Underwater Programming Laboratories


Focus

Focusing is not always as simple as point the camera and shoot. Depending on how you are composing the scene, lighting, or even your subject may lead to difficulties getting that picture sharp.

There are basically two types of focusing systems available. You can get cameras that use a range finding system or cameras that focus though the lens. Range finding systems use two lenses and superimpose the image in the viewfinder. When looking through the viewfinder you will see two overlapped images of the same scene. While turning the focus one of the images will shift over the other. What ever lines up in the viewfinder is in focus. A very simple system to use and not prone to many problems. The only draw back is all focusing must be done manually.

The second system, through the lens focusing, is a bit more complicated. If you are focusing manually while looking through the lens via the viewfinder, you are relying on the calibration of the viewfinder. If it is off just slightly you will not be focusing on what you think you are focusing on. The easiest way to focus through the lens is by letting the auto focus system in the camera do the work for you.

If you choose to let the auto focus do the work then there are some things you need to know and how to work with it. Most auto focusing systems work by trying to focus on a sharp contrast. In simple terms, a sensor inside the camera is examining what the camera is pointing at, changes the focus to see if it becomes sharper than it is blurry, and settles on the sharpest it can make it. This type of focusing has a few limitations.

Auto focusing systems are limited by the area of the scene it is examining. Generally most look at the centre of the scene. Some have the ability to change where it is looking and can become confusing for the beginner. You man not always want the subject you are focussing on in the center of the scene where the auto focus is looking. The way around this is to use the two stage stutter release built into just about every camera that has auto focus. When you press the shutter release half way down the auto focus is engaged and the camera will attempt to focus. Once it has focused, it will hold that focus until you release the stutter release. If you are taking a picture of a subject that is to the right of the center of the scene, point the camera at the subject, press the shutter release half way down, and wait for the camera to focus. Most cameras will beep or show a little light when it has focused. Now move the camera to left, right, up, or down to where you originally wanted to point the camera. Press the shutter release the rest of the way down to take the picture. Be careful not to move forward or backward after the camera has focused. If you do, the distance from your subject will change and the focus will no longer be as sharp. If you think you have moved, just release the shutter release and start again. I find when I am squatting down, I tend to rock forward and back a bit.

Focus on the subject and then re-aim the camera Auto focus can be handy when you don't have to focus manually

Another limitiation is auto focus requires enough light for the sensor to see what the camera is pointing at and detect the sharpness. In low light conditions, it will have problems detecting the sharpness as it tries to focus and will fail. Check to see if your camera has a focus assist lamp. If you have taken pictures in low light and seen a light come on lighting the subject then you have one. The camera will detect the low light and turn the lamp on while it is trying to focus. This will help the sensor try do detect a sharp contrast point and focus on it. While photographing animals you may want to turn this off. For some reason they don't seem to like it very much.

Sometimes the subject has no sharp contrast points for the sensor to see. A few examples would be snow or a fuzzy black dog. If you have ever tried to focus on a fuzzy black dog, you will know what I mean. Auto focusing systems have problems with many solid colour surfaces or dark surfaces that absorb light. If you find yourself in this situation, you may still be able to use the auto focus. Look for something else the same distance away. Point the camera at that, press the stutter release half way down to focus. You can then move the camera back to take the picture.

Tripods keep the camera still when shooting in low light Any movements while subjects are extremely close with greatly affect focus

If for some reason you just can't get the auto focus to lock and your camera has a manual focus you will have to use the manual focus. Take some time to familiarize yourself with turning the auto focus on and off with out having to fumble too much with the camera. Also take some time to practice using manual focus to become comfortable with it. It is a good thing to be able to do to get that shot if the auto focus just won't behave.

Tips

  • Understanding depth of field will also help understand how to get better focusing while taking pictures.
  • Using a tripod or some other form of support will help get shaper pictures by reducing camera shake introduced into the camera by your hands.
  • Always remember to gently squeeze the shutter release down. Any jerky or sudden movements made by your hands will translate into the camera.
  • Pressing too hard or too quickly on the shutter release can cause a few heads to be chopped off as you unknowingly push the whole camera down.
  • If using a tripod of setting the camera down on a surface, consider using a remote or shutter timer to keep your hands off the camera when the shutter fires.
  • Make sure the viewfinder on your camera is adjusted correctly to match your eye.
  • A recommended way to hand hold a camera is to stand with your feet at shoulder distance apart. With both hands on the camera keeping your elbows down to your side to help stabilize your arms and hands.

Now go out and have some fun with your camera.

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