Article ID : 00018294 / Last Modified : 03/25/2016

How to identify a back focus or front focus issue.

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The following symptoms may be an indication of a back focus or front focus problem:

  • The area just in front or just in back of the subject is sharp, but not the subject you had the camera focused on. The portion of the picture in focus is normally only a few inches in front or back of the blurred subject.
  • The subject is out of focus in photos in both still and moving photos.
  • The subject is out of focus and it is more noticeable on pictures taken with a camera lens that has a large, open aperture setting (lower f-stop numbers) with minimal depth of field.

Keep in mind that the above symptoms are only potential indicators that the auto focus (AF) of the camera might not be working properly. Many pictures that appear to have front focus or back focus problems are caused by human error. Unintentional camera movement or movement by the subject after the camera has already achieved focus lock can cause your subject to appear blurry with the background or foreground in clear focus.

Below is a simple method to test your camera and lenses for front focus and back focus issues.

  1. Make sure you are shooting in an area that has plenty of daylight.
  2. Place five AA batteries on a flat surface at a 45 degree diagonal as shown in the picture.

    Image

  3. Attach the lens you want to use to the front of the camera.
  4. Turn on the camera.
  5. Put the camera into the Manual (M) mode.
  6. Select the Center or Spot AF area setting.
  7. Select a shutter speed of 1/125 or higher.
  8. Select the widest aperture setting (f-stop) available on the lens.
  9. Select ISO 200 or higher.
  10. Mount the camera on a sturdy tripod.
  11. Position the camera and tripod so the camera is level and facing toward the batteries.

    IMPORTANT: Make sure you are far enough away for the camera to achieve focus. It is recommended you be just slightly above the minimum focus distance of the attached lens.

  12. Focus the camera on the center battery.
  13. Take a few pictures.
  14. View the pictures on a computer.

    This is an example of how your pictures should look. Notice that the center battery is in focus, while the batteries in front and behind are somewhat blurred.

    Image

    There may be a front focus issue if one or more of the batteries in front are in focus and the center battery is not as sharp as shown below.

    Image

    If the batteries behind the center battery are in focus and the center battery is not as sharp like in the photo below, there may be a back focus issue.

    Image

Repeat the steps above using a different lens to determine whether the issue is with the lens or the camera body. If the same focus issue reoccurs with a different lens, then the issue may be with the camera body. However, if the issue does not occur with other lenses, then the focus issue is being caused by just the one lens.

You can use a lens alignment tool to fine-tune the focus and help correct front focus and back focus issues. There are a number of commercially available lens alignment tools, including:

If you prefer, there are a number of websites with instructions on how to make your own tool.

Depending on the capabilities of your camera, you may be able to use one of the following methods to resolve front or back focus issues:

Many advanced cameras have a Direct Manual Focus (DMF) option that can be used to fine-tune the focus as needed. Refer to the instruction manual of your camera to determine if DMF is available for your model. Os manuais são postados em seu modelo de página de suporte.

NOTE: If your camera has Focus Peaking it can be used with DMF to help identify where fine-tune focus adjustments need to be made.

If the issue is not resolved, the camera body and/or lens can be sent to Sony for service.