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In order to get a good photo, the photo
must have a good exposure and the subject is focused correctly.
Autofocus has become a basic function in all digital cameras nowadays.
Some of the lenses have ultrasonic motor for focusing, most with auto
focus assist and some still offer selection of manual focusing. With
the presents of these autofocus system, focusing correctly is no longer
a big problem, though there is still time that we come up with a photo
that is totally out of focus.
Example of a picture that is correctedly focused
Example of picture that is out of focus.
A few things to take note of in order of getting a correct focusing are
discussed below,
Focusing in low dynamic range environment
Basically, autofocus functions by checking on the dynamic range of the
environment and algorithm to ensure the focusing is correct. However
when the subject to be focused having the same exposure level with the
surrounding, the camera might have problem to identify the subject and
lost in focusing. In this case, we can try to focus on something that
has different dynamic range but with the same distance as the subject
to be focused at. This can be done by focusing on the other object,
half press the shutter to focus on that object, switch the camera back
to the object of interest and press down the shutter completely.
Focusing in low light environment
In low light environment, there is a high chance that the camera might
not be able to focus at correctly. For each camera, it needed a certain
level of lighting environment in order to complete the auto focus. Some
digital camera have auto focus assist lamp that help to focus during
low light environment. However the auto focus assist lamp also has its
own limitation as the distance is very short.
The best way to overcome this problem is to attach the camera with an
external flash. External flash have a much better focusing system and
an auto focus assist lamp that can help auto focusing in low light
environment.
Other than this, we can also try to add in external lighting to help,
such as torch light and external lamp. If all this can't help, we might
have to resort to manual focus by using our own hand to tune and eyes
to detect.
Focusing point is not at the center of the frame
A lot of times, the subject to be focused at is not always at the
center of focusing point. In this case, we will have to focus at the
subject first, then re-compose the photo and press the shutter.
However, while doing so, there are chances that the focusing might have
been out slightly as when we are doing re-composition of the photos,
the distance to be focused at might have slight difference. And there
are also chances that we might have picked up a different focus point
while doing re-composition of the photo.
Some camera provides several focus point other than the center point.
In this case, we can select the different focus point according to the
subject that we are focusing at.
The subject to focus at is moving
In a lot of time, the subject is always moving. By the time we finish
focusing at one point, the subject might have moved from the point that
we focused at and result a photo that is out of focus. For example,
when we are trying to shoot photos of kids playing and running around,
it is easily to face with this problem.
DSLR nowadays have the option of choosing continuous auto focusing.
With continuous auto focusing, the camera will focus on the subjects
and continue to focus when the object is moving until we press the
shutter.
There is still some limitation on the continuous auto focus, as the
shutter speed setting might be too long, and continuous auto focus
might not be fast enough to keep in pace with the movement of subject
will still result in photo that is out of focus. Other than that,
another disadvantage is continuous auto focus will consume a lot of
batteries.
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