What makes an image sharp?
A number of different factors affect sharpness, and they’re all important if you want to understand how to take perfectly sharp images straight from the camera. Out of all of these, which do you think affects sharpness?
- The aperture setting.
- How far away you are from your subject.
- How still you can hold your camera.
- The shutter speed setting.
- The ISO speed setting.
- How far away the background is from your subject.
- The amount of light available in the scene.
- The type of lens you’re using.
Naturally, it’s a trick question. All of these affect the sharpness of the pictures you take. They are all relevant. That’s the sort of perspective we need to take on sharpness, and it’s the reason why sharpness is considered a sort of mythical “holy grail” of photography. Those who are seasoned and experienced with the art seem to know how to pull sharpness out of thin air.
There’s a second aspect to sharpness that can easily go unnoticed if you don’t address it right away. Before you take any picture, ask yourself which parts of your photo should be the sharpest and which should be a little blurry or completely blurred out. Sharp for sharp’s sake doesn’t a good photo make. You need to make a creative decision and apply sharpness only where it’s needed.
Case in point, a portrait. Unless you’ve got a perfectly clean background behind your subject, you normally won’t want the background to be sharp. You’ll actually want it to be a little blurry so as to draw less attention to itself and more attention to the person in the photograph. That’s what I mean by making a creative decision. Before you decide to make an image more sharp, you need to pick the area you want sharp.
A breakdown of what affects sharpness
Chances are you already knew that. I just hate to leave the important stuff out. I think that if we’re going to look at sharpness from the camera’s side of the equation, we really ought to break down everything that can contribute to or detract from the sharpness of your images. So, without further ado, here’s the giant checklist.
The aperture setting
Aperture affects sharpness by making the light entering your camera more or less organized (that’s a simplification, but it will do for our purposes). A very small aperture does a better job of organizing the light, resulting in a sharper image on your camera’s sensor. A very wide aperture, on the other hand, leaves you with a more disorganized kind of light. Whatever isn’t exactly in focus will appear blurry or out of focus.
How far away you are from your subject
You probably weren’t aware of this, but the closer you get to your subject, the less sharp the image of your whole subject becomes. That’s why it’s very common to see macro images of insects where only a small part of the insect is sharp while the rest of the scene remains out of focus. Contrast this with giant sweeping landscapes the are almost entirely in focus. Part of their sharpness results from focusing on the furthest point in the background and making it the main subject.
For example, with such a short distance from the bee in the image to the right, depth of field decreases and only the insect remains sharp.
How still you hold your camera
If you’re shaking while you take the picture, and you’re using a slow shutter speed (even a fast one sometimes), it will adversely affect the sharpness of the resulting image. You have two options if you want to correct this. You can either get a tripod, or you can learn some breathing and camera holding techniques for optimal results. In general, exhale as you take a picture, and hold your camera as close to your body as possible.
The shutter speed setting
Shutter speed only affects sharpness if you’re holding the camera as you take the picture. If you’re set up on a tripod, you can ignore this. Here’s the basic rundown. As you increase your shutter speed, your image becomes less susceptible to the effects of you shaking your camera (even if it’s slight) while pressing the shutter button. To increase sharpness, increase the shutter speed.
The ISO speed setting
A handy tool for getting more out of a low-light situation. Such handiness, however, must come at a cost. Whenever you increase the ISO speed, your image becomes slightly more grainy and a little less sharp. That’s why some camera makers have gone so far as to create new ISO speed settings like 50 (half of the lowest value), which have nothing to do with the film standard ISO speed evolved from. Photographers want more sharpness, and this is one way to give it to them.
How far away the background is from your subject
A far away mountaintop will be less sharp than the Swedish cottage your friend is standing in front of. That’s just the way light works. There’s more atmosphere for the light to pass through the further away an object is, so the light coming through the lens is a lot more disorganized. Couple that with a wide aperture, and you can see what happens. You see your friend’s face, and you can make out some of the cottage. But forget about the mountain. It’s a mess of hexagon-shaped light (a.k.a. a bokeh).
The amount of light available in the scene
I’ll admit that this is only tangentially relevant to sharpness. You don’t necessarily need a lot of ambient light to make a sharp image. But man, it sure does help. When you have more light, you can use a smaller aperture or a faster shutter speed. Those two, as we’ve said earlier, will definitely give you a sharper image.
The type of lens you’re using
Have a look through some old photos, and you’ll notice something right away. They’re a lot less sharp than the images we’re used to in today’s day and age. Why is that? Simply put, lenses weren’t as well constructed as they are today. They didn’t do as good of a job of organizing the light into a straight path. As a result, early images have a kind of dreamy soft-focus sort of look. Most of it can be attributed to the lens itself.
What about high-end lenses and their off brand counterparts? Is there a real difference there? It would be foolish to say there isn’t. A more expensive lens will give you a somewhat sharper image, but here’s the thing. All of the other factors we’ve mentioned influence the sharpness of your image a lot more than the lens you choose. If anything, a difference in the lens (especially by today’s standards) has only a small effect.
In other words, nothing is a replacement for good old fashioned technique. It doesn’t really matter what camera you have. Any camera is pretty much as good as another when it comes to sharpness. The “trick” is to grab one, get out there, and take as many pictures as you can. Your images will become sharper as you evolve into a better photographer.