Sigma sd Quattro JPEG File Quality in Black and White + sd Quattro JPEG bug in Black and White + fix
See my Sigma mirrorless wish list at B&H Photo.
With the challenges presented by the Sigma Photo Pro software when dealing with X3F raw files, Sigma sd Quattro users might consider JPEG if the image quality is there.
Includes the six black and white in-camera JPEG variants plus a reference black and white image made in Photoshop from an RGB JPEG, at up to full camera resolution.
The results from the camera are awful: the in-camera black and white variations are unacceptably dark. This in spite of them having a full-range histogram from black to white. This appears to be a BUG related to color space, but that is only a guess. In essence, it looks like the sd Quattro is processing into some grayscale colorspace, but tagging it as AdobeRGB. Or something like that.
A mitigation/workaround fix in Photoshop is shown, which results in far better results, but to my eyes, the conversion from the color JPEG in Photoshop is the best of all.
Black and white JPEG bug aside, that the Sigma sd Quattro makes for an outstanding color or black and white camera is plain to see (at least at ISO 100). Detail is outstanding, well beyond what any Bayer matrix camera can deliver for this number of pixels.