Nokia RM-12 Troubleshooting Instructions page 84

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er wipe the lens surface before trying compressed air; the possibility of damaging the lens is
substantial. Always check the image sharpness after removing dust.
Testing of sharpness
If pictures taken with some device are claimed to be blurry, there are four possible sources for
the claim:
1 Protection window is fingerprinted, soiled, dirty, visibly scratched or broken.
2 User has tried to take a picture of a too close object – lens operates with dis-
tances from 40 cm to infinity. This is no cause to replace camera module.
3 User has tried to take pictures in too dark conditions and images are blurred due
to handshake or movement. This is no cause to replace camera module.
4 There is dirt between protection window and camera lens.
5 The protection window is defective This can be either manufacturing failure or
caused by user. Window should be changed.
6 Camera lens is misfocused due to manufacturing error.
Quantitative analysis of sharpness is very difficult to conduct in other than optics laboratory en-
vironment. Thus subjective analysis should be used.
If no visible defects (items 1-4) can be found, a couple of test images should be taken and
checked. Generally, a well illuminated typical indoor office scene, such as the one in Figure A
good picture taken indoor, can be used as a target. The main considerations are:
• The protection window has to be clean
• Amount of light: 300 – 600 lux (bright office lighting) is sufficient
• The scene should contain e.g. small objects for checking sharpness
and distance to them should be in order of 1 – 2 meters
• If possible, compare the image to another image of the same scene,
taken by different device. Note that comparison device has to be similar
Nokia cellular phone.
The taken images should be analyzed on PC screen at 100% scaling simultaneously with ref-
erence image. Pay attention to the computer display settings; at least 65000 colors (16 bit)
have to be used. 256 (8-bit) color setting is not sufficient, and true color (24 bit, 16 million
colors) or 32 bit (full color) setting is recommended.
If there appears to be a clearly noticeable difference between the reference image and the test
images, the module might have misfocused lens. In this case, the module should be changed.
Always re-check the resolution after changing the camera. If a different module produces the
same result, the fault is probably in camera window. Check the window by looking carefully
through it when replacing the module. As a reference image A good picture taken indoor and
Issue 1 11/2004 Copyright©Nokia. All rights reserved
RM-12
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