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cjs30 Nov 15, 2005 7:49 PM

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Dear All,

I have just bought a Minolta Dimage Z2. My first one had dust visible through the eyepiece, probably on the reflectorof the LCD screen -so I had it exchanged. But, the replacement has some 'hot' pixels almost in the middle of the CCD. (x1064, y764)I have attached an image of the moon (at reduced resolution) which shows the problem. It was taken at 1/1000s and f/8, the four pixels can be seen in the top third of the moon just to the left of the midline.
The moon is about as bright an object as one can sensibly photograph with a standard digital camera without modifications. Given that these'hot' pixelsoccur even at the shortest exposures possible, they are going to be visible in every image I take.

Here is the question;"Should I just accept it?" or "Can I reasonably expect a better replacement?"

Any advice would be gratefully received.



viggen Nov 15, 2005 10:15 PM

Hi, csj30. This is not a hot but a stuck pixel. Hot pixels appear at long exposures, stuck ones remain "on" in all images and at any exposure time. And if one pixel is stuck, then, in a Bayer pattern camera (a normal one), the surrounding pixels will be affected. So, you get a block of at least 4 bad pixels in the final image, depending on image processing and compression.
Go in service and they will remap the stuck pixel or exchange your camera.

cjs30 Nov 16, 2005 5:13 AM

Yes, I think you must be right about it being a stuck rather than a hotpixel. The value of ~64 grey levels (at 1/1000s) from the block of fourpixels (shot with the lens cap on)should have told me that each pixel in the image comes from an average of four pixels on the CCD and one was stuck high (256/4 = 64). I had thought it might be hot because the pixel values rose as the exposure was lengthened - but that is simply because the outer neighbouring pixels began to contribute some signal. Well, I have learnt something.

I have been to see the retailer, and theyhave kindly offered to replace the camera.

In the meantime I did consider writing a simple batch program that subtracts 64 from the block of four bright pixels (a trivial bit of visual basic programming). I have seen programs 'out there' that do hot and stuck pixel correction - but since I know where the pixels are I don't need anything fancy.

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