Philips BDP7501 HDR to SDR Color Conversion Errors
I recently purchased a Philips BDP7501 UHD BD player to use in my audio and video calibration business. This is a very well built player and I definitely prefer it’s operation to the Samsung UBD-K8500. I have not tested the Samsung’s ability to convert HDR (high dynamic range) to SDR (standard dynamic range), but I can say the Philips is desaturating the colors in the image pretty dramatically. Below is a chart showing the primaries versus their targets on a very accurate SDR display outputting Rec. 709 primaries from a UHD HDR BD.
If this conversion was done well the triangles (measured values) in the chart would be close to the squares (target values) for each color measured. This is much worse than this display is capable of. Color space conversion in general has been problematic due to errors in the published SMPTE color conversion equations (1). With the large changes in color space and EOTF (electrical optical transfer function or gamma) today the errors are too large to ignore. Hopefully, this can be corrected with future firmware updates to these products.
I would not recommend playing back 4K/UHD HDR content with displays that do not support BT2020 color space until these problems are resolved.
1 – Lars Borg, “Better Color Matching Between HD and UHD Content”, SMPTE Motion Imaging Journal, April 2015