In our third installment of the “how to” series Mastering Manual Mode we are going learn about ISO. The simplest definition of ISO is: it is your camera’s sensitivity to light. More specifically it is how sensitive your camera’s sensor is to light (the sensor is responsible for turning light into an image). Most cameras start measuring ISO at 100 or 200 and work their way upward from there. The LOWER your ISO number, the LESS sensitive the sensor is to light. The HIGHER your ISO number, the MORE sensitive the sensor is to light. So, how and why should this concern you?
Lower ISO numbers result in crisper and clearer pictures with little to no noise (how much grain you can see in your photograph). In general you usually want to use the lowest ISO you can in order to get a properly exposed image, so that the image is a crisp, clear and noise free as possible. But what if you can’t use a super low ISO (think 100 or 200) without compromising the target shutter speed or aperture? This is when you want to move your ISO to a higher number. Just be aware that your image might have more noise than you would like.
Setting your ISO properly can help you achieve super fast shutter speeds or a use a high aperture setting when there isn’t a lot of bright light available. For example, let’s say you need a shutter speed of 1/2000 or an aperture of f/11 and your photo needs to be properly exposed. With both of these settings there is a very small amount of light being let in to the sensor. By increasing the sensitivity of the sensor (ie, the ISO) you are increasing how much the sensor can record even though there is a small amount of light being let in. You may or may not be happy with the amount of noise a high ISO produces, but at least you are able to get a properly exposed image.
How high is too high? That will depend on your camera. Some cameras can only go up to ISO 800 before the photos have a lot of noise in them and some can go all the way up to ISO 2000 or higher without having a lot of noise. I encourage you to push your camera to high ISO levels to see how much noise you are comfortable with. If you have to push your ISO higher than you would like (and you don’t want a lot of noise) you might need to reevaluate your shutter speed and aperture to see if you achieve the same exposure without the noise.
*All photos taken by Tracy Cepelak of Tracy Lynn Photography