Introduction
Let's learn together what shutter speed is in photography and how to set it to achieve either perfectly sharp images or artistic motion blur. Every photo needs its ideal exposure time; let's find out which one!
What Is the Shutter Speed?
In photography, there are two parameters that affect you photos the most: exposure time and lens aperture. In this article, we'll focus on shutter speed, explainig in easy words what happens after you press the shutter button.
Every camera has a sensor that captures light. Today it's almost always digital, but it can also be a film. When we take a photograph, we expose the sensor to light; the sensor is then impressed, which simply means it records the amount of light that hits it.
Forgive the oversimplification, but imagine the sensor as a collection of tiny buckets, technically called photodiodes, being filled by a shower of sand. The longer these buckets remain under the flow of sand, the more they fill up, eventually to the point of overflowing.
In the same way, each individual photodiode, or each pixel on the sensor, can fill up with light. To get a photo, you have to let light pass through for long enough to fill the photodiodes to a measurable level, but not so much as to fill them completely, otherwise the photo would turn out completely white.
Beneath you can see an example, deliberately in low resolution, to better understand. Darker pixels have received less light, while brighter pixels have received more.
To control how long light is allowed to pass through, traditional cameras use a mechanism that opens and closes called the shutter. Smartphones, on the other hand, don't have any mechanism; the sensor itself resets its values and turns on and off for a precise amount of time.
Actually, the shutter mechanism is complex; there are also the mirror and the shutter curtains that should be mentioned, but to keep the article readable, we'll describe those technical details later, in the final chapter.
The Motion Blur
In the previous chapter, we understood that the sensor must be exposed to the light in order to record the image. When the amount of ambient light is big, as under the midday sun, a tiny fraction of a second of exposure will be more than enough. When the light goes down, exposure time has to be longer, sometimes even many seconds, as in the dark of the night.
If we want a perfectly sharp photo, both the camera and the subject must remain completely still while the sensor is capturing light. A shutter speed of just a few thousandths of a second, which is a very fast shutter speed but absolutely reasonable in bright sunlight, can freeze an arrow shot by a bow or the blades of a helicopter.
As the light fades, you need to use slower and slower shutter speeds. In this case there's the risk that the movements of our subject, or the shaking of our hand holding the camera, begin to be more and more noticeable. In this case we are talking of a blurry photo; to be more precise, we refer to motion blur.
Motion blur is normally considered a flaw, but in creative photography it can sometimes become a feature. Think of waterfall photos, the ones with the water looking like mist, or panning shots of vehicles, or the photos where lights become trails of light. As always, the only limit is your creativity.
Although long exposures and motion blur may sometimes be an interesting stylistic choice, our aim is generally to capture the sharpest image possible. In the next chapters we'll find out how we can achieve it; the next three are specific for reflex cameras. If you shoot with your telephone, you can jump directly down to the chapter about the tripod.
The Aperture
In this chapter we'll briefly explain some settings about aperture. If you find it hard to follow the subject, or you want a more in-depth article, we wrote one. You can find it below:
As a general rule, when you're shooting in low-light conditions you should use the widest aperture available, so that as much light as possible can reach the sensor. On the other hand, if there's too much light, you'll need to stop down the aperture, otherwise your photos will end up overexposed, which means too bright. When it comes to these two extreme situations, there isn't much more to say.
There are other situation where you have total control and you can choose any aperture value you want. In this cases, in order to get the sharpest photo possibile, the golden rule is to always stop down at least a couple of stops, to help the lens perform better.
In very general terms, and oversimplifying a bit, the sharpest results are usually achieved at around f/11. It's a relatively small aperture, meaning it lets in less light, but in full sunlight, or using a tripod for stability, you'll be able to achieve a level of sharpness and maximum depth of field that would otherwise be impossible.
Stopping down the aperture is always the right choice when there's plenty of light, or if you have a stable support. But when shooting handheld, choosing the right shutter speed becomes far more important, as we'll see in the next chapter.
Recommended Shutter Speeds
When we talk about handheld photography, there's a rule that says that the shutter speed needs to be roughly equal to the focal length. Let's see what that means: when you use a wide-angle, let's say a 24 mm, you should set a speed of at least 1/30 or faster. If you are using a normal lens, such as a 50 mm, the shutter speed should be at least 1/60 of a second. If you decide to use a 200 mm telephoto lens, you should use at least 1/250.
These settings are meant for a decent photographer with a rather steady hand. If you are a newbie, this estimate is a little too optimistic, and we'd prefer to play it safe by using shutter speeds at least one stop faster, especially with telephoto lenses.
In sports photography, shutter speeds must be very fast. In just a few hundredths of a second, subjects move significantly, so it's recommended to use at least 1/1000. Even better, stay faster to avoid motion blur. You can try to lower the shutter speed to around 1/500 only if the subject is moving toward you.
When you have to photograph water, you need to choose: if you want the water perfectly frozen, you should stay around 1/500. If you want a sense of motion, at 1/30 you will start to see a slight streaking effect. From 1/3 onward, the effect becomes increasingly visible. If you want to photograph rain, 1/60 of a second is the best shutter speed to capture raindrops of the right length.
Every photograph requires the right settings. Sometimes shutter speed is the least of your concerns; other times you'll need to squeeze every bit of performance out of your camera. In the next chapters, we'll look at how to handle different shooting conditions.
ISO sensitivity
We've often mentioned that, in some situations, we're forced to use fast exposure times. But imagine a situation where light is scarce, and even with your aperture at its widest, the shutter speed is still too slow for your needs.
In this case, it would be extremely useful to be able to "force" the camera to decrease the exposure time. This is exactly what ISO sensitivity allows us to do. The standard base value for most sensors is ISO 100, with a few rare exceptions not worth mentioning.
This parameter can be increased as needed. If a photo requires a one-second exposure at ISO 100, setting ISO 200 will halve the time. Using ISO 400 will reduce it to a quarter, and so on.
Forcing the camera to use higher ISO values has a downside: digital noise. In this case the word "noise" is a synonym of a "grain" on the photo, more and more noticeable using higher ISO values. You can see an example in the photo below.
There are several things that have to be said about digital noise, the first of which is that it should be avoided, using high ISO values only when they're really needed. On the other hand, a noisy photo is always better than a blurry one. If you have to take a photo of your friends lit by the soft glow of a campfire, don't fear the noise; use even ISO 12,800 if needed. The picture will be grainy, but at least you got the shot.
It also has to be said that there are many software for noise reduction, also called denoisers, which sometimes do wonders. The best ones aren't free and are based on AI, but any camera manufacturer has its own free software. When you apply noise reduction to a photo, it will inevitably lose some detail, but when the picture is meant to be displayed on a screen, denoising is always the best choice.
On the other hand, when a photo is printed, the digital noise is dramatically less noticeable than what may appear on your display. If the photo is meant to be printed, we suggest trying one test print without denoising; you'll probably be stunned by the result. For small or medium size prints, it's good practice to avoid noise reduction; the loss of detail gives worse results than noise does.
The Tripod
We've seen that if we want to achieve the highest possible image quality, we need to use the lowest ISO setting and stop down the aperture, but this inevitably leads to longer shutter speeds. Considering that the main cause of motion blur is the natural shake of our hands, the only way to get a perfectly sharp photo with relatively long exposure time is to use a stable support.
Placing your camera on a solid surface, or even better, on a tripod, is the most effective way to avoid unintentional movement. Since a tripod should be as stable as possible, you should avoid extremely cheap models. In strong wind conditions, it's common practice to hang a weight, such as a backpack, under the tripod; if you need to buy a new one, make sure it has a hook for this purpose.
Your photographer skills has to be used to decide whether a tripod is the best choice or not. For example, if you need to shoot at an event, you'll want to be as mobile as possible, so a tripod is definitely something to avoid. In that case, you'll need to open up the aperture or use faster shutter speeds with higher ISO settings.
On the other hand, for landscape photography, using a tripod is always the best option. It allows you to use the lowest ISO possible, a properly stopped-down aperture, and longer shutter speed.
Since the best landscapes are usually photographed during the golden hours, just before sunset or shortly after sunrise, light is not sufficient for handheld shooting, unless you're using a stabilized lens, a topic we'll cover in the next chapter.
Image Stabilization
Nowadays most high-end phones and lenses offer a handy feature: image stabilization. It's a gyroscopic mechanism that physically acts on the sensor or on the lens, designed to drastically reduce hand-induced shake.
Using different words, it's a technology that allows you to obtain sharp pictures even using reasonably longer shutter speeds, essentially a couple of stops. A photo that would normally be blurred may become almost perfectly sharp. Obviously it's a technology that has to be used only while shooting handheld; if you're using a tripod, you absolutely have to disable it.
Explaining stabilization in more detail would only turn it into a complicated, boring, and a little controversial topic. Let's spare ourselves those tedious digressions and just say that, for the average user, it's a very useful feature. It won't work miracles, but it lets you use reasonably longer shutter speeds handheld, a welcome help when the light is low.
The only "tiny rant" we have to tell you is that a photo taken with stabilization will never reach the same level of perfection, in terms of sharpness, as one taken with a tripod and flawless technique.
Mirror, Shutter, and Shutter Curtains
This final chapter is about a topic that concerns only SLR cameras. The reasons we're covering it are both the technical explanation of what happens after you press the shutter and the fact that we've often written about the perfection in terms of sharpness, and this is the last piece of the puzzle.
Traditional SLR cameras have a mirror, which is exactly what the name suggests: a mirror. When you look through the eyepiece, what you see is the actual light that passes through the lens. This happens thanks to the mirror, in red in the illustration below, which reflects the light toward a pentaprism, where it's corrected and directed to the viewfinder.
When we press the shutter button, the mirror must be raised in order to allow the light to reach the sensor, in green in the image below. After that, it's the time of another mechanism, the shutter curtains, whose work is to perfectly control the amount of light that is allowed to pass through. The shutter curtains are really lightweight, while the mirror is definitely heavier.
Obviously, the mirror is a feature unique to SLR and DSLR cameras. Mirrorless cameras don't have one, although they still use a shutter curtain, while smartphone cameras have neither.
The more perceptive among you will have already guessed the issue: when it flips up, the mirror creates tiny vibrations. Since we want the absolute perfection in sharpness, it's not enough to set the lowest ISO, choose the ideal aperture, use a solid tripod, and disable any stabilization. You'll also need to enable mirror lock-up.
It is a setting that tells the camera to raise the mirror a little before actually shooting. The only way to make it work is to associate it with a self-timer. The ideal procedure for a panorama photo with impeccable sharpness will therefore be:
- Choose a day with no wind.
- Mount the camera on a tripod.
- Set ISO 100.
- Stop down the aperture, ideally to f/11.
- Enable mirror lock-up.
- Set a two-second self-timer, or whatever delay you prefer.
- Press the shutter button; the camera will raise the mirror.
- Two seconds of nothingness, during which you remove your hands from the camera, stay perfectly still, stop breathing, and don't even blink.
- The camera takes the perfect shot.
If you're chasing perfection, the only exception to this procedure is that you're allowed to blink; just do it gently. Jokes aside, check specialized websites for the ideal aperture value for your lens; f/11 is a general guideline, and while it's often correct, some lenses perform best at different settings.
Conclusion
We hope you liked this page about shutter speeds in photography. Before saying goodbye, we would suggest you read all the articles we wrote about photographic technique.
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