Ever since 4K TVs hit the scene a few years ago, home theater fans have been drooling at the idea of projectors with 4K resolution. The visible improvement in even big TVs is marginal at best, but a massive projection screen seems like a much better use for all those pixels.

Today you can get a 4K TV for $300, but projectors have taken a lot longer to get 4K to mainstream prices. Since 2012 or so Sony has been selling 4K projectors, but it's pretty much the only one. Its units have come down in price from $25,000 at the time to $5,000 today, but that's still hardly "affordable."

Then, in late 2017, the first 4K projectors appeared that cost less than $2,000, and now you can get one for $1,500. That's about the same as a decent 75-inch 4K TV, but with a projector you can blow that 4K image up to 120 inches or more.

So how'd they get so cheap, and why now? Turns out there's a clever trick.

'True' 4K vs. pixel mind tricks

On almost all 4K TVs, the 3,820x2,160 pixels are separate discrete little picture units, and if you look closely (or use a magnifying glass) you can see them all. Projectors, meanwhile, use DLP, LCD or LCoS/SXRD chips to create the image. The pixels on those chips are incredibly tiny, hundreds of times smaller than on a TV. Making stuff smaller can be expensive, which is one reason Sony's projectors, which actually do have all those discrete pixels, continue to remain out of reach for most buyers. 

Manufacturers of less expensive projectors have come up with a different method to get prices down: The chips that make the image aren't actually 4K. Or to be more specific, the chips don't have 3,820x2,160 discrete pixels. Instead, they use lower-resolution imaging chips and some additional method -- basically, a trick -- to create 4K onscreen.

Two projector makers, Epson and JVC, have been doing this for years and are fairly upfront about the fact that they're not actually 4K. 

Epson uses three 1,920x1,080 LCD chips, one for each color, and then offsets each pixel slightly so it appears as a different pixel on screen. This is done very quickly, so to your eye, it's just a higher-resolution image. I asked Epson to explain what technique they use to do this, either optical, mechanical, or magical. They wouldn't say. I'm pretty sure it's not the latter, my guess is the former. They call this tech "4K Enhancement," though they're also clear in their marketing that the projectors' native resolutions are 1,920x1,080 with the fine print reading "4K Enhancement Technology (4Ke) shifts each pixel diagonally to double Full HD resolution." The cheapest current Epson projector with 4K enhancement is the HC 4000 ($1800).

Most of JVC's D-ILA projectors do a similar diagonal shift, running at 120 Hz. It calls the latest version of this "e-shift5 4K Precision," which works similarly to previous generations, though with each it claims the improved processing and, correspondingly, improved performance. The cheapest is $4,000.

4K DLP is done with mirrors

Just about every consumer projector that's not Sony, Epson, or JVC uses a DLP (Digital Light Projection) chip from Texas Instruments. There are three new single-chip DMDs  that companies can use to build a 4K projector: 

• DLP660T: 0.66-inch size, 2,716x1,528 discrete pixels 
  
• DLP470TE/DLP470TP: 0.47-inch size, 1,920x1,080 discrete pixels
  

On a DLP chip the physical discrete pixels are actually tiny mirrors. The 660TE is larger and has more pixels, and each of its mirrors creates two pixels on the screen. The smaller 470 chips have fewer pixels, with each mirror creating four pixels on the screen. And yes, TI claims that with both DLP chips, you're getting over 8.3 million pixels onscreen.

So is the image really 4K? Well... yes and no. The pixel "multiplication" happens so quickly that your brain combines it all into a single, high-resolution image. Will this appear as more detailed than the same technology (e.g., LCD, DLP or LCOS) but in 1080p guise? Yes, probably. Would a same-technology but "true" 4K projector look even more detailed? Depends on the technology and implementation.

By the way, if you go into the really high-end of DLP projectors, the kind that goes into multimillion-dollar home theaters, you can get a 3-chip DLP that has 3,820x2,160 mirrors on each. The cost of the additional and larger chips, along with the extra manufacturing effort to get the three panels to align correctly, accounts for the higher prices of these projectors. It's worth noting that DLP movie theater projectors, if they're 4K, also use three true 4K chips.

Resolution isn't everything

The most important thing to remember is that numerous other factors beyond resolution will determine the projector's overall picture quality. That means there are other aspects to projectors that would be more worth your money beyond 4K resolution: higher light output, better optics/lenses, higher contrast ratios, lower noise, longer lamp life, better color and so on. These would create a far better-looking image, regardless of resolution. And those aspects will apply to all content the projector displays, not just stuff in 4K.

A good example is CNET reviewer David Katzmaier's 2015 comparison reviews between the Sony VPL-VW350ES, a true 4K projector, and the JVC DLA-X700R, a 1080p projector. He gave the overall nod to the JVC because of its superior contrast, and had a very difficult time discerning the extra resolution of the Sony with most stuff he watched.

My 4K sense

I've been using a projector as my main TV for going on 15 years now. I started with 720p projectors, moved on to a few dozen different 1080p models, and just a few months ago, a lightly used Sony 4K. 

The biggest differences, strictly from a resolution standpoint, is twofold. The first, and most obvious, is an increase in fine details. You'll see more individual strands of hair, more wrinkles, more textures in fabrics. Despite a 4x increase in pixels, the actual subjective improvement in the image is more like 15-20 percent. It's nice, but it's just not that big of a deal to me, even on a 100-inch+ screen. If, say, you got a projector with 4x the contrast ratio, that would be a much greater subjective improvement. 

The other aspect, and the one I notice more, is the whole image is smoother. There's just no trace of pixels. On my screen, with a 720p projector, I could easily make out pixels. With a 1080p projector, if I leaned forward, I could just barely make them out. No chance with that with 4K. It's just a smooth image corner to corner.

Ultimately, however, resolution is still one of the least important aspects to the overall performance of any display, including projectors. Contrast ratio, brightness, color accuracy, even things like how loud the projector is, will all have a far greater effect on your experience. 

Even after living with a 4K projector for several months now, given the choice between a 1080p projector with a great contrast ratio and a 4K projector with a mediocre contrast ratio, I'd take the 1080p projector without hesitation. 

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Got a question for Geoff? First, check out all the other articles he's written on topics like why all HDMI cables are the same, TV resolutions explained, LED LCD vs. OLED and more. Still have a question? Tweet at him @TechWriterGeoff then check out his travel photography on Instagram. He also thinks you should check out his best-selling sci-fi novel and its sequel.