[Magick-bugs] Regression regarding 16-bit grayscale DPX files

[omicronpersei8 at imagemagick.org]

> instead of a 16-bit, gray, 1-channel image

ImageMagick thinks the image is in the Log colorspace.  It cannot be
in Log and Grayscale at the same time.  We will check the DPX tags and
verity if the image is indeed in the Log colorspace.