> > Visually the noise pattern looks completely static - ...
Alexander, what you see is really sensor "fixed-pattern noise" - the different dark signal from the sensor. The pixels that seem white are really what is called "warm pixels" - the ones that have significantly higher dark current than the others (some chip defects). For short exposures this effect is not that visible as even increased dark current does not provide enough charges. At short exposures only "black"(always 0) and "white" (always saturated) pixels are important. When you close the iris (or the lens) with default camera settings it increases exposure to maximal (default limit is 0.5 sec - it can be adjusted), so you probably made those images with 0.5 sec exposure. If you send the monochrome JPEG image (set mode to "mono" in user interface) and set 100% image quality you will get virtually lossless file with Exif header that includes multiple parameters, including exposure time and analog gains. Actually for monochrome sensors I would recommend using that 100% JPEG in "mono" mode over "raw" - it will be much faster and there will be no compression loss - 100% in Elphel cameras means literally 100% (as suggested by JPEG) - all quantization coefficients are equal to ones, so no quantization is actually performed on the image data. Color sensors benefit from JP4 mode that preserves Bayer color mosaic while having good compression ratio. If you really plan to work with lonfg exposures you can use background subtraction - either on the host computer or using FPGA code that allows to subtract fixed patters during image acquisition. BTW, here is the command to convert the camera raw files to PNG (or others) with Imagemagick: convert -size 2596x1940 -depth 8 gray:image1.raw image1.png Andrey
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