The Effect Of Image Taking Conditions On Image Quality - Nokia RM-42 Service Manual

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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.
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 (1600 x 1200) 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 79 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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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.
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Camera Module Troubleshooting
9241872 (Issue 1)
RM-42