Optoma HD91 Plus review

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  • Beautiful, cinematic picture quality
  • No need to change lamps
  • Runs very quietly
  • Slow dynamic contrast system
  • Expensive
  • Slightly high input lag

Key Features: DLP projector with LED lighting; Full HD native resolution; 20,000-hour claimed lamp life; PureEngine processing system; 1.9x optical zoom.

What is the Optoma HD91+?

As its name suggests, the HD91+ is an improved version of 2014’s HD91 projector. It keeps the key LED DLP lighting system that made the HD91 so unique for the sub-£5,000/$7,500 projection market, but delivers enhancements to its predecessor’s brightness and contrast. But do the changes do enough to elevate the HD91+ from the HD91’s “good” level to excellent?

Design and Features

The HD91+ looks identical to the HD91. This is no bad thing: Its elongated shape, liberal use of angles, curved bodywork and large, centrally mounted lens make it more attractive than most projectors on the market. It even manages to inject a dash of colour in the form of a red ring around the lens.

It’s promising to note, too, that the bodywork incorporates what appear to be large venting “wings”. Experience suggests these will prove helpful in keeping a lid on the projector’s running noise.

Optoma HD91+

Connectivity is fairly strong. The two HDMIs are built to the HDMI 1.4 spec; this is a Full HD projector rather than a UHD one. There are two 12V trigger outputs for driving, say, motorised screens and curtains, plus a component video input.

You’ll also find a RS-232 for integrating the projector into a wider home-entertainment system, a USB port for applying potential firmware updates, and a jack for attaching an optional extra 3D transmitter.

The HD91+’s unique selling point is its DLP LED lighting system. While normal UHP projection lamps tend to last between 2,000 and 4,000 hours, the LED lighting in the HD91 Plus is rated at a mammoth 20,000 hours. That’s long enough to watch 10,000 two-hour films, and effectively means that you’ll never need to change the bulb throughout the projector’s working life.

This isn’t the only benefit of LED lighting. It should also enable you to continue watching the HD91+ for every one of those 20,000 hours with a minimal loss in picture quality. Traditional lamps, by comparison, lose brightness and colour response quite dramatically in the course of their operating lives.

LED lamps should also deliver more stable colours than normal lamps. In addition, since they’re much easier to keep cool than normal lamps, turning the HD91+ on and off is pretty much an instant affair, with no warm up/warm down process required. The relative heat efficiency of LED lighting should also help it run more quietly than rivals.

The HD91+ boasts a light output of 1,300 lumens and a contrast ratio of 600,000:1, versus the 1,000 lumens and 500,000:1 of the original HD91. These represent surprisingly large on-paper improvements for a projector that adds only a “+” sign to the name of its predecessor, and they immediately raise hopes of a significant performance boost.

Optoma HD91+

The final noteworthy features of the HD91+ is its PureEngine video-processing engine, which includes tools for enhancing motion, colour and sharpness. It also offers a huge suite of picture setup tools that mean the projector is able to support a professional installation by a trained Imaging Science Foundation (ISF) calibrator.


The original HD91 was a tricky beast from which to get the best; I certainly struggled to find an out-of-the-box setting that I liked. Fortunately, perhaps because of its brightness and contrast improvements, the HD91+ delivers far better instant results – although the comprehensive nature of its adjustments is nonetheless welcome.

For many users the Cinema or, more likely, Film picture presets will be the best starting point, although there’s also a Reference mode that turns off all the projector’s processing for AV fans wanting the “purest” experience.

Personally, I was surprised to find that I quite liked using the PureEngine system. I generally left Ultra Resolution on and both PureMotion and PureColour on their lowest power setting. The only exception to this was gaming, where you need to turn off as much processing as possible to try to minimise the amount of time it takes the HD91+ to render its images.

I also found it was necessary to use the colour-management tools to reduce a slight infusion of reddish-pink that creeps into very dark scenes. However, by far the most important setting to learn your way round is the Dynamic Black feature.

This adjusts the picture’s luminance continuously based an an analysis of the picture being shown – but, for reasons I’ll get into in the Picture Quality section, I found the Dynamic Black 2 and 3 settings pretty much unusable. As a result, I’d suggest using the Dynamic Black 1 setting, since turning the feature off entirely reduces the projector’s contrast performance to a point where it doesn’t quite hit the spot for a projector costing £3,500/$5,250.

If you find even Dynamic Black 1 uncomfortable, then I’d suggest using the non-dynamic LED Brightness feature set to around 60% for a dark room or around 70-75% if there’s some ambient light with which to compete.

When it comes to the physical side of setting up, the HD91 Plus is pleasingly flexible. It sports a 1.9x optical zoom – more than you customarily get with DLP projectors – and there are simple wheel adjustments for optically shifting the image horizontally or vertically. This means you shouldn’t have to distort the image with digital keystone correction.

Optoma HD91+

Zoom and focus are achieved via simple, reasonably taut rings around the lens. However, the thought did occur to me that a motorised system might have been nice on a £3,500/$5,250 projector.

Picture Quality

My first impressions of the HD91+ in action were a little mixed. On the upside, the impact of the extra lumens and contrast is remarkable. In place of the rather flat, limited contrast images of the original HD91, you now get impressively dynamic pictures that genuinely pop off the screen. This is especially apparent now that there’s a winningly natural and deep black-level response against which bright areas and rich colours are able to juxtapose themselves to great effect.

The only problem is that the HD91+’s most dynamic, engaging results require you to use the Dynamic Black feature. Yet if you use this feature on its most powerful two settings, it causes so much distracting light shifting that it can leave some movie scenes pretty much unwatchable.

Optoma HD91+

The issue seems to be that Optoma’s processing takes way too long to make its luminance adjustments – something Optoma tells me is deliberate, since it wants the system to be considered rather then just reactionary in its calculations about when to shift the light level.

In reality, however, this considered approach just doesn’t work effectively at all for content that contains anything but action. Which is a pity, since the Dynamic Black 2 and 3 settings do deliver easily the most punchy pictures.

Turning off all the Dynamic Black processing and manually selecting an “LED Brightness” value instantly removes all traces of the distracting brightness shifting, but also substantially reduces the image’s contrast. White peaks and bold colours look less punchy, and black picture areas take on a greyer appearance – especially if you push the LED brightness above its 60% level.

Keep the LED brightness set low enough and you can still enjoy very filmic-looking images in a dark room. However, once you’ve experienced the extra dynamics achieved with the Dynamic Black tool engaged, you can’t help but feel a little cheated by having to flatten things out with the manual LED brightness setting.

Fortunately, the day is just about saved by Optoma’s Dynamic Black 1 setting, which tones down the dynamic contrast effect considerably. This means that while you don’t get the deep black levels achieved with the higher settings, you do at least get predominantly stable images that nonetheless contain enough black and colour vibrancy to make them worth £3,500/$5,250.

Also notable is the HD91+’s sharpness and detail. I’d go so far as to say I haven’t seen any other non-4K, sub-£5,000/$7,500 projector deliver pictures with so much precision, texture and clarity. The HD91+ does full justice to the phenomenal amount of detail contained in the Blu-ray of Oblivion – and it does this, moreover, without exaggerating source noise, over-stressing object edges or introducing excessive grittiness into high-detail picture areas. Even if you engage the Ultra Resolution feature.

On occasion there’s evidence of moiré noise over particularly tricky areas of detail, such as checked shirts or patterned ties. But as mentioned, this issue crops up very rarely, and when it does it’s subtle enough not to count as a major problem.

Optoma HD91+

The HD91 Plus also deserves huge credit for its colour performance. Tones look more vibrant than they did on the first HD91, and much more convincingly natural and balanced – at least once you’re rid of the initial slight infusion of pink during dark scenes. The slightly green flavour to skin tones sometimes seen on the HD91 has almost completely gone now, only slipping momentarily back into view during particularly extreme light-level shifts while using the Dynamic Black modes.

It’s great to find, too, that there’s comfortably enough subtlety in the HD91+’s colour handling to keep up with the exceptional detail response, meaning you don’t see any issues with banding, colour blocking or plasticky skin tones.

Add into the mix some excellent motion handling by DLP standards – which can be enhanced with some sources by the lowest power level of Optoma’s surprisingly effective PureMotion processing – and you end up with pictures that are seriously beautiful and always genuinely cinematic.

3D Performance

Here again the HD91+ improves hugely on the efforts of the HD91. The extra brightness allows its 3D images to combat the dimming effect of Optoma’s active shutter 3D glasses much more effectively. This result is 3D pictures that look both more dynamic and more three dimensional, as having more light to play with helps the HD91+ to better render the sort of background details and subtle contrast delineations that help deliver a sense of 3D space, especially during dark scenes.

It’s also excellent to find the HD91+’s 3D images suffering with pretty much zero crosstalk ghosting noise, which helps them look crisp and clean.

Optoma HD91+

Motion can look a little billowy at times, and as with a number of other Optoma projectors I’ve tested, I found I had to activate the 3D Sync Inverter feature before the 3D effect started to look natural, even though I never have to do this with any other brand’s 3D pictures. It’s no great hardship to do this, but it does make me wonder how many people with Optoma projectors have tried and given up watching 3D because of this out-of-the-box setting quirk.

Other Things to Consider

Despite its considerable extra brightness, the HD91+ is a remarkably quiet projector to run. With its lamp running at its low power level, the projector is genuinely whisper quiet. But even if you ramp it up to its highest output levels – and even though noise from the projector’s cooling fans certainly increases – it never sounds intrusive.

The HD91+ is less successful when it comes to input lag. My tests showed that it takes around 63ms to produce images on the screen after receiving them at its inputs. This figure was only achievable with all the projector’s processing turned off, however. Call the PureEngine system into play and input lag balloons to 100ms. This matters to gamers where any input lag measurement higher than 25-30ms can have an impact on your performance with reaction-based games.

Should You Buy an Optoma HD91+

The HD91+’s physical size and image characteristics don’t lend themselves to business or education presentations, so you should see it as a dedicated movie projector. If that fits the bill for you, though, and you’re also able to darken your room for serious movie-viewing sessions, then the HD91+ really is an excellent performer.

Optoma HD91+

In an ideal world it would have been a few hundred pounds cheaper – although, to be fair, the fact that you’ll never have to change its lamps will add up to some considerable savings over the projector’s lifetime.

Gamers, meanwhile, will like the quality of its images, but may be troubled by the HD91+’s slightly high input lag.


The HD91+ is a significant upgrade from the original HD91. So much so that, despite a few residual issues with its dynamic contrast engine, it now combines the cost savings and convenience of its unusual LED light engine with some of the most gorgeously involving movie-friendly pictures in town.

Scores In Detail

2D Image Quality : 9/10
3D Image Quality : 8/10
Design : 9/10
Features : 9/10
Value : 7/10




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