digital cameras are able to adjust the ISO, or how they process the light coming in, internally. You can change your ISO each time you take a picture (but in general, I will change my ISO 1 or 2 times during a shoot). It’s one of the many things that I love about digital photography!

The ISO you use lets you know how sensitive the camera’s image sensor is to the amount of light present. The lower the ISO (say 200) the slower the speed of the sensor’s ability to capture light, the higher the ISO (say 1600) the faster the sensor’s ability to capture light. When your sensor is more sensitive to the ambient light, you are better able to take pictures in low-light situations.

Which ISO should I use?

I always try to use the lowest possible ISO (ie – 200 or 400).

Wait. Didn’t I just say that higher ISOs allow me to take pictures in low light situations? Yes, but those higher ISOs do come at a cost.

The higher the ISO, the more grain and digital noise you will notice in your pictures. Noise is not good. I like my pictures to be as crisp, clean, and as sharp as possible, so I only use a high ISO when I absolutely have to.

When outdoors, I usually shoot with ISO 100 or 200. If I am shooting something fast-moving (like a child), then I will go for ISO 200 to 400. On a cloudy day or in the later afternoon, I’ll usually use a higher ISO (400).

When I am indoors I typically use ISO 400 or 800, and often bump the ISO up to 1000 or even 1600 when I really want to snap a picture in a not-so-bright room without a flash.

High ISOs are especially helpful when taking pictures where flash is not permitted, such as a museum or a concert. I would much rather deal with a grainy picture than a blurry one.

Can you see the difference?

At first glance, the three images included in this post look the same. All 3 pictures of my niece were taken on the same day against the same wall, with the same general settings. The only thing that my sister changed was the ISO.

Notice that each of the 3 pictures is correctly exposed. However, look closely at the wall in the background and the edges of the butterfly mask. As the ISO gets higher, the wall becomes more grainy and the mask becomes less crisp at the edges. The photo taken at ISO 3200 is still a great picture…..but if you’re striving for clarity and detail, then the picture taken at ISO 160 is definitely the way to go.

ISO Challenge

This week’s assignment is to take a picture indoors without using the flash.

Just adjust your ISO until the lighting looks right and your subject is no longer blurry. This could take a little bit of trial and error, but it is definitely worth the practice. Be sure to come back to share your picture(s) and let us know what ISO you used and how it changed how your picture turned out.

If you have any questions during the week, feel free to ask. I’m always here to help!

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Written by 5 Minutes for Mom managing editor Lolli. You can find Lolli blogging at Better in Bulk and tweeting at @1momof5. Photos by Lolli’s amazing sister, Andrea, owner of Andrea Marie Photography and author of the blog DAVE family.


  1. says

    this was something that took me a long time to get my head around, but i went to a talk by a man who has been a professional photographer his whole life, and is now retired, and he said that a few years ago he switched his setting for ISO to auto, and has thinks that it is so good he virtually never changes it!

  2. says

    Thank you for the info. I never really knew what ISO was, or what affect using the different ISO numbers could do. Since I take pictures of the items I sell on my website, this information was really helpful! Thanks again!


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