Photography 101: ISO

What is ISO?

ISO numbers measure how sensitive the sensor is to light.  The lower the number the less sensitive (100 – 400) and the higher the number the more sensitive to light (800, 1600+).
On a bright sunny day, you will have your camera set at 100.  As things get darker, in the shade, inside, low lights, you will raise your ISO to make up for the lack of light.

Below you will see exactly how light is affected when changing your ISO.  I left all of my other settings the same except for my ISO so you can clearly see the difference. In this situation, I would shoot with my ISO around 400.


As a result the higher the number the more noise you get in pictures.  Noise is the grain that you see in pictures at times.  So to avoid noise keep you ISO as low as you can get away with. With most camera’s 400 and under and you wont notice a noise level.  Nikon’s are known for having a little less noise in low light. But overall both brands are amazing.noise

Some things to consider when choosing your ISO:

Do you have good light?
Do you want noise in your picture?
Are you using a tripod? You can get lower ISO number if you subject is stationary and can have slower shutter speeds.
If you are in a dark setting, and you need your shutter speed to be faster(shutter speed is our next topic) you’ll need to raise you ISO.


Indoor sporting event – Subjects are moving fast, and there is limited light available.
No Flash Zones- Plenty of shows, recitals, galleries where you can’t use flash you’ll need to have a higher ISO
Birthdays – Blowing out the candles, don’t use your flash, keep the mood and crank up the ISO.


Below I have a sample from a lower end DSLR and a Higher End DSLR.  A Canon t2i has an ISO range from 100-12800.  An entry level DSLR will show a larger amount of noise. As you can see at ISO 100, you have a very clear image and at 3200 you can see the noise. When you take a picture don’t just trust your LCD screen, zoom in and check your noise if you are worried.

With a 5D Mark III you can see how minimal the noise is even at ISO 8000.  The 5d Mark III has an ISO range from 100-25600.

*For you Nikon peeps out there, a Canon t2i is comparable to a nikon D90,  a T3i to a D5100. A Canon 5d mark III to a Nikon D800.


ISO, Shutter Speed, and Aperture all play off each other. Part of whats called the EXPOSURE TRIANGLE, they all go hand in hand. However, you need to learn each one individually before we can throw everything at you. Next time I will be teaching you about Shutter Speed.

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  1. says

    Hi Chelsea.
    I have been using a very regular camera from Fujifilm (Finepix S700) coz I did not want to chip in such a chunk of money into my camera. I design handmade greeting cards and a lot of DIY creative stuff and I blog about it. That’s where I need a good camera. Craft Gawker refused my submission purely on the basis of light of my photography. Hence I have been saving for nearly 2 years and want to invest into a good quality camera. Could you please advise me which camera I should purchase and how user friendly they are.
    Thank you very much
    Naush ~ Dubai

    • says

      Hello Naush. Later in the year I will be tackling Camera bodies and lens’s worth getting. So to keep it simple I will tell you that I am a big fan of outgrowing your gear. Starting simple and less expensive. I will never advise someone to just jump in and get the best camera they can. My first camera was a Canon Rebel t1i, it was a great way to start. I believe the current model is a Canon Rebel t5i, but I would get anything from a t3i-t5i to start. Also, I would not get a kit with a lens. But I would purchace the camera body and then a good starter lens is the 50mm 1.4 (or the more affordable 50mm 1.8) OR my everyday lens around the house and with my kids is the Tamron 28-75 (a more affordable version of the canon 24-70). It really depends if you want to be able to zoom, or use prime (where you have to physically walk in and out to zoom). If you keep following my posts I will get into more detailed reasons for getting certain lens’s and bodies. Hopefully for now that will help you out! I’m not as familiar with Nikons, so I hate to give to much detail on what bodies are there, but you can get a decent camera body for under $500 for sure. Also, if you can find it used in good condition, thats a great way to go. So many photographers like to upgrade when the newest stuff comes out and there are a lot of cameras in great condition that you can get at a lower cost.

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