The Effect Of Image Taking Conditions On Image Quality - Nokia RM-51 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.
Distance to target
The lens in the module is specified to operate satisfactorily from 40 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 40 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.
Sharpness of picture edges
The lens performance degrades in image edges, and generally the image is sharpest in the center part.
Particularly this applies to distant objects (> 1 meter).
See the following figure.
Figure 160 Picture sharpness is worse on the edges than in the center
Geometrical distortion
The camera lens causes some amount of so called barrel distortion in images.
In practice, this appears as bending of straight objects on the edges of an image. See figure
shaking hands (Page 8–7)
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.
Page 8–6
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.
(wall in the background).
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Camera module troubleshooting
Blurring caused by
9238460 (Issue 1)
RM-51