Testing Camera Image Sharpness; Dirty Camera Lens Protection Window - Nokia 301 Service Manual

RM-839; RM-840; RM-841
Camera Module Troubleshooting

Testing camera image sharpness

Symptoms and diagnosis
If pictures taken with a device are claimed to be blurry, there are six possible sources for the problem:
1 The protection window is fingerprinted, soiled, dirty, visibly scratched or broken.
2 The photographed object is too close – the camera lens operates with distances from 20 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 the protection window and camera lens.
5 The protection window is defective. This can be either a manufacturing failure or caused by the user. The
window should be changed.
6 The camera lens is misfocused because of a manufacturing error.
7 Very high level of digital zoom is used
A quantitative analysis of sharpness is very difficult to conduct in any other environment than optics
laboratory. Therefore, subjective analysis should be used.
If no visible defects (items 1-4) are found, a couple of test images should be taken. Generally, a well-
illuminated typical indoor scene can be used as a target. The main considerations are:
• The protection window has to be clean.
• The amount of light (300 – 600 lux (bright office lighting)) is sufficient.
• The scene should contain, for example, small objects for checking sharpness. Their distance should be 1
– 2 meters.
• If possible, compare the image to another image of the same scene, taken with a different device. Note
that the reference device has to be a similar Nokia phone.
Steps
1. Take several images of small objects in the distance of 1-2 metres.
2. Analyse the images on a PC screen at 100% scaling with the reference images.
Pay attention to the computer display settings: at least 65000 colors (16-bit) have to be used. True colour
(24-bit, 16 million colours) or 32-bit (full colour) setting is recommended.
Next actions
If there appears to be a clearly noticeable difference between the reference image and the test images, the
module might have a misfocused lens -> change the module.
Re-check the resolution after changing the camera module.
If the changed module produces the same result, the fault is probably in the camera window. Check the
window by looking carefully through it when replacing the module.

Dirty camera lens protection window

The following series of images demonstrates the effects of fingerprints on the camera protection window.
It should be noted that the effects of any dirt in images can vary much. It may be difficult to judge whether
the window has been dirty or if something else is wrong. Therefore, the cleanness of the protection window
should always be checked and the window should be wiped clean with a suitable cloth.
Issue 1 NOKIA INTERNAL USE ONLY
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