Understanding ISO: The Basics - Learn Blog Photography

Understanding ISO: The Basics

By Amy

May 24

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understanding ISO

Understanding ISO

Are you trying to grasp the concept of understanding ISO?  Have you wondered what ISO stands for? Understanding what ISO stands for, which is International Standards Organization, actually won’t get you any closer to understanding what ISO actually does.

When I was trying to learn how to shoot in manual mode on my DSLR, I felt SO lost.  I had no idea how to figure out what I needed to do to get something halfway decent.  Thank goodness for the digital age! I could’ve never afforded the cost of film for the amount of mistakes I made!!

I have a friend who told me all he did was play with the settings and watched to see the results he obtained in order to figure out how the camera worked.  I learn by doing, but that’s not the method that works best for me.  I need to know what I’m doing and then fiddle around for the results.  That being said, once I learned what ISO is and the connection is plays in the exposure triangle it made much more sense and I could use a more targeted approach to my fiddling.

So let’s dive into the nitty gritty so we can actually start understanding ISO.  ISO refers to the camera sensor’s level of sensitivity to light.

The lower the number, the less sensitive it is and thus creates a darker image.  The plus side to this is that a lower ISO level will create crisp, clean images with less noise or grain.  The higher the number, the more sensitive the image is and thus creates a brighter the image.  Unfortunately, the higher you go with ISO, the grainier or noisy the picture will be.  Here’s the same location with an ISO of 100 and taken again with an ISO 2000.  Look in the sky, can you see the boxy pixelation?  That’s the grain or noise I was talking about.

Understanding ISO

ISO 100



Understanding ISO

ISO 2000

Now don’t get me wrong…most cameras handle higher ISO pretty well, but each camera is different.  The best way to find out would be to either Google your camera (I’m sure someone has tested this) or to set up a test in your home and find out at what level you can detect the noise and or better yet, at what ISO setting you are comfortable shooting at before the noise becomes too much for your taste.  

Understanding ISO is just one important aspect of the exposure triangle.  The other two factors are aperture and shutter speed. It is the combination of these 3 factors that create a well exposed photo.  In general, you want to adjust aperture and shutter speed before the ISO.  If you’ve set aperture and shutter speed to what you want, but still don’t have enough light in the scene for a well exposed photo then I would increase ISO.  However, if you have all three set and you still don’t have enough light, then you will need to add flash, but that’s a story for another time.

If you keep your camera in AUTO mode or any of the program modes (with the exception of M) such as A, P, flower, running man, etc; your camera will automatically pick the ISO it deems needed for a well exposed photo.  Keep in mind, it will try to keep the lowest ISO possible, but if there isn’t enough light, then it will have to increase or you’ll need to add light such as flash.

I hope this sheds some light on the subject… HAHA pun only semi intended!  I created a SUPER helpful cheatsheet that you can download and save on your phone or print out.  If you want to get it click this link below!  Best part is…its FREE!

Understanding ISO and the balance with shutter speed and aperture is very importance in using your camera in manual mode.

If you have questions, feel free to comment below and I’d be happy to answer them!

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Download you FREE ISO Cheat Sheet HERE!

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About the Author

Amy is the owner extraordinaire at Learn Blog Photography and Amy Paris Photography. She's a single mom to an amazing teenage son. She's passionate about photography and skiing (downhill), the faster the better! Sign up for a FREE 30-min call to light up your photos & biz! bit.ly/2udzBXB