This information applies to version(s): 2018, 2, 3, 4
Nik Collection was never designed to be compatible with RAW files. It was originally designed as a plugin, therefore it is compatible with JPEG or TIFF images using RGB color space. We recommend using DxO PhotoLab as a host software for images from supported camera/lenses and convert to TIFF, or using DxO PureRAW to convert your RAW image from a supported camera/lenses to JPEG.