Philips BDP7501 HDR to SDR Color Conversion Errors
Posted July 27, 2016 by W. Jeff Meier under Sources
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
I have noticed this with both the Samsung and Phillips players. I wasn’t sure how to describe what I was seeing, but felt saturation could be the issue.
I did perceive what I felt was an improved picture by increasing the color setting on my display, though this of course affects the image from other sources and I have no idea about the accuracy of what I was seeing.
It’s not ideal, but for a few titles I am willing to deal with it for the Atmos/DTS:X available only on the 4k discs. Hopefully, firmware updates are forthcoming.
I know this is an old post, but did Philips ever fix this?
I have not seen a fix for this. I created special settings in some displays to improve the color accuracy for conversion from HDR to other formats.