ISO: A Crash Course

​There are three basic principles of photography, one of which we talked about a few weeks ago. ISO, Aperture, and Shutter Speed are often called the holy trinity of photography because they control almost everything needed for the composure of your image. I already talked about how aperture affects depth of field and the focus area of a photo. Today I will teach you about ISO and later we will go over shutter speed.  

courtoisy of the SLR lounge

​ISO is how sensitive to light your camera’s sensor is. It originally meant how sensitive film was to light, when digital cameras came around the principle was applied to the sensors in them. Smaller numbers (ISO) have a lower light sensitivity as where higher numbers have a greater light sensitivity. ISO affects how exposed your picture will be and it works in conjunction with shutter speed and aperture to do this.  If you want to use a small aperture and fast shutter speed changing the ISO will allow you to get a proper exposure. A lower ISO level gives you a darker image due to the sensor being less sensitive to light. A higher ISO level gives you a lighter image due to the sensor being more sensitive to light. So say you're shooting at a concert and you're using f1.8 and a shutter speed of 1/200sec then the only way to make sure you get a good exposure is to use higher ISO levels 1600 or higher.

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​The shooting conditions you find yourself in will determine what ISO level you use. Higher levels are generally done in indoor locations and night time photography because these are low light situations. You need the higher sensitivity to pick up what little light you have.  Keep in mind that the higher the ISO level the more grain or noise will be introduced into the photo. 

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​For outdoor daytime shooting, it’s best to use lower ISO levels because there's a lot of light. You don’t want to overload the sensor which will over expose your photo. An over exposed photo is really hard to fix. It’s best to start out at your cameras lowest ISO level and work your way up as needed. 

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Grain is something that can add to a photo or take away from it. A little grain in a black and white can add a new depth to the photo that you never expected. If you have read my other blog articles then you know I’m a big advocate of experimenting and playing around with your camera. The best way to learn how to use grain to help you is to play with ISO. Use your camera inside your house at the different upper-level ISO’s then take it outside and use it at the different lower level ISO’s.
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There are certain things you should ask yourself every time you start to shoot; how much light do I have?, is the subject moving?,  and do I want to have grain in my shot or not?  These factors will influence what ISO level you use. Learning which levels to use when will help you to become a better photographer. 

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