Every camera, since the very first pinhole models, has a shutter. The shutter is the device that regulates the duration of time that light hits your photographic medium. The principle of the shutter has not changed since the dawn of time. Or at least, the dawn of photography.
The shutter opens; light hits the photographic medium, the shutter closes; and light stops hitting the photographic medium. The longer the shutter stays open, the more light reaches your film – It’s as simple as that.
If too much light hits your photographic medium, you will have an over-exposed picture, if too little light, and it will be under-exposed. The shutter is one of the three ways one can control exposure. the other two are “aperture” – covered in the next lesson – and “ISO”, covered in lesson 110.
This lesson will focus on how a shutter works, and how it influences your photo.
Getting off green mode.
You need to get off green mode. Many camera control dials have many settings. Most of these settings are pure hogwash and gimmickry. Yes, these settings have a function, but if your goal is to improve your skills, you need to move off these “auto” functions and start doing things by yourself. These functions are just different settings where the camera thinks for you. I trust that you are here because you do not want a machine to think for you, but that you tell the machine what to do. These settings will take the average reading for each of the average settings and give you an average picture. I hope you are reading this because you do not want to take average pictures…
Above is the control dial of a Nikon D5000. As you can see, it has many settings. I honestly do not know why. To the amateur, they are confusing, to the pro, they are unnecessary. The only area of the dial we are interested in, is the white part, the P-S-A-M part. But only three of those, we are not interested in “P” mode. “P” stands for “Program” mode and is just a fancy word for “fully automatic”. I have no idea what the difference is between the “P” mode and “Auto” mode, and I do not have any desire to find out. As both settings lets the camera think on your behalf, I don’t want that to happen; I want to tell the camera what to do.
(Most cameras, irrespective of brand have these dials/settings in some form or another. The naming conventions and/or icons may not be the same, but they do the exact same thing. For instance, “S” on Nikon cameras, is the same thing as “Tv” on Canon cameras. On Nikon it stands for “Shutter”, on Canon, it stands for “Time Variation” – but they perform exactly the same function. To-MAY-to to-MAH-to). The other icons vary from camera to camera and are all just pre-set adjustments for the camera to do the thinking for you. Professional level cameras do not have these other icons, they just have the P-S-A-M options.
Throughout this course, and hopefully through your career as a photographer, we will concentrate on the S, A and M modes of the camera. A stands for “Aperture”, and we will cover that in the next lesson, and “M” is for fully manual, which we will look at in lesson 111 – The Holy Trinity.
So, let us begin – let us take the dial, move it off green mode, and move it onto “S” (or Tv) mode. Congratulations – this is your first step in getting yourself onto a new path of photography.
What does it do?
When you set your camera to shutter priority, it means that YOU tell the camera what the shutter speed will be. The camera will then automatically calculate the ideal aperture opening for your chosen shutter in the given light conditions and ISO. In effect “S” – or “Tv” – is a semi-automatic mode. This is great for now. (If you do not know what “ideal aperture” or “ISO” means, don’t worry, we will get there – this is one of those “learning to read” moments!)
Semi-automatic ain’t a bad thing!
Being on a semi-automatic mode is not a bad place to be. I shoot very little of my out-of-studio work in one of the semi-auto modes. (All my studio work is in full manual). The reason I do not shoot that many full manual shots outside the studio, is because the camera can think faster than I can. I know what I want to capture, and I set the appropriate shutter or aperture value for it, and let the machine set the other one. I only go into full manual mode when I want to override the default calculations of the camera – if I want to over or under expose my photo.
What does it look like?
On your camera control, you may find a range of shutter speeds that looks like this:
(I made this drawing as a generic sample. Different cameras have different ways of doing things, and I did not want to use a camera-specific button to avoid confusion. Or, you may not find a dial at all – most dSLRs these days have electronic shutter controls.)
The first thing you will notice is that some numbers are a different colour than others. The white numbers are indication in fractions of a second – 1/4000th of a second, 1/2000th of a second, and so on, until we reach half a second. When we reach 1, and then go back to 2 and 4, the colours change. This is now we are not talking in fractions of a second, but in full seconds. Thus white-2 is half a second, while orange-2 is a full two seconds.
The second thing you may notice is that “60” is also orange. Why is this? Cameras usually have a flash-sync-speed, the speed at which your camera flash will sync with your shutter. This varies from model to model, but you will usually find the shutter that syncs with your flash a different colour, and this is the recommended setting for using your flash. However, flash photography goes beyond the scope of this book.
The last thing you may notice is that the last number is not a number, but “B”. That “B” stands for “Bulb” and is a throwback to the ancient days of photography. What this means is that as long as you keep your finger on the button, the shutter stays open. Many cameras have done away with the “B” function, but know it might be there.
And yes, the dreaded “AUTO” function is also there. Forget about it, we’re now telling the camera what to do, we’re not going to allow it to make decisions for us!
Turn the knob until you get to your desired shutter speed, and the camera will expose for that speed. If you are shooting on “S” or “Tv” mode, the camera will automatically set the aperture for you.
(If you are not sure about why the numbers are sequenced the way they are, be sure to read the primer on this lesson – “Double and half” in lesson 104)
What does it do?
Shutter speed is, obviously, the amount of time your shutter stays open. The longer it stays open, the more time goes by, and the main implication of this, is movement.
One criterion for a good photo – if not a great photo – is sharpness. A photo needs to be sharp. there are exceptions (See my philosophical lesson on “know the rules, and break them like an artist” in lesson 404), but for our purposes – a photo needs to be sharp – bottom line. Movement, either of the camera, or of the subject, will cause blur. When a photo is blurry, it’s probably not usable.
Thus, you generally would want a shutter speed as fast as you can go. The faster the shutter, the more likely it is that you will freeze motion and get a sharp image.
A good baseline speed to work from is one sixtieth of a second. 1/60 – or, just “60” – as the setting on your camera. This means that the sensor on your camera will be open for exactly one sixtieth of a second. This is also the generally accepted slowest hand-held speed. If you shoot slower than 60, for instance at 30, your heartbeat will shake the camera. Yes, literally. And yes, it’s that sensitive. All that needs to happen for a photo to go from “sharp” to “blurry” is a one-pixel shake. Professional rifle shooters actually train to pull the trigger between heartbeats! So, rule of thumb, if you need to, or want to, go slower than 60, use a tripod. (Lesson 210).
“Slow” and “fast” are relative terms. Is Usain Bolt slow or fast? Compared with what? A train or a pudding? So, for the purposes of this lesson, everything faster than 60 we will call “fast” and anything slower than 60, “slow”. This is not a scientifically delineated measurement, but is a good baseline to work from, from this point forward. If you have sharp light, such as direct sunlight, or if freezing the action is essential to your shot (Such as sports photography), you will use a faster shutter speed – usually around 1000. If you are in low light conditions (such as shooting a wedding in a church), or you need to show movement in your image, you will use a slower shutter speed, around the 30 or 15 mark
I use shutter priority in my camera when motion – or the lack of it – is essential to my shoot. I once had to shoot for a big multinational pet food company an image of a dog jumping over a fence. To freeze the dog in mid-jump was mission critical, and as such, I put my shutter speed as fast as lighting conditions would allow. On the opposite side of the spectrum, shooting moving water – such as a waterfall or ocean waves – setting up on a tripod and giving the movement time to register on the sensor, gives a wonderful, silky, serene feeling to a photograph. In fact, many people I know specialise in slow-shutter photography, and utilise expensive specialist equipment just to open up the shutter for as long as possible.
Fast or slow, it does not matter, neither one is “better” than the other – it all depends on what you want to shoot, and how you want to portray it.
How does it work?
Modern day DSLR cameras have a two-curtain shutter system, a front curtain and a rear curtain. These curtains open in a synchronised way to expose the photographic medium. The time it takes for these curtains opens and exposes the medium to the light, is the “shutter speed”.
The image below illustrates how the shutter operation works – it’s highly simplified and stylised, but it gives an accurate depiction as to how a shutter basically works. The black part is the camera body. In front of it, the silver part, the sensor. The yellow and blue bits represent the shutter itself, with the yellow part the rear curtain, and the blue bit, the front curtain.
- Image 1: The shutter in “closed” position. The default state.
- Image 2: When you click the shutter-release button, the rear curtain slides up.
- Image 3: The front curtain slides down, exposing the sensor to the light.
- Image 4: The rear curtain falls back down
- Image 5: The front curtain pops back up, and we’re back at the default position.
This sequence can happen as fast as one eight-thousandth of a second. That’s a couple of thousand times faster than you can blink. Or it can take as long as… well, there is not really an upper limit.
To illustrate further how the shutter works, I’ve expanded the sequence above into a more detailed process. (I was having fun drawing pictures, okay!?)
- Image 1: The shutter at its default position.
- Image 2: Rear curtain up.
- Image 3: Front curtain drops – the image starts being exposed to the sensor
- Images 4, 5 & 6: As the front curtain drops, the rear curtain falls, blocking light from the sensor. As these two curtains fall in synch with each other, a uniform gap is always between them, allowing the light to hit the sensor evenly.
- Image 7: Rear curtain completely closed, front curtain completely open, we now have the image completely captured on our sensor.
- Image 8: The front curtain pops back up – the image is transferred from the sensor to the memory card, and we are ready to shoot again.
Try to photograph running water – it can be a beautiful serene setting in a nature reserve or it can be the kitchen tap – the principle is the same. Set your camera to Shutter priority, and start at one sixtieth of a second. Look at the result and then move the shutter up and down in both directions – look at how the longer shutter speed influences the look of the photo. I recommend that you stabilise your camera for this exercise to keep it in the same position and to avoid camera shake. If you do not have a tripod, try resting your camera on something, but a steady camera is essential for this exercise. Going hand-held will in all likelihood not give you the required results.
Remember, we’re doing an exercise in principles here, we’re not going for Pulitzer-Prize winning photos just yet!
Header model: Raven Rose – Yes, again!