The Exposure Trinity - The 3 Components of Exposure

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What is Vibration Reduction?

Nikon's Vibration Reduction system (or Image Stabilization from Canon) helps us take sharper pictures at slower shutter speeds. It's too complicated to understand or explain how it works, so just think of it as magic (see the magic here.) It's a part of lenses that are labeled with VR (Nikon) or IS (Canon) that makes photographing easier.

To understand what it does, you must first understand the problem of camera-shake. VR compensates for camera-shake allowing us to take pictures at slower shutter speeds than we would be able to unassisted. Look at what it does:

Both of these images are shown at 100% magnification, so you are seeing them pixel for pixel. Both come from much larger photographs that were each shot at 200mm with Nikon's 55-200 VR lens at a shutter speed of 1/30. The one on the left has VR turned off and the one on the right has it turned on. You can see the affects of my shaky hands on the left and the affect of VR on the right.

What does this mean?

If you remember that your options for choosing a shutter speed can be limited by camera-shake, then the benefit of VR is probably obvious. Using VR allows us to use shutter speeds that are slower without paying the price of having blurry pictures. Using the equation I gave in this post, we would expect to need a shutter speed of 1/300 to produce a sharp image at 200mm. But at 1/30 I got a decently sharp image. That's a big advantage.

How to Choose a Shutter Speed Part Two

As I mentioned in Part One, one of the main factors that should influence what shutter speed you choose when photographing is your focal length. (Focal length is the number indicating how far you are zoomed in or out. For example, 18mm or 50mm.) Focal length is important because it affects how much our inability to hold a camera still influences our photographs.

No matter how hard you try, you can't hold your camera completely still. So if your shutter speed is too long (or slow), your entire image will be blurry because of the camera's movement during the picture capturing process. Unlike motion blur caused by subject movement, this type of blur is almost always bad. It looks something like this:

So how fast does our shutter speed have to be to prevent this type of blur? It depends on focal length. The longer your focal length (the more you are zoomed in) the more your lens magnifies or exaggerates your hand movements. You can see this when you zoom into 200mm or so and notice that everything seems wobbly. So the more you zoom in, the faster your shutter speed needs to be.

It is tough to set rules for preventing this kind of blur because different people can hold their cameras more or less still. Also, you may use a shutter speed that would be considered "dangerously slow," and still happen to get a sharp picture. But in general, you can use this equation to determine a safe shutter speed:

1/(focal length x 1.5) = slowest safe shutter speed*

So at 50mm, 1/(50 x 1.5) = 1/75 or faster.

At 200mm, 1/(200 x 1.5) = 1/300 or faster.

At 18mm, 1/(18 x 1.5) = 1/27 or faster.

Remember that this is a starting point, not a law. You may find that you have particularly steady hands and can go a little slower, or that you have shaky hands and need faster shutter speeds. But if you notice motion blur in parts of your image that were not moving, you need a faster shutter speed.

Note, this does not account for Vibration Reduction/Image Stabilization.

* This equation is for DX cameras which include most DSLRs under $2000. For full frame digital cameras, or film cameras the equation would be 1/focal length.

How to Choose a Shutter Speed Part One

(If you haven't read our other posts about shutter speed, click here for some important foundational information.)

When taking control of your camera's exposure, one of the first things to consider is what shutter speeds are "allowable" for the lighting conditions under which you are photographing. The answer to this depends on two main factors:

1. The speed at which your subject is moving
2. The focal length at which you are photographing

We'll tackle the first issue today . . .

If you want your subject to appear still, then your shutter speed must be fast enough to "freeze" any motion. Here are a few bench marks to keep in mind.

• If you are photographing people who are trying to stand still (and doing a good job of it) then 1/60 is a safe shutter speed. If you need to go slower, you can fire off a few pictures in a row and maybe get a sharp one, but the more people in the picture, the more likely someone will be a bit blurry.
• If your kids are walking around, playing, or running around outside, you want to be up to 1/125 or even 1/250 to be safe.
• If you are taking pictures of kids swinging a bat or driving a race car, you'll need a shutter speed of 1/500 or faster.
• If you are photographing a rock that isn't moving, any speed is safe as far as subject movement, but then photographer movement comes into play.

Keep in mind these are guidelines. You can always try something slower if you want, or you may need something faster than what I've suggested. Just remember to think about this when you are controlling your shutter speed.

Also keep in mind that these are guidelines for freezing the motion. If your subject is moving, you need to consider whether or not you want it to appear still and sharp or you want to allow for some motion blur. Sometimes motion blur is a good thing, so don't get locked into thinking you need sharp, motion-free images.

Using Slow Shutter Speed Creatively

When you slow down your shutter speed, your sensor records what you aim your camera at for a longer period of time. This means that if something is moving, the movement will be recorded. The effect that we see is called motion blur or implied motion.

In the picture of the waterfall above, my shutter speed was 1/3 of a second. Over the course of that 1/3 second, the water was moving and the rocks were not. Therefore we see the implied motion of the water in the blurry streaks, but the rocks are crisp and clear.

In the picture below, I set my shutter speed to 1/60 of a second to capture the motion and excitement of Belle as she emerged from her hiding place behind the curtain. Notice again, the things which are not moving are sharp, while the things that are moving appear blurry.

This technique can be used in numerous ways. Try slowing your shutter speed down while you are photographing moving things and see what you get. As you experiment with this, you might discover your a need for a tripod. I'll discuss this soon.

How to Control Shutter Speed

Shutter speed is one of two factors that determine how much light your camera's sensor is exposed to when you take a picture (exposure.) Consequently, shutter speed is one of the most important things to understand if you want to venture out of "green box" mode.

Controlling your shutter speed gives you more control over exposure and more control over creativity. The simplest way to begin experimenting with shutter speed is to put your camera in "shutter-priority" mode. To accomplish this, rotate your camera's control dial (indicated below) to "S" if you have a nikon camera like the D40 or "Tv" if you have a canon camera.

In shutter priority mode, winding the command dial (indicated below) will change your shutter speed and your camera will do the rest of the work to produce a correct exposure. As you peer through your viewfinder, you will see a number changing as you wind. That number indicates your shutter speed (it's not the number with the "f" in front of it, but the other one.) The number indicates the reciprocal of your shutter speed in terms of seconds. In other words, if you see a 60, then your shutter speed is 1/60th of a second.

There's lots more to say about shutter speed, but that's enough for one day. Try experimenting with it and see what happens. More on this tomorrow.

What is Shutter Speed?

Here's a video explaining what shutter speed is: