All photographs, whether shot with an old film camera or the latest DSLR, are built using the same three components: ISO, aperture and shutter speed. Do you understand these three building blocks of photography, and how they relate? Below we’ll examine the ‘magic three’ and how to properly control them in your shooting.
First, some definitions:
ISO—the relative ‘speed setting’ for your camera’s light meter.
APERTURE—the size of the ‘hole’ that you create in your lens for light to pass through.
SHUTTER SPEED—how long you let leave that ‘hole’ open to light during the exposure
Let’s look at each of these in detail now.
ISO—the relative ‘speed setting’ for your camera’s light meter—This number used to represent the ‘speed’ of the film you were using; now in the digital age it’s still important. The lower your ISO number, the finer the detail that will be rendered in your image. Sounds good, right? But here’s the catch: The slower ISO settings require MORE LIGHT to create the exposure…which means slower shutter speeds—maybe so slow that you can’t freeze any action in your shot. So here’s the first of our Yin/Yang relationships: photography involves balancing a bunch of these tradeoffs!
APERTURE—the size of the ‘hole’ that you create in your lens for light to pass through–The bigger the hole, the more light will travel through at any given shutter speed, right? Lower aperture numbers, like f1.8, f2.8 and f4 represent LARGE holes, which also create the bokeh effect (out of focus backgrounds) that are stylish right now. SMALLER apertures, like f16, f22 or f32, represent VERY TINY holes which also will render your scene with much more of the scene in focus—maybe a good thing, maybe not.
SHUTTER SPEED—how long you let leave that ‘hole’ open to light during the exposure—Shutter speeds are displayed in fractions of a second, such as 1/60th sec, 1/250th sec, etc. The faster the shutter speed, the more action-stopping power in your image. So a photograph of a football player diving through the air will look crisp and clear if shot at 1/2000th sec, not so much at 1/250thsec.
Now that we’ve laid out these three building blocks, let’s look at how they interact with each other.
I usually make a decision about ISO first. Here’s why: I always want my images to have the finest detail possible while still allowing me to make the shot I want. So if I’m shooting a quiet still life detail outside on a tripod, I can set my ISO to 50—the lowest setting on my camera—and know that I can choose a long, slow shutter speed with a small aperture to get everything crisp and clear in my image. However, let’s say I’m shooting a sporting event in an indoor stadium under artificial light. Here I know I’m going to need to stop action in relatively low light, so I’ll begin by setting my ISO at 1000 to 1600, thereby letting me shoot at fast shutter speeds.
Now with my ISO set, I’ll think about the aperture and shutter speed I need. Let’s stick with the two shooting situations I described above. In the case of the still life, I want everything in the scene to be rendered in crisp detail, so aperture is my top priority. I’m on a tripod and there’s no movement to worry about in the shot. So I can use a long, slow shutter speed, allowing me to use a corresponding small aperture—say f16—thereby rendering everything in focus in this shot.
With the sporting event in the indoor stadium, my chief concern will be stopping the action in the photos, so shutter speed is my top priority. I’ll want a fast shutter speed—maybe 1/2000th sec—with a large aperture—probably f2.8 or f4—to make the player I’m focusing on ‘pop’ against the out-of-focus background.
It’s important to understand that many shutter speed/aperture combinations will create the exact same correct exposure, but the images may look different. Here’s what I mean:
1/250th sec @ f2.8 = 1/125th sec @ f4 = 1/60th sec @ f5.6 = 1/30th sec @f8 = 1/15th sec @ f11
Starting with 1/250th sec. exposure above, you’re making each shutter speed TWICE as long but cutting the light IN HALF with each change in aperture. So the same amount of light ends up getting exposed to your CCD with each of these exposures.
Learning to balance and use these variables is at the heart of all successful photography.
So next time you go out to shoot, take a moment to consider how you want to employ these three ‘building blocks’. Start by making a decision about your ISO, based upon what you’re shooting. Then think about aperture and shutter speed—which should be the priority? Once you’ve considered how you’ll handle these three, you’re ready to make some killer images.
Hi, I’m Andrew Boyd, a.k.a. The Discerning Photographer, and I hope this post has been interesting and informative. Please leave me a comment about it, let me know what you’d like to see more of on the site! You can also sign up for email delivery of all future articles or my RSS feed. Or subscribe to our Facebook page or our Twitter feed. Thanks!–DiscerningPhotog