What is the Optoma HD91?
It’s pretty hard to cause a stir in the consumer electronics business these days.
Design and Connections
The HD91 uses manual zoom and focus for its lens, which puts the projector at a disadvantage to much of the competition because it precludes the addition of a lens memory feature. The HD91 does however have a basic lens shift that uses two small wheels under the front of the chassis. On either side of the chassis there are air intake and exhaust vents and these are important because keeping the temperature of the LEDs consistent is a key element in image accuracy. The chassis sits on four adjustable feet, which makes for easier table or shelf mounting and the HD91 can also be ceiling mounted using an optional bracket. Interestingly there no controls on the projector itself, so don’t lose the remote!
Setting up the HD91 is very easy, you just need to ensure that it’s positioned correctly in front of the screen and then zoom and focus using the manual rings around the lens and, if necessary, shift using the little wheels under the front. We found that the best Display Mode to select is Reference and then you can set the Contrast and Brightness controls accordingly. In the case of Contrast, you’ll need to move it down a bit to stop the image from clipping but Brightness, Colour and Tint can be left at zero. A Sharpness setting of 8 appeared to be the point at which the image was neither being sharpened nor softened.
We left the Noise Reduction at zero, selected the Film setting for Gamma and left the LED Brightness at 100%. Within the latter option there are also choices for DynamicBlack 1/2/3, which adjusts the contrast of the image dynamically depending on the content. We found that despite the mediocre blacks on the HD91, it was best to leave this feature off to maintain the fidelity of the image. In the PureEngine sub-menu there are three separate features - UltraDetail, PureColour and PureMotion - all of which we left off. In terms of the Colour Temperature we selected D65, the Colour Gamut should be set to HDTV, Colour Space set to Auto and RGB Channel to Normal.
As we suspected, a few clicks on the two-point white balance control and we quickly had the greyscale measuring errors below one, which is essentially perfect. The gamma was still tracking at 2.2 between 20 and 80 IRE but there were still slight dips at 10 and 90 IRE, which seems to be fairly standard for all Optoma's projectors. However overall this is an excellent greyscale performance, with white now measuring at the industry standard of D65. The accurate greyscale filtered over to the colour gamut and thanks to the CMS, we were able to get a very accurate colour performance overall. The only real error outstanding was a slight under-saturation in red at 100% saturation but the HD91 performed well at lower saturation points, although the primary colours were still slightly under-saturated. However this is an excellent performance and shows that after calibration the HD91 can deliver a very accurate image, which means Optoma are clearly implementing the LED light source successfully.
The HD91 performed well in these tests and was able to fully reproduce the SMPTE colour bar tests for both PAL and NTSC, correctly scaling the full 576i and 480i images without any loss of detail or unwanted ringing. The video deinterlacing test was reasonably good, although on the motion adaptive deinterlacing test the projector introduced some jaggies. However it had no problems in resolving all the fine brickwork in the detail tests on both the PAL and NTSC discs. On the film detail test the HD91's performance was also good but in the cadence tests, whilst the projector correctly detected the 3:2 (NTSC - USA/Japan) format, it failed to detect the 2:2 (PAL - European) format. However the projector had no problems displaying mixed film material with scrolling video text and was able to reproduce the text without any shredding or blurring.
The HD91 performed well in the tests using high definition content and with the player set to 1080i, the projector correctly deinterlaced and displayed both the video and film resolution tests and showed good scaling and filtering performance as well as good resolution enhancement. With 1080i material the projector had no difficulties in showing video text overlaid on film based material and also handled 24p content without any problems. The one area where the HD91 did fall down slightly was the Dynamic Range High test showing video levels above reference white (235) up to peak white (255). This test showed that the HD91 was clipping all three primary colours and white, thus losing detail above video level 235. Whilst it would be nice to be able to see all the way up to peak white, it isn't really a problem and certainly wouldn't adversely affect the projector's overall performance.
Optoma HD91 Picture Quality 2D
Well there are two major problems and the first we've already mentioned - it's difficult to build a projector with a LED light source and maintain an accurate image. Optoma certainly appear to have cracked this problem and based on our testing the HD91 was capable of a very accurate image after calibration. The secret is effective cooling of the LEDs and so the fans inside the projector's chassis play an important role. In general we didn't find the fan noise to be an issue but occasionally it was noticeable.
The other problem is the brightness of the LEDs and whilst certainly not dim, the HD91 will struggle to compete with bulb-based projectors putting out 2,000-3,000 lumens. Whether the HD91 will suit you will depend primarily on your viewing environment. In our pitch black review room, the HD91 had plenty of brightness and even after calibration it was still putting out 700-800 lumens and could light up a very big screen. In addition the purity of the colours produced by the LEDs themselves does make the image appear brighter than it actually measures. However if you have a bright room with white walls, then the HD91 might not be the projector for you. Of course the fact that the LEDs don't dim very much means that at least the light output will remain largely the same, unlike a bulb-based projector that could have lost half its brightness after 1,000 hours.
Aside from any concerns over the brightness of the LEDs themselves, the only other issues largely relate to DLP technology and how it's implemented. The HD91 is a single-chip DLP projector but thanks to the LEDs it doesn't use a colour wheel, which means the problems with rainbow artefacts are heavily reduced. However, if you're especially susceptible you might still see them on occasion.
The other problem relates to black levels and shadow detail. Almost every DLP projector we have tested has struggled in terms of delivering decent blacks and the HD91 is no excerption. Optoma claim a contrast ratio of 500,000:1 but that's obviously with some dynamic trickery and in reality you won't get anywhere near that - more like 2,000:1 - although for a projector that isn't too bad. The other issue relates to shadow detail and again, like most other DLP projectors, the HD91 will struggle to reveal subtle shadow details.
OK, now we've got that out of the way, let's get down to how the picture looked with real world content and overall we thought it was excellent. Thanks to the single-chip and the decent lens, the level of clarity and detail was exceptional and as is usually the case with a DLP projector, motion handling was excellent. Images were well rendered and the accurate greyscale and colour gamut delivered some very natural pictures. The uniformity was also good and aside from the previously mentioned black levels, there was nothing to complain about. The HD91 did a great job regardless of the source but Blu-rays in particular look spectacular and our current 'disc du jour' - Pacific Rim - looked very impressive with the HD91. Pictures popped with real vitality and detail, giving the images plenty of impact. Optoma are to be congratulated on what they have managed to achieve at what is a previously unheard of price point.
Optoma HD91 Picture Quality 3D
Optoma HD91 Video Review
- Excellent greyscale and colour accuracy
- Impressive motion handling
- 20,000 hours lifespan for LEDs
- Near instantaneous on/off
- Reference 3D performance
- Excellent calibration controls
- Good build quality and lens array
- Mediocre black levels and shadow detail
- Not as bright as bulb-based projectors
- Very occasional rainbow artefacts
- Failed to detect 2:2 cadence
- Fans can be a little noisy
Optoma HD91 LED Projector Review
We were pleased to see that Optoma include a decent set of calibration features and the HD91 can deliver an extremely accurate greyscale and colour gamut, especially after calibration. The video processing is also generally good, although the failure to correctly detect 2:2 cadence is a disappointment in this day and age. The use of LEDs as a light source delivers a number of benefits, including long life and consistency, and whilst not exactly a light cannon, the HD91 is certainly bright enough for most people's needs. The incidences of rainbows are heavily reduced thanks to the lack of a colour wheel but if you're especially susceptible you might still see them on occasion. The blacks are fairly mediocre but that tends to be the case with all DLP projectors, as does the limited shadow detail. Conversely the motion handling was excellent and the 3D performance was superb, which are both strong points of DLP.
Whilst Optoma's HD91 might not be a total game changer, it's still a remarkable technological achievement on the part of the manufacturer. If you're in the market for a new home cinema projector and you like the idea of one that uses LEDs as a light source, your choice is essentially limited to the Optoma. However even if you hadn't considered a LED projector before, the HD91 still deserves your consideration based purely on its excellent performance.
Contrast/Dynamic Range/Black levels
2D Picture Quality
3D Picture Quality
Ease Of Use
Value For Money
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