Cause Identification Procedure For Focus-Related Problems - FujiFilm FinePix S3Pro Service Manual

5. Inspection
5-6-4.

Cause identification procedure for focus-related problems

With the FinePix S3Pro, queries and complaints regarding focusing and auto focusing (AF) address a wide range of overlapping
factors. These factors include the shallow depth of field for the subject due to the increased resolution of the CCD (the permissible
circle of confusion (see figure below) is smaller than that for a conventional camera), the fact that digital images can be viewed
enlarged on a PC, the differences in the way images are generated compared with the FinePixS1Pro, lens-related factors and
problems that arise due to the way the camera is used. For this reason, methods for differentiating between these various factors
are discussed here.
What is the "permissible circle of confusion" ?
A lens resolves the image of a subject located on the optical axis on the image plane. But we often see that subjects at a range
of different distances from the camera, both nearer and further away than the focal distance, are also in focus. This is because
when the degree of blurring in a subject is below a set amount, we perceive the subject as being in focus. This set amount is
known as the permissible circle of confusion. The range on either side of the image plane within which the amount of blurring is
smaller than the permissible circle of confusion is called the depth of focus. Similarly, the subject range for which the image is
resolved within the depth of focus is called the depth of field. All subjects within the depth of field for a shot are photographed as
if they were in focus.
Rear depth of field
Depth of field zone
<Cause identification procedure>
The basic causes underlying detected problems can be broadly grouped into 3 categories, as outlined below.
(1) Problems attributable to how the camera is used
• Resolution setting
--> Can be resolved by selecting a high-quality mode (12M JPEG-Fine, RAW) in the resolution settings.
• Sharpness setting
--> Check the resolution problems in SOFT mode.
• Diffraction when shots are taken using an excessively small aperture
--> Check the F-stop setting and try taking the shot with an aperture that is slightly larger than the one causing the problem.
*1 Diffraction refers to the tendency of light to scatter due to its wave-like properties. By reducing the aperture size (stopping
down), the proportion of the direct reflection light that is resolved directly onto the CCD surface decreases and the effects
of diffraction become noticeable.
• The focusing performance for the focus target deteriorates slightly in all 4 directions (up, down, left and right) when compared
with the center of the image because the AF sensors detect light horizontally.
--> The central focus area should be used to focus the shot.
• ECamera shake
--> The use of a tripod is recommended.
• Photographing subjects that are difficult to focus
--> As described in the Owner's Manual, use manual focus for objects that are not suited to auto focusing.
(2) Problems attributable to faults in the FinePix S3Pro
• Problems in the Camera Body (AF function defects, body flange back defects, viewfinder matt screen offset, etc.)
--> Perform AF checking and the Camera Body is repaired.
(3) Problems attributable to performance limitations or defects in the lens used
Using the checking lens as reference, determine whether the problem is with the lens or with the FinePix S3Pro.
• Lens AF malfunction (cannot be addressed by Fuji)
• Lens performance (cannot be addressed by Fuji)
--> Get the lens manufacturer to check the lens being used.
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Focal length
Front depth of field
*1
FinePix S3Pro Service Manual
Permissible circle of confusion
Depth of focus
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