The Effect Of Image Taking Conditions On Image Quality - Nokia 2630 RM-298 Service Manual

Sensitivity
Sharpness

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.
Distance to target
The lens in the module is specified to operate satisfactorily from 20 cm to infinite distance of scene objects.
In practice, the operation is such that close objects may be noticed to get more blurred when distance to
them is shorter than 20 cm. The lack of sharpness is first visible in full resolution images. If observing just
the viewfinder, even very close objects may seem to appear sharp. This is normal; do not change the camera
module.
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 or high levels of digital zoom, cause image blurring, making
objects in picture to appear 'soft'. Each camera type typically has its own
level of performance.
Figure 90 Blurred image. Target too close.
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RM-298; RM-299
Camera Module Troubleshooting
Issue 1