Projectors

There are four main optical projection technologies in widespread use in the home entertainment projector market. 

DLP

The most widely used is DLP technology. Created by Texas Instruments, DLP shines light onto an array of tiny mirrors mounted on a ‘Digital Mirror Device’ (DMD) control chip, with the mirrors being continually adjusted to adapt how much light is being output for each pixel in an image. DLP projectors can come in single chip or triple chip versions. In single chip models, colour is created by passing the light from the mirrors through a spinning colour wheel, while in (much more expensive) triple chip models, separate DMDs are provided for the red, green and blue colour elements.

DLP is a favourite for home entertainment projectors because it can be very affordable, delivers better light control and therefore better contrast than its most direct LCD rival, and tends to show images that enjoy a smooth, filmic finish free of pixel structure. 

Problems with DLP are that the colour wheel can be noisy in some designs, it may reduce brightness and can cause something called the rainbow effect, where you see stripes of red, blue and green flitting over bright parts of the picture. 

Native 4K resolution DLP projectors involve spending megabucks. That said, DLP can use a system whereby it ‘double flashes’ the mirrors on its DMD to create a 4K-like effect that’s usually quite convincing. In fact, the Consumer Technology Association in the US classifies this technology as true 4K.

Brands that routinely use DLP technology include BenQ, Optoma, Samsung, LG and Sim2.

LCD

LCD projectors deliver their light onto mirrors divided into the three primary colours, with the resulting red, green and blue elements then passing through three separate prisms to get their intensity right before they’re converged using a further final prism for passing out to your screen.

Since they don’t use a colour wheel, LCD projectors tend to deliver more of their light to the screen, they don’t suffer from the rainbow effect, and tend to look a little sharper and less noisy. LCD projectors don’t have to deal with any potential humming or whining noises from the DLP colour wheel, either. 

On the downside, LCD projectors are more prone to revealing visible image structure, tend to need larger bodywork, and typically can’t produce such deep blacks or as much contrast as DLP.

The biggest brand to use LCD technology is Epson.

SXRD and D-ILA

We’ve put these two together as they’re both actually brand-specific sub-groups of a technology called Liquid Crystal on Silicon (LCoS). 

LCoS projectors are effectively hybrids of DLP and LCD projectors, combining reflective technology like DLP with three chips for red, green and blue light as LCD projectors do, as well as crystals to block/permit light that work in a similar way to LCD’s prisms. 

LCoS advantages are that it’s easier for them to deliver higher resolution images than the more affordable LCD and DLP options; that they don’t suffer from any rainbow effect; and that they’re capable of delivering better contrast and black levels than DLP or LCD. 

Disadvantages of LCoS projectors are that they typically have to be significantly larger than LCD or DLP models, tend to be more expensive, and can, without high quality processing to support them, suffer from motion blur.

Sony home entertainment projectors use a proprietary take on LCoS technology called SXRD, while JVC projectors use another proprietary option called D-ILA. Sony’s version is particularly effective at fitting more pixels onto smaller chips, delivering native 4K resolutions way earlier than any home projection rivals, as well as boosting brightness while removing visible image structure. JVC’s version is renowned for delivering class-leading contrast and black levels, and recently joined Sony in offering native 4K resolution on most of its D-ILA projectors.

Lamp or laser?

Projectors can be illuminated in two main ways: by lamps, or by lasers. Lamp projectors tend to be considerably cheaper up front than laser ones, but you will typically have to replace a lamp after every 2000-4000 hours of use (the exact lifespan of a projector lamp varies between projectors and depends on how brightly you run it). Replacement lamps typically start at £200 or so. Lasers, by comparison, last for at least 20,000 hours - basically the full lifetime of the projector.

Lasers also retain more of their performance over their lifespan. It takes lasers around 20,000 hours to lose roughly half of their brightness, while lamps lose a similar amount of brightness in as little as a tenth of that time.

Lasers tend to deliver more brightness, purer colours and more colour volume than lamps. However, they used to struggle more to control their light enough to deliver good, cinematic black levels than lamp projectors. This has started to change over the past couple of years, though, with more and more laser projectors now able to partner their brightness with much better black detail.

There can be tri-laser projectors or single laser projectors, finally, with the former delivering more brightness and colour purity. Though again, tri-laser projectors tend to be more expensive, and can unexpectedly suffer from the rainbow effect.

Throw ratios

The term throw ratio refers to the distance from your screen a projector has to be positioned to create a specific image size. This is critically important when trying to choose the best projector because you need to know that it will give you the size of image you want in your room. The throw ratio information for a projector should include details about the amount of zoom a projector supports, and how this affects the throw ratio. 

Most dealers provide tables on their websites indicating the image size a particular model can give from different throw distances.

Real versus digital zoom

In assessing a projector’s throw ratio potential, be careful to distinguish between optical and digital zoom. Optical zoom refers to how physical adjustments to the lens can help you magnify or shrink the image - which is a good thing. Digital zoom refers to a projector using processing to magnify the information in a picture - a process which usually results in messy, unnatural images that aren’t nice to look at.

Getting a projector with a lot of optical zoom - say 1.5x or more - can make it much easier to set a projector up in a variety of room layouts.

Optical image shift

Some projectors allow you to mechanically shift their images up, down, left and right to help you get them on your screen while keeping the four sides parallel with each other. If a projector doesn’t support this, you may need to use digital keystone correction to get the image rectangular - but digital keystone correction is essentially a digital distortion of the image that can reduce picture quality.

Ultra Short Throw projectors

A relatively new home entertainment projector phenomenon is ultra short throw (UST) technology. These projectors bounce their images around a series of internal magnifying lenses before pushing them out through a slit on their top edge, allowing them to deliver massive pictures even though they sit very close to your wall or screen. 

This approach is appealing because it means you can put the projector on a shelf below your screen, rather than having to accommodate a projector in the middle of the room. In fact, one or two brands have tried to market UST projectors as direct alternatives to TVs. 

Bright UST projectors can retain watchable pictures in bright rooms better than regular projectors too, as their light has a shorter distance to travel.

UST projectors that have powerful speaker systems built into their rear edges (which in UST projector’s case are the edges that actually face into your room) are now appearing.

UST projectors are bigger and bulkier than normal projectors, though, and can struggle with issues such as light ‘hot spots’, black levels, keeping straight edges, and retaining focus into the corners. There’s a lot of innovation at the moment, though, which is seeing widespread improvements in these areas.

Connections

Make sure any projector you buy has the connections you need. Most home entertainment users will want two HDMIs, in particular, while others might want a USB port for multimedia file playback, or a powered USB port for powering a streaming stick. Or maybe also a VGA port for attaching a PC. In short, it’s worth making a list of connections you anticipate you’ll need to check that any projector you buy has them.

Gaming features

If you want a projector for gaming as well as watching TV and movies, look for fast response times (how long a projector takes to render images, usually expressed in milliseconds). Projectors that take more than 25-30ms to render pictures can seriously hinder your gaming skills. Also, if you have one of the latest consoles or PC graphics cards, you may want to look for a projector that supports high frame rates of 120Hz or more.

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