Barring certain types of photography where motion (or other) blur are intentional parts of the image, a major goal in photography is to come out with a sharp, in-focus photograph. In order to show you how to take a sharp digital photograph I will identify situations where a less than sharp image may arise and outline what you can do to counter them. Some of these situations include, but are not limited to, low light situations, moving subjects, camera shake, lens specific issues, and camera settings. By tackling some of these issues you will come away better armed with the necessary knowledge to avoid them, ultimately resulting in sharper pictures.
Camera and Lens Specific Issues
Before getting into the specific camera settings for how to take a sharp digital photograph, there are some gear specific considerations which can help you get the sharp photo you desire. For every lens that is out there, there is a specific focal length at which the lens performs the best. Although stopping down a lens to the highest F/number technically brings the maximum amount of the scene into focus, this doesn't mean that the lens is the sharpest there. Most lenses have a spot, generally around the middle of the road (F/8 or thereabouts) where the lens is the sharpest. You can find this spot on your lens by putting it on a tripod, taking pictures of one object through many aperture values, and observing them at 100% on your computer afterwards. Alternatively you can look up your lens' sweet spot on various websites such as SLR Gear. By shooting at this sweet spot whenever practical and possible you maximize your chances of getting a sharp image.
If your camera system's lenses have an image stabilization system integrated (IS for Canon and VR for Nikon), these can greatly improve your handheld shooting. Image stabilization essentially helps to eliminate vibrations caused by camera shake and can help photographers shoot approximately two stops slower than without it. There is some debate to whether or not this can help when the shooter themselves are the cause of the motion. The general consensus as well is that you should turn IS (or VR) off when you are using a tripod in order to maximize sharpness. All in all though, if you are shooting handheld, image stabilization is your friend.
Finally, this should be common sense, but you get what you pay for. One of the simplest ways to maximize the sharpness in your images is to buy the best equipment you can afford. Don't think that the 500mm mirror lens you got off eBay for $100 is going to give you the same quality as a Canon EF 500 mm F/4L USM IS lens.
The first situation we are going to approach is how to take a sharp digital photograph when you are shooting landscapes or other still subjects (such as in product photography). To begin with, I make sure that enough of my scene is in focus through adjusting my aperture. I can't have a sharp digital photograph if my depth of field is too shallow for my subject. Stop down your aperture (increase the F/number) in order to bring more of the scene into focus. To get the sharpest image possible for this kind of subject I always want to use a tripod when shooting. This minimizes any human factors of shake in my shooting process. Finally, put some thought into where you are going to focus your image and make sure that is executed. For product and still photography there is usually a specific object that you want to be in focus so this is fairly straightforward. For landscape photography, you can maximize the amount of your scene which is in focus by calculating the hyperfocal distance and focusing there. If you aren't familiar with the hyperfocal distance, or don't want to calculate it, a good rule of thumb is that you can focus approximately 1/3rd into your scene in order to maximize the sharpness in your scene.
Camera and Subject Motion
One significant source of unsharp images is motion. This can be the motion of the subject that you are photographing or the motion of the camera incurred by shooting handheld (without a tripod). The main way of countering this motion is to use a fast enough shutter speed to halt that motion. You should know what shutter speeds are needed to halt your specific motion. For sports or bird photography this often means using a shutter speed of 1/500th of a second or faster. In order to counter camera shake when shooting handheld, a good starting point is to shoot at one over your focal length or faster. For example, if you are shooting with a 200mm lens, you are going to want to shoot at 1/200th of a second or faster to make sure that camera shake isn't an issue.
You should be conscious that you may have to juggle with your aperture and/or your ISO in order to attain these fast shutter speeds. Increasing the ISO will allow you to shoot with a faster shutter speed, but may introduce noise to your image. Similarly, opening up your aperture will also allow you to use faster shutter speeds, but as seen above, decreases your depth of field. By choosing what "unsharpness" is acceptable and what is not you can use these manual photography basics when figuring out how to take a sharp digital photograph.
Sometimes when photographing moving subjects, your image is unsharp simply because you (or your camera) didn't focus properly on your subject. For sports and animals a good way to prevent this is to use the AI SERVO focusing mode on your digital camera (if available). This adjusts the autofocus automatically for a moving subject while you hold the shutter button part way down. That way you can track your subject and take your picture at the opportune time.
Finally, if the space that you are in and your current equipment load allows it, a tripod or a monopod will give you a little more stability here as well. For these action shots, make sure you choose one that allows you an acceptable range of movement.
Night and Low Light Photography
Low light situations are the trickiest environments for photographers trying to get a sharp photograph if only for the different types of unsharpness that haunt you. If you are photographing a still subject this is less of an issue. Put your camera on a tripod, lower the ISO, adjust the aperture for your desired depth of field and use as long a shutter speed as necessary (but be careful that too long of an exposure can cause noise as well). For situations when you can't use a tripod or there are moving subjects, shutter speed becomes the limiting factor once again. As discussed previously for moving subjects, this now becomes a game of balance between the shutter speed necessary, aperture's depth of field, and noise from high ISO. Essentially you have to pick out what type of unsharpness is acceptable and can be sacrificed to get minimize the other two.
Finally, in order to make sure that your images are sharp, consider using manual focus for low light situations. In night photography or low light situations your camera may search in the darkness to get a fix on the focus and there is more of a chance than usual to end up with a poorly focused image.
When learning how to take a sharp digital photograph, the overall words of wisdom to take away from this article are:
- When at all possible, use a tripod.
- Counteract motion of all kinds by using a fast enough shutter speed.
- Be wary of your depth of field with respect to your desired level of focus.
- Use a low enough ISO to avoid camera noise.
- With respect to focusing, consider using AI SERVO for moving subjects, manual focus in low light, and the hyperfocal distance for landscape photography.
- Know your lens' sweet spot. When possible, use it.
- Buy the best equipment your budget can handle.