The Effect Of Image Taking Conditions On Image Quality - Nokia RM-132 Service Manual & Parts Manual

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Sensitivity
Sharpness
Shutter

The effect of image taking conditions on image quality

There are some factors, which may cause poor image quality, if not taken into account by the end user when
shooting images, and thus may result in complaints. The items listed are normal to camera operation and
are not a reason for changing the camera module.
Autofocus
When the camera is focusing a lens is moved inside the module to give the sharpest possible image. This
camera module is specified to operate satisfactorily from 10 cm to infinite distance of scene objects. Trying
to photograph objects closer than 10 cm is likely to result in a blurred out of focus image. The lack of sharpness
is first visible in full resolution images. Images taken very close to the subject, a limited depth of focus will
be visible, that is the upper or lower parts of the image may be out of focus. This is normal; do not change
the camera module.
Figure 60 Only center part of image is in focus due to limited depth of focus
The amount of light available
In dim conditions camera runs out of sensitivity. The exposure time is long (especially in the night mode)
and the risk of getting shaken (= blurred) images increases. In addition, image noise level grows. The
maximum exposure time in the night mode is ¼ seconds. Therefore, images need to be taken with extreme
care and by supporting the phone when the amount of light reflected from the target is low. Because of the
longer exposure time and larger gain value, noise level increases in low light conditions. Sometimes blurring
may even occur in daytime, if the image is taken very carelessly. See the figure below for an example. This
is normal; do not change the camera module.
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Camera module's sensitivity to light. In equivalent illumination conditions,
a less sensitive camera needs a longer exposure time to gather enough
light in forming a good image. Analogous to ISO speed in photographic
film.
Good quality images are 'sharp' or 'crisp', meaning that image details are
well visible in the picture. However, certain issues, such as non-idealities
in optics, cause image blurring, making objects in picture to appear 'soft'.
Each camera type typically has its own level of performance.
The electronic shutter is used when short exposure times are needed and
in video. When the mechanical shutter is used a black sheet will cover the
lens after the exposure.
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RM-132; RM-133
Camera Module Troubleshooting
Issue 1