28/08/2006

Focusing Control.



Focus - Auto or manual?
Does your camera allow you to switch between manual and autofocus? If not, then this chapter will not apply to you, because we are now going to look at how to get the best results through the use of manual or selective focus control.
With autofocus, you only need to point the camera at a subject, press the shutter button and within an instant, job done! But with a little manual dexterity, you can have the advantage of being much more creative.
As with most cameras, you look through the viewfinder or at your digital screen and place your subject within the focusing grid or lines, which you have displayed in the centre of your viewing range.
But what if you didn't want to have the main subject right bang in the middle of your image, but still portray it as being sharp and clear?
For example, you're taking a portrait of a person standing in front of a glorious sunset and you want to place the person on the right-hand side of the image, so as not to miss out on that great vista.
Firstly, Check out the scene and come to a decision on how you will take the shot. That done, turn the camera toward the person and depress the shutter button halfway, so as to activate focus. When focusing on the person is complete, still holding the button halfway, recompose the scene and press the button. It's a bit like when you copy and paste on the computer.
In another instance, you want to photograph a duck on a pond, but in order to get to the duck, you need to focus through and beyond a clump of reeds in the foreground.
With autofocus, the camera would automatically tend to focus on the reeds because they are in its path, but with manual manipulation, you just turn the focus ring or manual spot focus till you find your target sharp and clear.




With limited depth of field
When shooting a close-up of a flower, no matter what equipment you use, as you get closer to your subject the depth of field you have at your disposal diminishes drastically; so you need to manually select the area of the flower you want to keep in focus. This is where your artistic imagination kicks in because the out-of-focus area is just as important here as the in-focus area and because anything in the scene that is now out of focus, becomes the background and you must treat it as you would any other background. Remembering of course that your background needs as much consideration as the subject itself. Although, in this case, it is out of focus and the emphasis is now on the focused area, you can make use of the out-of-focus elements in the scene to help draw attention to the point of interest or focal point.


Speaking of focusing...
Some people using a digital point and shoot camera these days are encountering the problem that is known as 'shutter-lag'. This relates to the time it takes from when you press the shutter button until the time the camera actually takes the shot. It is generally not a fault with the camera, more with the user.
When you have composed you're shot, just depress the shutter button halfway; this allows the camera's focusing controls to kick in. After which, you can continue to press the button home. Then, simply count to two before moving the camera again. This will ensure you have an 'all-in-focus' shot.
That is, of course, depending on the steadiness of your camera and/or subject.

When do you 'need' to use a tripod to steady your camera?
Most modern cameras today have built-in shake reduction but it is a good idea to find out at what shutter speed this is limited to. If your camera does not permit you that luxury and your shutter speed gets lower than around 1/125 sec, or the light gets dimmer, you will need to think about stabilizing your camera in some way or risk the possibility of camera shake or movement, resulting in 'out of focus' shots. When mounting your camera on a tripod, switch off shake reduction as this will confuse the camera's electronics. 
Further, cameras that do not come with a shake reduction facility, but one that has, for instance, a zoom lens in the range of 28-200mm, the usual safe hand-held shutter speed for that camera, when the lens is fully extended to 200mm is about 1/250 sec. For a 400mm lens, 1/500 sec. So, you may need to remember these figures and use them for future reference.


See also 'Guide To Sharper Photos'