QHYCCD

Overscan region used for dark calibration

Overscan region used for dark calibration
« on: July 30, 2020, 05:02:11 PM »
We have a 168C camera. In short: Does the Bayer filter array pattern matter if one is using the overscan region to determine the dark level background? -Jesse

In long: LibRaw is coming out with a new version of their raw image library for standard DSLR cameras. From the release notes (https://www.libraw.org/news/libraw-0-20-Release):

Bayer images: ensure that even margins have the same COLOR() for both the active sensor area and the full sensor area.

(Where: overscan = full - active). This means that for some cameras the Bayer matrix effectively gets offset by a pixel over earlier versions. The implication of this, as I understand it, is that the value of an overscan pixel depends on the filter color overlying it. So, an RGGB arrangement will return different overscan values than a GRGB arrangement. This doesn't make sense to me as I would think since the overscan region is not illuminated there should be no difference which Bayer filter color is above any given pixel. Is anyone at QHY aware of how or why the filter pattern in the overscan region would be important?