How to achieve proper exposure using aperture, shutter speed and ISO
Photography is an art form, yet there’s a lot of technical knowledge involved to be able to capture light the way you see it and how it reflects off of the world around us. To master photography is to know the technical foundation well – so let’s go back to the basics of photography!
In this blog post, I’m going to talk about the basics of exposure – how to measure it and how to get the correct exposure.
Exposure
The very basic understanding of photography is exposure. Exposure encompasses the overall image and it determines how light or how dark the whole image is. When we talk about exposure, we're really talking about the lightness or darkness in the image.
You can measure your exposure through the light meter in your viewfinder. Your camera automatically measures the light wherever you point your lens, based on the settings you have on your camera. When your meter is at zero or centered, it means it's not underexposed or overexposed – it is exactly the perfect exposure.
The way we control exposure is through three main dials on our cameras: shutter speed, aperture and ISO. To understand exposure, think of it like a little triangle, and remember that all of these settings are related to each other.
Shutter speed
The shutter speed is meant to freeze motion. It’s physically in your camera as the speed by which your shutter curtain opens and closes to let light in. The longer you keep that curtain open, the slower the shutter speed, the blurrier their image is going to be, and vice versa.
Shutter speed is always going to be measured in intervals of a second. For example 1/60 is one sixtieth of a second, and 1/500 is one five hundredths of a second. The general rule is the bigger the number after the /slash, the faster it’s going to be. In example above, 1/500 is much faster than 1/60.
Aperture
Aperture is the size of the opening on your lens that allows the light through. Unfortunately, it's a little bit backwards to remember, but the smaller the number, the bigger the aperture – f 2.8 is bigger than f 5.6.
Your aperture size also affects your depth of field, which you can use creatively. The larger the aperture, the less light you let in, hence a shallower depth of field with a blurry background and sharp foreground. A wider depth of field needs more time for light to come through, and results in a sharp focus of both the foreground and background.
ISO
ISO is the sensitivity of your camera sensor to light. The lower the number, the higher the quality of your image, so try to keep your ISO as low as possible.
That's because when you increase your ISO, your sensor pixels become more sensitive to light to get as much of it as possible. However, this results in grainier photos. That's why you should think of ISO last because it compromises the quality of your image.
It’s best to set your ISO manually and start low at 100 or 200. When you’re in a situation where you’ve tried different settings to get the best exposure, but you still don’t have enough light, then you can dial up your ISO.
They’re all related!
As you can see, these three camera settings work together to create the perfect exposure!
If you think about exposure as filling a cup with tap water, the size of the faucet is the aperture and the shutter speed is how fast the water is coming through the tap. The larger your faucet opening, the quicker you must open and close the tap to prevent your cup from overflowing, and the smaller your faucet, the longer you need to leave the tap open to fill your cup. If you switch your cup to one that is shallower or deeper, you’ll have to change either the faucet or your timing to ensure you don’t over or under fill your cup.
When you’re shooting, try to remember: when one goes up, the other ones have to come down to adjust for light – just like in the water tap analogy!
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