I work in the home theater industry and have installed a number of high end projectors, so I think I know a little about this subject. It really depends on how much you are willing to spend, but the new JVC 4k projectors are very very good. They will run you somewhere between 5 and 12 thousand. Sim2 (who makes some of the best home theater projectors out there) also makes a 4k projector, but it is really expensive, in the neighborhood of 80-100 thousand i believe.
I'm assuming the OP is asking about real 4K projectors and not pseudo-4K like the JVC's. I have a JVC projector and will more than likely buy another in the future (love the black levels). But, I doubt I'm going to buy another projector unless it does real/native 4K.
About the only "consumer" grade 4K projector is the Sony. Fine projector. I'm holding out for other real 4K projectors that are less than $10k. Ideally, less than $5k. Hopefully, in the next 2-3 years that will be a reality.
If the OP is going to drop $50k+ on a projector, I'd hope he'd do his own research to make sure the throw ratio and such meet his needs and not ask on a tech forum where, let's be honest, most people don't know squat about 4K, as evidence by the "nobody needs 4K" rants.
Actually the new DLA-x500r, DLA -x700r, and DLA x900rkt are all real/native 4k projectors, they have native 4k hdmi inputs. And the 500 goes for about $5000.
You do bring up some good questions in your other post though. With the limited information given by the OP, we can really only give a limited answer.
PuppiesOnAcid: May I suggest you do more research before correcting other people? JVC projectors are not native 4K projectors that is the panel inside is only 2K. They receive 4K signals but that does not make them native 4K. So unless you want to change the resolution definition, the industry has chosen since the beginning, the 4k resolution is NOT defined because the projector can receive 4k HDMI or does e-shift.
Nice question, but to vague to be actionable.
There are far too many variables. If you need some real help, I'd suggest you go over to the AVSForums.
Some things to think about:
1. Do you have or plan to have an anamorphic lens?
2. Do you need/want auto zooming for different aspect ratios (or do you have an auto-masking screen)?
3. Is your room light or dark? Do you need more or less lumens?
4. How big is your screen? (see above for lumens requirement)
5. Do you need scaling on the projector (or do you have an external scalar) ?
6. Do you need calibration on the projector or do you have an external calibration source (like a Lumagen)?
7, etc.. etc.. etc..
what ever you get make sure it has hdmi 2.0 the bigest complaints i hear about 4k boil down to not enough fps and 60hzs vs 30hzs can make a big difference. i know Panasonic released one and Sony announced one
all the 4k problems compound when you start looking at cameras
Get the Panasonic. The reviews are in and the best thing about it... is that is makes NON-4k sources look good. Very important for early adopters.