When we talk about stops in photography, we’re referring to exposure and exposure settings. It’s a useful term for describing changes in the exposure for either aperture, shutter speed or ISO. It’s also not as complicated as it sounds and there’s a really simple way to work it out if you’re not a numbers person.
If you’re shooting in auto or program mode, a stop in photography exposure won’t make much difference to you, because the camera sets the exposure for you. However, knowing about stops in photography is essential if you use:
- aperture priority
- shutter priority
- manual mode
What is a stop in photography?
A stop in photography is not an exact number or setting. We refer to camera exposure settings changing by a stop, either up or down. When you increase the exposure by a full stop, you double the amount of light entering the lens and when you decrease by a stop, you halve the amount of light.
Of course aperture, shutter speed and ISO affect different aspects of exposure and are adjusted with different settings. However, any full adjustment of any of these three settings will affect the exposure by a stop, either up or down.
Further reading: How and when to use exposure compensation
How do you change stops in photography?
Did you notice that I said a full adjustment? Well, that’s because you can adjust stops in photography by a half and even a third at a time, not just by a full stop.
It’s up to you to decide by how much you’d like to adjust exposure at a time and you can set this on your camera. Every camera brand is different, so you’ll need to have a look at your manual to find out how to do it on your camera. On my Nikon, it can be done by:
- Selecting Custom Setting Menu
- B Metering / Exposure
- B2 EV steps for exposure control
- Then select 1/3 step, 1/2 step of 1 step
I like to have mine set to 1/3 so that I can make small adjustments to the exposure. To adjust either aperture, shutter speed or ISO when I turn the dial, the setting changes by 1/3 stop. If I want to make a full stop change, I simply turn the dial three notches.
That’s the simple way to work out stops – no math involved.
How do you know what your camera is set to?
A quick way to check, without going into the menu, is to move either your shutter speed, aperture or ISO dial and then see how much the setting changes. If, for example, your shutter speed is set to 125 and you adjust the dial up one notch:
- and the shutter speed changes to 250, it’s set to full stops
- if it changes to 180, it’s sets to half stops
- and if you get 160, it’s set to third stops
Now let’s have a look at stops in photography for each of the exposure settings.
This shot was overexposed – the sky is blown out and I wanted more tonal contrast between shadows and the rays of the setting sun on her so I adjusted my shutter speed for the next shot. Camera settings: 1/800, f3.2, ISO 500
What is one stop in shutter speed?
Talking in full stops, when you look at your camera as you adjust your shutter speed, every time the number halves, the shutter speed will be a stop slower.
If your shutter speed is set to, for example, 1/125 and you increase the length of time the shutter is open by one stop to a slower shutter speed of 1/60, it doubles the amount of time the shutter is open. More light enters the lens, so the exposure will be one stop brighter.
On the other hand, if you decrease the shutter speed by a stop to 1/250, you halve the amount of time the shutter is open. Less light enters the lens and the exposure will be one stop darker.
To bring down the exposure I reduced the shutter speed by two thirds of a stop – I turned the shutter speed dial down by two notches. Camera settings: 1/1250, f3.2, ISO 500
One important point to note is that these numbers are approximate. Half of 125 is 62.5, not 60. However a shutter speed of 1/60 is considered half of 1/125. I think this is where some confusion comes in with new photographers, so my advice is not to get too hung up on the exact numbers.
Remember, you don’t need to work out the math. If your camera is set to 1/3 step increments like mine, just turn your shutter speed dial 3 times and you know you’ll have increased or decreased the exposure by a stop.
Again, you’ll see that the math isn’t exact. The important thing to understand is the concept of stops in photography, rather than the exact numbers.
You’ll find this downloadable shutter speed chart really helpful in understanding the difference between full stops, half stops and third stops.
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What is one stop in aperture?
Like with shutter speed, aperture is measured in stops. Again, this can be full stops, half stops and third stops. And before we get into the details, bear in mind too that the math isn’t always exact with aperture either. You don’t have to be a mathematician to work it out though, just turn the dial on your camera.
Whatever EV (exposure value) step you’ve set your camera to will be the same for aperture. So if you’ve set your camera to 1/3 step increments, every time you turn your aperture dial one notch, the exposure will change by 1/3 of a stop.
There’s one area where adjusting aperture differs from shutter speed. Unlike with shutter speed, where the camera determines the minimum and maximum shutter speed you can use, with aperture the lens you use controls minimum and maximum f-stop.
This is one of the reasons why more expensive lenses are so desirable – the maximum aperture can be as much as 4 stops wider than a kit lens. So it can be used in lower light than a kit lens and can also produce a far shallower depth of field at its maximum aperture, which is why they’re so popular with portrait photographers.
Further reading: Expensive lens or expensive camera – which is better?
Camera settings: 1/1600, f4, ISO 200. Focal length: 120mm.
How do f stops work?
The first thing to remember about f-stops is that the number is actually a fraction, even though it doesn’t look like it, which is why f4 is smaller than f2.8. Just remember big number, small opening, small number, big opening.
The wider the aperture, the more light gets in and the shallower your depth of field will be. Also, because of all that light getting into the lens, you can increase your shutter speed.
Like with shutter speed, every full adjustment, results in halving or doubling, depending on whether you decrease or increase the aperture by a stop.
Full stop apertures are: f1.0, f1.4, f2, f2.8, f4, f5.6, f8, f11, f16, f22
So, for example, going from f2.8 to f4 is a one stop difference.
Further reading: What does aperture do in the exposure triangle?
What is one stop in ISO?
In the case of ISO increasing or decreasing, the setting doesn’t actually change the amount of light that hits the sensor, but rather the sensor’s sensitivity to the light. The end result though, is that it impacts the brightness of your image.
By now you’ve got the hang of the concept of doubling and halving when you adjust an exposure setting, and it’s the same with ISO. When you increase the ISO by a full stop, you double your camera’s sensitivity to light. When you decrease by a full stop, you half your camera’s sensitivity to light.
The ISO stops are really easy. ISO starts at 100 and doubles with the increase of each full stop.
Like with shutter speed and aperture, if your camera is set to increase EV (exposure value) adjustments in 1/3 steps, as you turn the dial on your camera, each notch will result in an increase or decrease of the ISO setting by 1/3.
Further reading: What is ISO for in the exposure triangle?
Stops in photography conclusion
So when you change your exposure by a stop, you’re either halving or doubling your shutter speed, or aperture or ISO.
You don’t have to make a full stop adjustment, but to make either 1/3 or 1/2 stop adjustments, you need to ensure that your camera is set up to do it. Do this using the menu system of your camera and it will apply when making adjustments to any of the three aspects of the exposure triangle:
- Shutter speed
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By Jane Allan
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