Your camera has several markings on them. The main shooting dial on your camera has the markings P, A, S, M, etc. There are several other markings on the camera and lens body.
The S marking is for Shutter Priority. On some camera systems, it’s marked as Tv for Time Value, but they’re all the same thing.
Shutter priority is the setting on your camera that allows you to manually control the shutter speed and let the camera automatically adjust the aperture and sometimes ISO using the built-in camera metering.
Switching to this mode means you’re switched to Shutter Priority mode.
For clarity in this discussion, I will continue to use the letter S to signify it.
What purpose does shutter speed serve?
The purpose of shutter speed is to control the amount of light that enters the lens. Once you better understand shutter speed and aperture, you will realize that they both do the same thing. They both control the amount of light that enters the camera.
However, while the aperture controls the size of the lens’ hole (opening) to let more (or less) light enter the camera, shutter speed controls the extent or the length of time for which the shutter curtains remain open.
So, they tend to do the same thing, but the mechanism is different. Of course, they control other aspects as well, and we’ll learn about those aspects later.
Working with Shutter priority mode
Once you set the main shooting dial to S mode, you will be able to control the Shutter Speed of your camera. As you turn the command dial, you realize that the shutter speed settings are changing. You can now select a shutter speed as per your choice.
Depending on your preference, you can use a fast shutter speed like 1/1000 sec or a very slow shutter speed like 1 sec.
However, changing the shutter speed comes at a price.
Shutter speed and Aperture value have an inverse relationship. In other words, if you change the shutter speed, you’ve to change the aperture value as well. Let’s take an example to demonstrate this.
Shutter speed changes in stops just like the aperture does. One-stop signifies halving or doubling the amount of light that gets through.
Let’s say that your shutter speed is 1/100 sec at aperture f/4.
Now, let’s say you want to increase the shutter speed and choose a faster shutter speed. Let’s say you set the shutter speed to 1/200 sec. What you did was push the shutter speed by one “stop.” Now, the amount of light entering the camera will be exactly half of what you would have received at 1/100 sec.
This is because the aperture value and the ISO remain the same as before.
Now comes the exciting part.
As I said, changing one of the values between Aperture and Shutter speed will warrant a change in the value of the other. Otherwise, your exposure will be botched.
To compensate for the increase in shutter speed, your camera will automatically change the aperture when in shutter priority mode.
Increasing the shutter speed resulted in less light entering the camera. How much less? Exactly one stop. To compensate for that light loss, it will open up the aperture one stop.
The initial aperture was f/4, and now the shutter speed has gone up by one stop, so we have to compensate by opening up the aperture by one stop. So, our new aperture should be f/2.8.
In shutter priority mode, the camera will also adjust the aperture to react to changing light conditions of whatever you are pointing the camera at. So in the above example, if you kept the shutter speed the same, but pointed your camera at something darker, it would also open up the aperture to let more light in.
Aperture values are always expressed as a fraction, like this – f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, and so on. If you go up the chart, the lens’s aperture becomes smaller. Yes, it’s a bit confusing because higher numbers mean a smaller aperture, but you’ll get the hang of it quickly.
Essentially, shutter priority mode does the work for you by using its metering system to determine what the best aperture is for the shutter speed that you chose.
What if shutter priority mode gives me a bad exposure?
The inherent weakness of any of the “auto” modes is that you are dependent on the camera’s metering system to choose the right exposure for you and this isn’t always going to give you the best result.
The good news is that you can take some more control with the exposure compensation dial.
Any camera that has a shutter priority mode will allow you to adjust exposure compensation in some way, usually in the form of a dial on the front or back of the camera.
Exposure compensation is simply a way to tell your camera that you want the image either brighter or darker than what the camera’s metering has decided is correct.
This allows you to use a mode like “shutter priority” and still take control over what the camera s doing.
Most cameras allow you to adjust exposure compensation about 3 stops brighter or darker.
Creative ways to use shutter priority mode
I will discuss a few creative ways to use the shutter priority mode to conclude this discussion.
A majority of the creative ways of using the shutter priority mode is to drag the shutter or use a long shutter speed.
Let’s say that you want to capture images of a fireworks display. The best approach is setting up your camera on a tripod, switching off image stabilization, setting your camera to Shutter priority mode, and using a long exposure of 1 sec or more to capture the images.
This simple trick can capture light trails, light painting, and other low light genres though the shutter speed will vary based on the exposure time required.
You can use a slow shutter speed during the daytime as well. Intrigued? You will need a Neutral Density (ND) filter for that. Neutral density filters come in different strengths of light stopping power. A 4-stops ND filter will allow you to drag the shutter by four stops: brighter the conditions and longer the shutter speed required, the more light stopping power you need.
Should you use shutter priority mode?
My short answer is “rarely.”
As you can see with using exposure compensation, you’ll usually end up making adjustments anyway to fine-tune your exposure. It’s not often that the camera gets it perfectly right.
So at that point…why even bother with using one of these “auto” modes?
It can actually be far easier to put the camera in manual mode, set your shutter speed, and just adjust the aperture yourself rather than using exposure compensation.
One exception where I’ll admit shutter priority mode can be helpful is when you are in a situation with fast-changing light conditions.
For example, you may be shooting a sporting event outside where the sun is coming in and out of the clouds. Using shutter priority to make sure you have a fast enough shutter speed and letting the camera adjust the aperture based on the light can be helpful.
But those situations are rare. So I am not a big fan of the priority modes. Try getting used to using your camera in manual mode, you may be surprised that it’s actually easier.
