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A Perfect M8 Sensor


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Just got my sensor replaced a few months ago under warranty due to the infamous dead pixel causing line in images issue, and I thought I could be happy for a while until recently ...


I have discovered a new dead pixel in the new sensor that seems to be causing the emerging of a line... actually the line is not so visible yet, but I can see it at high iso...


What wonders me is - does the new sensor Leica uses to replace dead pixel stuck one really improved in the sense that it will unlikely to cause the line? I mean I can totally bear with a few dead pixels as long as they do not cause lines to appear in images...


Are there any perfect M8 sensor out there?? It makes me feel sick thinking about having to replace it again knowing that new one will have the same problem again! If you find yourself in similar situation, what are you gonna do?

Edited by badpets
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There's no such thing as a perfect sensor. The M8 sensor is allowed to have up to 2500 defective pixels and there are rules explained in the Kodak documentation about how closely spaced they can be while still remaing a "good" sensor. Dead columns are also allowed in a sensor but saturated columns are not.


During manufacture, the camera is "taught" where the sensor defects are and will mask them out by interpolating across the defect. The allowable density is set to make the repairs invisible in practice.


This is fine providing the sensor is stable but if there's some sort of contamination or aging process which will make more defects appear over time, repeated calibrations will be required.


I'm sure Leica have comprehensive software to analyse the sensor output on a test rig and determine whether visible sensor defects require a replacement sensor or just a recalibration. I expect there are a number of users out there who think they had a replacement sensor where actually all that happened was a recalibration to mask out the defects. Nothing underhand in this, no sensor is perfect so the camera has to be able to deal with the defects.


[The Epson R-D1 (in its "S" level firmware) has a user procedure for dealing with this; I seem to remember it was done with the lens cap on but when such a procedure is only done at the factory, there's scope for different test conditions and much more comprehensive analysis.]

Edited by marknorton
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marknorton, thanks for the explanation! i know there's no such thing as perfect sensor; i titled it to fulfill my silly desire for a perfect sensor so i dont have to worry about it ever again! i guess i would be waiting for the problem to get worse and then with no choice but to send it for sensor replacement again. i dont know how they do it, i really hope they can develope some kinda firmware to map out the lines caused by dead pixel.

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