Have you ever been in that situation where your image exposure is ok, but you can’t get it as sharp as you would like or with that nice effect you have in mind?
A friend of mine once told me: “The shutter speed is that thing you messed up when getting blurred images instead of sharp ones, and sharp images when you want them to be blurred.”
But what exactly is shutter speed in photography? This article will help you to understand how shutter speed works and how to master it, to squeeze the best from your photography.
What Is Shutter Speed?
Shutter speed in photography refers to the amount of time the camera shutter stays open to exposes the sensor to light, to record the image.
How Does The Shutter Speed Work?
The idea behind the shutter speed is simple: in low light conditions, you need more time to collect the same amount of light than in bright situations. Thus you need slow shutter speeds.
In bright daylight or when using a flash, the amount of available light is enough to allow a fast shutter speed.
So, how does this idea translate into practice? When you press the button to take a photo, the shutter inside your camera opens for a given amount of time.
And only during this time, the sensor is exposed to light and can record the image.
Traditionally, the shutter is a mechanical device that uses one or more movable parts to allow the sensor to expose to light the sensor (or film) only for the selected amount of time.
Electronic shutters are often used in camera phones and compact cameras.
DSLR and mirrorless cameras have a mechanical Focal-Plane Shutters, often coupled with an electronic shutter.
The Focal-Plane Shutter In DSLR And Mirrorless Cameras
This type of shutter is placed directly in front of the sensor, and it consists of two mobile curtains, one of which covers the sensor, thus preventing the light from reaching it.
At low shutter speeds, when you fire the shutter to take a photo, the curtain that was covering the sensor (1st curtains) moves out the way, exposing the sensor.
After the desired amount of time, the other curtain (2nd curtain) moves in, covering the sensor again.
At high shutter speeds, the two curtains move together across the sensor while being separated by a distance depending on the shutter speed.
In this case, the sensor is not exposed to light all at once, but a portion at a time.
Most cameras today use a vertical-travel shutter.
This is still a “two-curtains” shutter, but now the curtains move vertically, rather than horizontally, thus minimizing the distance to cover. This allows setting the shutter speed as fast as 1/16000th of a second (Nikon D1).
The main drawback of this design is that when using a flash, you cannot use a shutter speed faster than a certain value (called sync speed), or you will see the curtains in the image.
Electronic shutters allow you to use a shutter speed as fast as 1/32000th of a second.
They also have the advantage of being silent, as there are no moving parts.
How To Find It On A Digital Camera
In a digital camera, you can set the shutter speed with two operational modes: (i) shutter speed priority mode and (ii) the manual mode.The semi-automatic shutter speed priority mode lets you set the shutter speed while the camera adjusts the lens aperture (and the ISO if you use them in auto) to properly expose the scene.
With the manual mode, control both the shutter speed and the aperture: it is up to you to get the right exposure or the right creative effect you are after.
To set the shutter speed, you may have a dedicated dial, a button or menu, etc. If you are unsure, refer to your camera user manual.
Why Is Shutter Speed Important In Photography (Especially Astrophotography)?
Have you ever made photographs that were exposed correctly, but people came out blurred? Too slow shutter speed was probably why that happened.
In astrophotography, the shutter speed is, if possible, even more crucial, as it is responsible for the balance between the need to collect enough light and to have pinpoint stars for the best image quality.
The image below shows the open cluster NGC6871 in Cygnus: to get a hint of the faint Tulip Nebula (the red splash of color), I had to use a shutter speed of 180″ for each photo, and take 30 of them. At 400mm, having sharp stars that slow shutter speed is challenging.
Learning how to set the shutter speed in astrophotography is crucial.
Shutter Speed Is Part Of The Exposure Triangle
Shutter speed is one of the three ingredients making up the so-called exposure triangle, and together with the aperture and ISO value, it sets the exposure (brightness) of the photo.
But there is much more than getting the exposure right when it comes to shutter speed.
Effects Of Setting Fast Shutter Speed Times
The main effect in using a fast shutter speed is freezing any movement, both in the scene and with the camera, typically from the camera shaking when photographing handheld.
A fast shutter speed is particularly crucial with sports photography, and everywhere there is rapid movement: if your shutter speed is too slow, you’ll get blurred photos.
I realized that the hard way, the first time I was photographing dancers in a theatre. My widest aperture was still not wide enough, and my shutter speed was about 1/40th of a second, but still, I have 5-stops image stabilization in my camera, so no problem, right?
Wrong. Only when I lowered my shutter speed to 1/125th, I started to be able to freeze the dancers.
In portraiture with natural light, try not to go slower than 1/60th. I discover that people can’t stay perfectly still, and below 1/60th of a second, this can blur away the details.
If you are shooting handheld, to avoid camera shake, you should use a shutter speed equal to the inverse of the focal length you are using.
Say you are trying to photograph the Moon handheld at 200mm, for the sharpest results use a shutter speed of about 1/200th of a second or faster.
Image stabilization will let you take sharp images even with slower-than-recommended shutter speed, but remember: it only compensates for camera shake.
Effects Of Setting Slow Shutter Speed Times
The obvious effects of using slow shutter speeds are increasing the brightness of the image and introducing motion blur in it.
This is where you can get creative with the shutter speed by turning motion blur at your advantage to create a compelling image.
A set of neutral density filters, ND, of different strengths is a must-have accessory for creating long exposures. They allow you to take long exposures in broad daylight.
ND filters are also used in architecture photography to blur moving clouds, thus conveying a sense of motion.
How To Set It For Night Photography?
When it comes to night photography, you may think you always have to use a slow shutter speed, but this is not always true.
Consider astrophotography, for example.
What Is The Best Shutter Speed For Astrophotography?
Particularly in astrophotography, setting the shutter speed is quite a challenge, as the exposure time is limited by several factors other than the amount of available light.
How To Set The Shutter Speed When Using A Tripod: The 500 Rule
If you are trying to do astrophotography using a tripod, the limiting factor for the shutter speed is the apparent movement of the stars across the sky.
Because the Earth revolves on its axis of 360º in 24hrs, stars seem to move across the sky at a speed of about 15º each hour.
This means that too long exposures from a fixed tripod will show stars looking like short trails rather than a sharp point of light.
A set of empirical rules that I call N-rules gives you a rough estimation for the slowest shutter speed for which stars will not trail noticeably.
Those rules take into consideration the size of your camera sensor (the crop factor) and the focal length you use.
The rule reads like: SS = N / (CP * FL), where SS is the shutter speed (in seconds), CP the crop factor, and FL the focal length, and N is a number.
The most famous rule has N=500, and it is known as 500-rule.
So, how do those rules help us?
Say you are trying to photograph a starry landscape with a 24mm on Canon 60D. The camera has an APS-C sensor and a CP=1.6.
If you use the 500-rule, the slowest shutter speed you should use with this setup is 500 / (1.6*24) = 15s.
The 500-rule worked well for film and is still ok today for prints, but on screen, it shows its limit with modern high-resolution digital sensors.
Better to use the more conservative 400-rule: for the example above, the recommended shutter speed drops to 10 seconds.
With star trail photography, the wow-factor is in the trailing star, and in theory, you could expose as long as you want.
But because digital sensors suffer from thermal noise, it is best to limit yourself at 5-10 minutes exposures. Simply take a series of photos and combine them later on to get the final star trail image.
How To Set The Shutter Speed To Photograph The Moon
It seems easy, at first, to photograph the Moon, but have you ever struggled to get it sharp even when the focus was ok?
Assuming it was not camera shake, this is due to poor seeing conditions (atmospheric turbulence, haze, etc.), magnified by the long focal length you used.
The trick is to pick a clear night and to keep the shutter speed as fast as possible to freeze the atmospheric turbulence.
With the Full Moon, an empirical rule called Looney-11 says that the Moon is properly exposed when using an aperture of f/11, ISO 100 and a shutter speed of 1/100th.
Depending on the focal length used, a shutter speed of 1/100 can still be too slow. By using the exposure triangle, you know you can get the same good exposure using a shutter speed of 1/200th combined to an aperture of f/8 and ISO 100.
How To Set The Shutter Speed To Photograph Deep Sky Objects
Of all targets, deep sky objects (DSO) are the most difficult to photograph, mainly because they are faint and require long exposure to be revealed in a photo.
Because of the long exposure required for DSO, the ability to track the movement of the stars is crucial: a motorized equatorial mount is needed.
The shutter speed, in this case, is limited by the tracking accuracy of your mount and by the brightness of the sky due to light pollution.
A good rule of thumb is to set the shutter speed so that the peak of the histogram is about ⅓ to ½ of the range from the leftmost edge…
Once again, the idea is to take many photos to be combined later to create a more detailed image of your target.
In this article, we have covered the basics of what shutter speed is and how it can be used to create creative effects in everyday photography and how to use it in astrophotography. All it remains for you to do is go out there and experiment with this setting.