Follow Low_ISO on Twitter for blog update notifications What contributes to focus? There are several things that do, and most of them can be improved with technique. Note that these techniques become even more important as you zoom into a subject. If you are shooting telephoto over 200mm, every little movement is going to be amplified.
1. Camera Shake
This is the one most people associate with blurry images. Even if your subject is static, your image isn't going to be sharp if you are bouncing when you take the shot. The obvious solution to get rid of shake is to use a tripod or set the camera on something, but I am going to focus on hand-held here. Even pressing the shutter button can move the camera a bit. So how can you steady those hands?
- Hold your breath. Not until you turn purple, but just while you take the shot. When we breathe, our body naturally moves. It may seem minor but it does have an effect.
- Use your eyebrow. Cameras aren't light. An average DSLR with a lens on it is going to weigh a couple pounds. If you have nothing to lean on to stabilize your camera, use your face! It's easy to see the effect of doing this if you have a zoom or telephoto lens. Zoom all the way in on a subject and look through your viewfinder. Try to hold the central focus square completely still on your subject. You'll find that it's virtually impossible. Now, jam the viewfinder up against your eyebrow and hold it there. You don't have to push hard enough to leave a mark, just even pressure. Now try to hold the square over your subject. You'll find it's much easier!
- Take a wider stance. When shooting, don't have your feet together, spread them out a bit. Your body is much more stable when you take a wider stance. Brace yourself against the ground, you'll find that it's easier to hold still.
2. Depth of Field
Choosing the right aperture has a major effect on blur and focus. The smaller this value, the less margin for error you are going to have when you focus. If you are shooting at f/8, you have a bit of cushion. Even without perfect focus most things in the frame are going to be sharp. At f/4, you have to be much more precise, and once you get in the 2's, your depth of field will become very thin and you need to be perfect. Provided you have sufficient light and aren't shooting wide open for effect, keeping the aperture above f/5.6 or so will make it easier to keep things in focus.
3. Shutter Speed.
We know that when shooting moving subjects a fast shutter speed is needed to stop action, but what about static subjects? Well, you still need enough speed to help minimize camera movement. As a rule of thumb, aim for 1/125 at a minimum. As your technique improves, you'll find that this value will get smaller. With solid technique, most shooters can get shake-free images down to 1/60, or even smaller. This is especially important in low light conditions. You may be shooting wide open indoors and notice your shutter dropping below 1/60. Once you get to this point, you are reaching the limits and should consider either using flash or finding something to set the camera on.
4. Autofocus
Every modern camera has autofocus. This is a good thing, right? We can just snap away without a care! Unfortunately, no autofocus system is perfect, and even high-end cameras have problems in lower light conditions. The best way to make sure your subject is in focus is to do it manually. What?!? Focus manually? But it's so slow! Yes, focus manually. I use manual focus on over 90% of my shots, and I rarely get one out of focus.
The reason autofocus can fail sometimes is because they are complex systems. Many SLR cameras have 7 or 8 focus points in the viewfinder, and another 10+ points that are "hidden" that the camera uses to evaluate focus. This is usually very accurate, but it can be fooled. Your camera 'sees' the scene and evaluates it, but it does not truly know what you are trying to achieve with the shot. It doesn't know if you are focusing on a person's eyes or nose, for example. For this reason, manual focus will always be the most precise. While I would never dream of shooting action without autofocus, I almost always shoot static subjects this way. With live-view cameras, this is even more accurate. You can zoom in on the LCD screen and make sure everything is sharp before you push that shutter.
I'm going to be honest with you, manual focusing is not an easy thing at first. Like learning to ride a bike, it takes practice. After a short while, though, it becomes almost automatic as you get used to your lenses. The next time you go out shooting, I challenge you to turn off that autofocus and see what you can do. After you get used to it, you will be pleasantly surprised.
5. Lens Quality
OK, this one isn't a technique, but it bears mentioning here. If you are a pixel peeper who is going for the absolute sharpest images, you are going to want to good some good glass. The lenses that ship with most cameras are quite good, but you are going to be hard pressed to produce razor sharp images with them. Lets say you have two lenses. A standard 35mm prime that cost you around $300 and a high-end 35mm prime that set you back $1200. Put them both on a tripod, manually focus to minimize error, and take some shots. When you compare them, you are going to find that with all things being equal, the expensive lens is usually going to be sharper. If the focus is the same, why is this so?
Without going into a lecture on optics, other things contribute to the sharpness of an image besides focus. If you are shooting higher contrast scenes (like a darker subject against a bright sky), the edges of objects sometimes have a colored halo on them (called chromatic aberration). This happens because different wavelengths of light have different properties, and it's difficult for a lens to focus all these different colors precisely. Having color on an edge can make something look 'soft' by reducing the contrast, it's almost like a haze around the object. More expensive lenses have special coatings or are made up of different elements to minimize this, which produce sharper images.
In addition, the more expensive lenses usually are precision manufactured in a way that increases microcontrast. The better the microcontrast a lens has, the more detail and sharpness it usually achieves. A very high-quality lens will be able to reproduce the difference between two very close shades of gray, whereas a lower quality lens will not. Lenses from Leica and Zeiss are legendary in this regard, and have incredible contrast. This comes at a premium cost, however, and the price tags aren't for the feint of heart.
Both of these things attribute to the sharpness of an image, and quality glass is better at handling both of them. Great glass isn't always needed, however. I can, and do, get some fantastic images with lenses that cost me under $150. With nice even lighting and good conditions, my more affordable lenses look nearly as good as my expensive ones for everyday scenes. When I want to reproduce great colors in a very detailed scene, however, I reach for the quality glass every time.
A final note on this. Running out and spending thousands on glass is not going to magically make your images better. A solid technique is much more important to master first. As you get better at photography, you will know when you get to the point where your gear is limiting you, and when it's time to consider looking for some better optics or a body with more features.
So, a quick recap on getting sharper images:
1. Check aperture and shutter speed, make sure they are favorable for the conditions.
2. Make sure the subject is in focus, manual focus being the preferred method.
3. Take a sturdy stance, brace the camera, pause breathing, then shoot.
This will help you produce sharper images. Happy shooting!
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