Been years since I posted on this site, but thought I'd chime in regarding this player.
I've owned a Sony 75-inch 940E and LG UP970 4K blu-ray player for the last couple of years. Last week, I decided to upgrade my blu-ray player to the Sony X700 so that I could take advantage of the Dolby Vision low-latency profile that's compatible with my TV. I own a few DV discs such as Justice League, the Matrix trilogy, and the Jack Ryan collection. My HDMI cables are Premium Certified 18GPS from Monoprice.
Upon setting up the X700 player to output DV, I noticed the picture appeared excessively dark. HDR highlights on both DV-encoded discs and regular 4K discs were totally clipped, and everything appeared oppressively dim. Boosting my TV settings to brighten up the picture did little to rectify the issue. By comparison, disabling the DV setting on the player and outputting a standard HDR10 signal resulted in a bright, vibrant picture. I also viewed DV content via the TV's internal Amazon app to watch some of Amazon's original Jack Ryan series since it's encoded in DV. The picture quality was outstanding--no darkened picture.
I decided to return to the Sony X700 and replace it with the Panasonic UB820.
Night and day difference, folks.
The picture quality on the UB820 is everything it's been cracked up to be. DV discs appear bright and vibrant and offer a "pop" that's almost hypnotic. Regular 4K discs also appear incredible. For that matter, so do standard blu-ray discs. This player trounces both the Sony and LG players and has made me fall in love again with watching 4K movies.
I'm not sure what's going on with Sony. You'd think their 4K blu-ray player would work perfectly with one of their own TVs. However, it's Panasonic that's delivered the goods. Unfortunate that I had to spend considerably more for this player over the Sony, but thankfully BB just dropped the price by $50 over the weekend during a sale. Highly recommended to anyone sitting on the fence.