Instead of simply appending ".tiff" to the existing filename (like
`dcraw_emu` does), `dcraw` fully replaces the file extension, leading
`convert` to subsequently fail as it can't find the `.dng.tiff` file.
Redirecting streams using `&>` is not POSIX-compliant. This causes some
shells (such as `dash`) to evaluate `if` conditions the wrong way.
Sticking to standard `>` redirection fixes this issue.
Arnaud Ferraris
Martijn Braam