2013-02-13

Top tips for accurate focusing

Focus points as seen through
a typical DSLR’s viewfinder.
All Digital SLR cameras utilize an auto focus system that employs multiple focus points, the exact number depending on the make, model and ultimately price point of the camera. The number of focus points tends to differ from as little as 3 found on lower specified models to 63 found on the highest spec / most expensive models.

However regardless of these factors one problem that Digital SLR owners tend to experience is the cameras tendency by default to focus on the subject closest to the cameras as opposed to the subject required.


In this instance the camera has chosen to employ multiple focus points,
focusing on the subject closest to the cameras opposed to the most important
subject in this case the tiger’s eyes
In order to overcome this problem it is necessary to switch to an exposure mode which allows a specific focus point (s) to be selected manually, these modes generally tend to be Program, Semi Automatic (Aperture or Shutter priority) or Manual.
Auto area is the default setting as used on all DSLR models 
Manual point focus selection is available on all DSLR models in
Program, Semi Auto or Manual
Focus mode selection available on a Nikon D90 
Focusing point confirmation Some of the higher spec modes of DSLR camera allow for the facility to display the focusing point on the rear of the camera’s LD screen, this facility however has to be enabled within the menu of said models (applicable to certain Canon & Nikon models i.e. Canon 60D, 7D, 5D Mk III and Nikon D90, D7000 etc).
AF Point display is required to be enabled in order to view the chosen focus point on playback.
Single focus point chosen to ensure accurate focus,
in this case the image  of portraiture this is essential.
Confirmation of focus point selection via software The software that is supplied with the camera (Canon & Nikon) also allows for the focus points to be displayed (this is however dependent on the resolution setting chosen, with the Canon DPP software in order for the focus points to be displayed it is necessary to shoot in RAW).

Software options that are able to display the appropriate focus points chosen at time of focusing include the following:
  • Canon - ZoomBrowser and Digital Photographic Pro (DPP)
  • Nikon – Nikon View NX, NX2
  • There are also third party manipulation programs that are also able to visually display the appropriate focus points used, these being 
  • Breeze Browser 
  • Apple Aperture 
The following focus options are available at the time capturing the exposure, careful consideration should however be taken in choosing the appropriate option.
  • Auto Selection – focus target(s) chosen by the camera 
  • Manual focus point selection by the user 
  • Selection of manual focus point i.e. centre point and recompose 
  • Focus manually 
Focusing Recommendations
Portraits
Use single point and focus on the subject’s eye – recommended to use one shot auto focus as this will prevent the camera readjusting the focus if the image is recomposed

Groups
For groups it is strongly advisable to choose auto area (default mode as used by all cameras unless otherwise set). If shooting a group of people the camera will tend to choose multiple focus points, do not be surprised if the camera employs all the focus points that are available, the camera will average out the focus accordingly.

Landscapes Single focus point can be employed for landscapes, with the user normally selecting the centre focus point to ensure a greater depth of field.

Sport If using a lower spec model in which it is not possible to select a group of images it is advisable to choose either a single focus point for subjects that are predictable in terms of their movement or auto area if unpredictable. If using a higher spec model it would be possible to select a group of focus targets applicable to the size and range of movement of the subject. In both examples continuous as opposed to single shot auto focus should be used as this will allow for the predictive auto focus system to track and adjust focus from shot to shot.

Night time / Low light Due to the issues of low light and lack of contrast and the associated problems this brings manual focus would be an advisable option to use for shooting night time scenes at a distance or fireworks.

Single shot or Continuous Auto Focus
There are further options with regards auto focus to consider when using the camera, this being the choice of either single shot autofocus in which the camera will focus once or once only (recommended for portrait and still life) or Continuous or Servo autofocus in which the camera will adjust the focus in line with subject movement. The servo mode utilizes a predictive system which allows the camera to calculate speed and direction of movement, this is known as Predictive autofocus.

All of these focus options are covered extensively in our School of Photography camera courses run by our in-house tutor Anthony Sinfield. These inslude:


Anthony Sinfield

School of Photography Training Manager

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