Exposure is something many people have encountered before. One can find it on most photo editing programs as a dial or bar that tweaks the brightness, yet most have no idea what exposure actually means for photography. Beginners, such as myself once upon a time, will often leave their cameras on the automatic setting or will simply shoot with their phones which renders the issue of exposure null. However, the first step towards maturity as a photographer comes with mastering the art of exposure, which will allow for more creative and technical freedom and ultimately, better pictures.
Surprisingly, the exposure of a photograph is actually the sum of three elements: aperture, shutter speed, and ISO, otherwise known as the “exposure triangle.” Getting to know these will also involve getting to know your camera better. But how does a camera work exactly? Essentially, a camera is a small, dark room with only one window, the lens, from which light leaks in and hits a light sensor. As a picture is taken, a shutter comes down and blocks that single opening, and the picture is recorded on the light sensor.
First, the aperture is the hole through which light comes through that can widen or narrow much like a pupil. Similarly to the human eye, the more the aperture narrows, the less light can enter, resulting in darker pictures. In order to measure the diameter of an aperture, photographers use ƒ-stops, where the lower the ƒ-stop number is, the wider the aperture. So an aperture of ƒ/4 would be considerably wider than ƒ/22, with some lenses going even as far as ƒ/1.4 or ƒ/45.
The first picture was taken at ƒ/25 and the second at ƒ/1.4. The latter is very obviously brighter than the former, which contains silhouettes. Once you start shooting in wider apertures above ƒ/5.6, something interesting happens. These two pictures were taken at about the same distance from the subject, but only the second one shows any signs of focus smearing. This is because the aperture also affects something called a picture’s “depth of field,” or the background blur. The wider the aperture you shoot with, the shallower your depth of field will be since light will have an opportunity to “spill” over the light sensor, thus creating more background blur. This makes wider apertures perfect for emphasizing a single subject and smaller apertures for placing the entire frame in focus.
Second, the shutter speed determines how quickly the shutter will come down when taking a picture. The speed of the shutter doesn’t actually change, only the delay with which it comes down after depressing the shutter button. Photographers measure this delay in seconds. Most cameras will support speeds between 1/500 second or 1 second, while some support as far as the blazing fast 1/8000 second or the slowest 30 seconds. Because the speed of a shutter affects the amount of time in which light can hit the sensor, it also affects the brightness of the picture.
The first picture was taken at a speed of 1/4000 second and the second picture at 1/2 second. While shooting the latter, I was sitting in a moving car, and because the longer exposure causes the light to hit the sensor longer, the image looks more like a horizontal smear, giving it a sense of movement with motion blur. However, as the shutter speed increases, the amount of motion blur decreases. With this effect, the running water in the first photograph feels frozen in time, which can offer a fresh perspective on the rapidly moving world around us.
Finally, ISO, the crux of the triangle, indicates the sensitivity of the light sensor. Its measurement primarily goes on a scale of 100, the least sensitive, to 6400, the most sensitive. Additionally, raising the ISO speed for more brightness comes at the cost of image quality since this causes the picture to appear grainier, although this becomes less of a problem with each new generation of cameras. Camera manufacturers will leave this setting automatic by default; however, you can tweak the ISO speed to get unique results without having to alter the aperture or shutter speed.
There is still so much to talk about regarding these elements as well as the multiple other facets of photography, but hopefully, this covers the basics well enough. I can’t wait to share more of what I’ve learned on my journey as a photographer.