Mastering Manual Mode

The photography exposure triangle is a fundamental concept that every photographer should understand. It is the relationship between aperture, shutter speed, and ISO that determines the exposure of a photograph.

The aperture is the opening in the lens through which light enters the camera. It is measured in f-stops, with a lower number indicating a larger opening and more light entering the camera. Aperture also affects the depth of field or the amount of the photo that is in focus. For example, if you are shooting a single subject and want a lot of blur in the background, your aperture might be at f/1.2 or f/1.8. If you are shooting a large group of people where everyone needs to be in focus, your aperture may be at a higher number, like f/4 or f/6. If you are shooting a single subject (unless you want the background to be in focus), it is a good rule of thumb to leave your aperture at the lowest number possible, to let in the most light, and to keep your ISO low. Just keep in mind that this will also create a very blurry background, so it is not ideal for every situation and really depends on the look you are wanting for your photo.

ISO is the sensitivity of the camera's image sensor to light. It is measured in numbers, with a higher number indicating a more sensitive sensor and more noise (or grain) in the final image. ISO also affects the overall exposure of the photo, with a higher ISO allowing you to shoot in darker conditions. Think of a cat eye, with the pupil being your ISO. When there is sufficient light, the cat’s pupil gets smaller. When it is dark or there is insufficient light, the cat’s eye gets larger to allow the most light possible to enter its eye.

Just like a cat, your ISO must remain small when there is sufficient light. If you have a high ISO in bright light (like big cat eyes in direct sunlight), your photo will be too bright. This may often be referred to as over-exposed or “blown-out.” For example, a high ISO may be 1600, while the lowest suggested ISO is typically 100. Similarly, your ISO will be higher in low lighting to allow the most light possible to pass through. If you try to take a picture with a low ISO (the small cat eyes) in a dark room, your photos will be too dark or under-exposed.

Just remember big cat eyes in the dark. High ISO.

Small cat eyes in the light. Low ISO.

ISO affects more than just lighting! Having a high aperture will often cause your photos to be grainy, which is why you should always have your ISO as low as you can, while still allowing sufficient light to pass through. But how do we choose a high number to account for lighting AND a low number to avoid grain at the same time? This is where the exposure triangle comes in! Understanding the exposure triangle is essential for achieving the correct exposure in your photos. With practice and experimentation, you can learn how to balance aperture, shutter speed, and ISO to create the perfect exposure for any situation.

Shutter speed is the length of time that the camera's shutter is open, allowing light to enter the camera and expose the image sensor. It is measured in seconds or fractions of a second, with a slower shutter speed allowing more light into the camera and a faster shutter speed allowing less light into the camera. Shutter speed also affects motion blur, with a slower shutter speed resulting in more motion blur and a faster shutter speed resulting in less motion blur.

For example, if you are taking a photo of running water, and you do not want the water to appear blurry, your shutter speed may be 1/800. Whereas, if you want to create a blurring effect showing the movement of the water, your shutter speed would be set a lot slower, perhaps around 1/100.

A good rule of thumb for shutter speed is anything that moves should have a shutter speed of at least 1/250. The faster the subject moves, the faster your shutter speed needs to be to freeze the motion in your photo. For example, shooting a child may put your shutter speed at 1/500, while shooting a running cheetah would require a much higher number, perhaps 1/1000 or more.

If you want that gorgeous motion blur, then your shutter speed has to be lower than 1/250. A good way to think of it is not to put it lower than the focal length of your camera lens. So, if you are shooting with a 55mm lens and want to create motion blur, you would set your shutter speed somewhere between 1/60 and 1/250. If you were shooting with a 70mm, your shutter speed would be somewhere between 1/80 and 1/250. When shooting with a shutter speed under 1/100, it is ideal to use a tripod or to brace yourself in a way that will prevent movement or camera shake.

The exposure triangle is the relationship between these three elements, and adjusting one of them will affect the others. For example, if you increase your ISO to let in more light, you'll need to change your shutter speed or ISO to compensate for and maintain the correct exposure.