The Big 3- ISO, Shutter Speed, and Aperture

So you got yourself a fancy DSLR and you’ve been using it on the Auto setting. Once you’ve developed your comfort with composition, it’s time to graduate to shooting in manual mode and unleash the true power of the camera you are holding in your hands. There are 3 core components to setting up your camera for a shot. These settings are the ISO, shutter speed, and aperture, all of which affect the exposure or brightness of your photo. This post will go through each of these settings in depth and what specific effects each will play on how your photo will turn out. 

iso triangle

This is the simplest setting to understand and adjust. ISO stand for International Organization of Standardization which is quit the mouthful to say and isn’t really descriptive for what it does. The ISO setting is an adjustment on the sensitivity of the image sensor in your camera. Increasing this number will make the sensor pick up more light, making the image brighter. However, the drawback of increasing the sensitivity of the sensor is that it creates more grain in the image. ISO 100 is the lowest setting on most cameras and is considered the clearest image that you can take. ISO is often the last adjustment I make because I try to keep the image as clear as possible. I only raise the ISO in order to meet my light criteria if I am restricted on my settings for shutter speed and aperture. ISO can be adjusted in the camera body itself and is independent of the lens. The example below demonstrates the noise introduced at high ISO values. 





Shutter Speed
Adjusting the shutter speed will change how fast the shutter closes when you take a picture. The longer the shutter is open, the more light is able to hit the sensor, which will brighten the image. Motion in your shot will play an important role in choosing an appropriate shutter speed. If you are photographing something that is moving and you want a clean crisp image, the shutter speed will need to be set to a fast setting. A fast setting will decrease the amount of light the sensor receives so it will be important to adjust the other two settings in order to properly expose the image. If the shutter speed is set too low, you will start to see blurred edges, and the slower it is set the more motion is transferred into the image. Intentionally slow shutter speeds can be used in order to create various effects like ghost trails. This is the key component in a genre of photos deemed long exposure which use extended exposure times to get unique photographs. We will address long exposure in its own post later on (its one of my favorite topics). If your subject is stationary and you do not need to worry about introducing motion into the frame, slowing the shutter speed is a great way to increase the available light hitting the sensor. Just make sure you are using a tripod because any hand movement will transfer the motion into your photograph as seen below. This is another setting that is set by the camera body. 

Shutter speed of 1 sec with shaky hands

Aperture is tied to the particular lens you are using. Some lenses have a fixed aperture, and other have a range of apertures that can be adjusted. The aperture is commonly referred to by the F stop number and is marked as such. Aperture is the physical size of the opening in the lens that allows the light through to the image sensor. Counter intuitively, the large the F number, the smaller the opening. So an F22 lens would have a very small opening compared to an F1.8 lens. Besides the amount of light you let in, the aperture controls another very important effect on your image, depth of field. Depth of field determines which areas of the photography appear sharp. Higher F stops bring the background and the foreground  into focus whereas an F1.8 setting will isolate the foreground and blur the background. Landscape photographers look to use higher aperture numbers in order to make sure the entire shot is crisp and provide great depth to the shot. Shots that you want to isolate the foreground subject and add whats called a bokeh (blurry background), should be taken with a low F number. Low F numbers mean more light and translate to the ability to shoot at faster shutter speeds, making a zoom lens with a low fixed aperture important for wildlife photographers that want to capture subjects in motion. The two shots below show the difference between a large and small aperture for the same shot. 




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