Like I mentioned last week, exposure is the foundation of photography; it can be difficult to master, but having a basic understanding of how it works will help you improve your photo game by leaps and bounds. Learning how to operate your camera in manual mode will help you to take advantage of everything it has to offer, but you’re going to have to figure some of that out on your own since every camera is different. It’s unlikely that you’re using the same model that I am, so I probably can’t advise you on the technical aspects of your digital camera.
What I can do is show you how controlling the elements that make up exposure will affect your photography. We’re starting with shutter speed.
First, the technical details. The sensor in a digital camera acts a bit like film in an analog camera. It captures the light that comes through your camera’s lens and creates the image that you see. I’m not going to get that technical, so here is a helpful article if you want to know exactly how a sensor works. The shutter is like a little curtain inside your camera that opens and closes to expose the sensor to light. Your shutter speed determines how long the curtain stays open. It’s usually measured in fractions of a second.
All three elements of exposure have two features. Shutter speed determines how long your sensor is exposed to light, which will make your photo brighter or darker depending on your surroundings. The longer the shutter is open (i.e., the slower your shutter speed), the brighter your picture will be. It also determines how motion is captured in an image. For example, a high shutter speed will freeze birds in flight while a low shutter speed can give an artistic blur to flowing water.
When I’m getting ready to set my shutter speed, the first thing I try to consider is whether something is moving in my shot and how I want to capture that motion. My next concern is the amount of light that is available to me.
If nothing is moving, I use shutter speed and ISO to control the amount of light in the image, and aperture to determine what parts of the picture will be in focus. We’ll discuss using aperture this way in more detail next week, so for now let’s concentrate on motion. You’re going to want to practice this ahead of time if you have any big shoots planned. Don’t expect perfection on your first try; it can be a fiddly process to get everything just right.
To freeze motion, you want a high shutter speed. This means that your aperture will need to be a lower f-stop than you might normally use, and your ISO might need to be higher as well. The three elements play off of each other at all times; how you adjust one will affect the other two. There is some math behind this, but I’m saving that for the end of our exposure series; I think it will be easier to explain and understand once we’ve gone over all three elements in detail. For now, here’s a practice scenario for you.
(Note: This is just the way I do things. I’m a kinetic learner–I can read or hear about something until the cows come home, but the lesson isn’t going to stick until I actually start trying to do it. I end up experimenting a lot.)
Let’s say I want to take photos of bees. I don’t, really, I’m terrified of bees, but they’re easy to find and they make a pretty good example for this subject. What I would do is set up my camera with my shutter speed fairly high, then use my aperture to focus on a flower, and take a test shot. It’s usually pretty bright outside when bees are around so I can keep my ISO at its lowest setting, which is 100. If my test shot is too bright, I’ll raise my shutter speed even higher and take another test shot. I’ll continue this until I’m satisfied. Then I’ll try to compose an interesting shot with flowers and bees. If necessary, I’ll make other adjustments and shoot again until I get what I want. Like I said, it’s a fiddly process and I’m still learning.
You can probably get away without using a tripod in this situation because your shutter speed is high and camera shake won’t be as big of a deal. It’s when you get into low shutter speeds, let’s say slower than about 1/60 of a second, that you will probably want to use a tripod to get the best possible shot.
Now let’s look at low shutter speeds. Although you’re usually shooting in fractions of a second, a slow shutter speed can be full seconds depending on what you want to capture. Some cameras even have what’s called B or bulb mode, which keeps the shutter open for as long as you hold the button down. When your shutter speed is low, your sensor is exposed to light for a longer period of time. This means your aperture needs to be a higher f-stop and your ISO might need to be higher as well. It can be hard to get a long exposure shot on a sunny day without overexposure; for best results, try shooting on overcast days or even at night when you want to use a low shutter speed. Here’s something fun to try at night.
Set up near a fairly busy road. Obviously you don’t want to be so close that cars will hit you. A rooftop or an overpass that has a sidewalk will be ideal. You want a low shutter speed, start out around 2 or 3 seconds. Use your aperture to focus on any stationary things or objects of interest in the area. Your ISO should be low, around 100, because this is all about the light and you want it to be as free from noise as possible. Wait until a car is coming by, then take the photo. Pretty cool, right?
You’ll definitely need a tripod for this sort of shooting. A shutter remote helps as well because then you don’t even have to touch the camera and risk shaking it. You can get some interesting effects if you set a low shutter speed and move the camera deliberately, though, so feel free to play around and see what happens.
There is some math involved in the relationship between your shutter speed and the amount of light that reaches your sensor, but I decided to keep things simple since this is supposed to be a basics post. I wanted to cover this somewhat briefly, and I think this is probably enough for one day, don’t you? Leave a comment here or on Facebook if you’d like me to break the numbers down for you, and I’ll be happy to explain! Next Friday we’re talking about aperture, one of my favorite elements of exposure. I’m going to do my best to have some fun pictures to share. In the meantime, I hope you’ll like and share this post with your friends! Thanks for reading; see you next week!