Here is my review of the Optoma UHD65 4K projector compared to my Optoma HD29Darbee 1080p projector. The HD29 has Darbee processing to improve the image and that does make a difference, especially for blurays, but not so much for regular TV. The pics I've included are from a YouTube 4K video, which I will explain later.
To set the stage, I have the HD29 mounted on the ceiling and the UHD65 set on the floor almost directly underneath the HD29. Both projectors use full zoom to get the biggest image and set closest to the screen as possible. My screen is a Dalite HighPower 159" 2.5 gain screen. It is retro-reflective--meaning the reflected light tends to reflect back to the source. Since I sit lower than the HD29 and higher than the UHD65, the brightness back to me is about the same for each projector. The UHD65 was set on HDR normal brightness mode, and the HD29 was set on ECO brightness mode. Both are set to about the same brightness and contrast to the eye.
First, I hooked up Xfinity cable to the UHD65 and was surprised by the upscaled image. While it was very clear, it was soft and smooth looking. When standing next to the screen, I could barely see the individual pixels as the dithering caused by the shifting TI chip made the image smoother. I didn't like the image. While I could see more detail, I also lost definition in objects like grass, and peoples faces up close. Where I could clearly see the pores on peoples faces, I could no longer see that with the UHD65. I tried to watch the golf match, but just didn't like the smoothness. I tried to increase sharpness, but that didn't help either. I then tried to watch another channel with a movie, and that was awful as it smeared fine lines. This is probably due to the cable not sending a true 1080p image and the upscaling of the UHD65. I switched back to my HD29 and that was easier to watch. Others might like this smooth image, especially if you never have had a 1080p DLP before, but I did not. So that was the first strike.
I then hooked up a 4K Samsung K8500 bluray player to the UHD65 and a Sony high-end bluray to my HD29. I had a friend, who is not a video fanatic and knows little about projection TV, as a second opinion. We watched several 4K Youtubes on the UDH65 and were wow'd by them. I checked to make sure that the projector was seeing 4K and it was. I then turned off the UHD65 and turned on the HD29, and loaded the same 4K youtube videos, which got downscaled to 1080p/60fps. I had my back turned initially, and my friend said, "I thought you were going to show these on your other projector?" I said, it is on the other projector. I turned around, and was baffled. The video didn't look that much different. There was a slight edging problem with diagonal lines as I've always seen on 1080p projectors, but other than that, the video was as satisfying as the 4K video on the UHD65. I gave that a big, "Hmmm." Strike two.
We then watched some scenes from 4K Passengers on the UHD65, and it was great but smooth looking. Then I switched to a 2D 1080p bluray of Passengers on the HD29. Again, we didn't see that much difference and the UHD65 image came off as too smooth looking for my taste. We then watched Passengers in 3D on the HD29 and were convinced that that was much better than watching the 4K 2D version on either projector. Score one for 1080p 3D!
I then set up a compare of a 4K youtube SpaceStation glide through and took some cellphone pics from my Samsung 8. Because of shooting in the dark, I lost some sharpness, so take that into consideration. I did note that the UHD65 pics showed more color variation than the HD29, so that was one plus for it. The dark contrast was about the same for both, and I did not see any advantage to HDR as well. The first two emblem images below were taken about 1 foot from the screen. It's obvious which is the UHD65 image. You can barely see the pixels, whereas in the HD29 image, they are very prominent. From our seating position of about 16 feet away, the emblems looked the same. Neither were readable at that distance, but looked like they had the same definition. You will see in the two compares where there is an overlay of the schematic of the space station abd the HD29 does a reasonable job of defining the lines as well as the UHD65. Visually from 16 feet, we couldn't tell much difference in the images. There is a lot going on there as well with all the wires and mash of objects everywhere. If you zoom in on the images, you will definitely see there is more detail in the UHD65 images, but at 16 feet, we were not seeing it.
Final conclusion: I'm sending the UHD65 back. I was going to possibly use it for upscaled 1080p along with the HD29 for 3D, but the upscaled 1080p is a waste of money. I have a 60" 4K passive 3D LG in our living room, and it does a much better job of making normal cable look like 4K, possibly because of the size difference in images, but more likely because of the lack of dithering with the TI chip, which must take 1 1080p pixel and divide it into 4 discrete 4K pixels, which, along with dithering the pixels adds an element of smoothness rather than definition. This just proves to me that a true 4K panel like the Sony is the way to go, so I will be waiting for the future of an inexpensive true 4K with 3D projector.
I'm beginning to think the reason Optoma and others have not implemented 3D on the new 4K XPR projectors is the fact the a 1080p 3D image can't be created properly using the x-shift without making the image soft, which would be awful for 3D.