Lots to Love

Lots to Love
Toshiba’s TLP-T701U video projector and document camera
By Kevin M. Kilbride

Summary: An exemplary video projector that would earn five stars were it not hobbled by its less-than-great document camera
Target Users: Presentation professionals
Platforms: Windows and Macintosh

In cooking, it’s just as easy to spoil a dish by adding an ingredient that doesn’t belong as it is by leaving out something that does. That aphorism has a corollary for video projectors, reflected in the $5,929 Toshiba TLP-T701U, which is much better off as the $4,899 TLP-T700U because then it doesn’t include the optional document-imaging camera. Both models are built on a 2,000-ANSI-lumen, XGA-resolution display engine capable of projecting very beautiful images—from anything other than the integrated camera.

The TLP-T700U and TLP-T701U incorporate the same projector; the latter model includes a document-imaging camera.

Admittedly, adding real-time image capture to a projector has a certain theoretical appeal. Who hasn’t wanted to display an impromptu document from time to time? Yet, portable projectors are expected to be somewhat smaller than photocopiers or process cameras, and this requirement significantly complicates matters. The principal stumbling block is document illumination, which must be uniform and cannot induce specular reflections on whatever is illuminated. Toshiba put the document lamp in the only practical location on a portable projector: right next to the camera lens. As you might imagine, this had less-than-flattering consequences for image quality.
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Paper Mate
Paper is not a perfectly diffuse reflector of light. In fact, the paper stocks used in color printing are typically calendered and coated with clay or plastic resins that make them quite shiny. Photographing any reflective object from an angle symmetric to the incidence angle of its dominant light source will result in a virtual image of the illuminating source appearing as a specular highlight on the object, washing out part of the surface with glare. This is exactly what happened to color documents when viewed with the TLP-T701U’s integrated camera. A big white smear of light appeared right smack dab in the middle of the page.

Even laser-printer paper was not immune. Although laser stocks are significantly less specular than coated papers, if lit from an angle close enough to the viewpoint, glare will still appear. To convince yourself of this, just shine a penlight on a sheet of paper from a spot right between your eyes. The distance separating the camera and light on the TLP-T701U was comparable. No adjustment of the camera’s input gain was able to compensate for this phenomenon and make legible the text within the resulting hot spot.

Not surprisingly, the type of document that reproduced best was white text set against a black background on matte paper. Hardly a typical document. You could, of course, attempt to restrict yourself to photographing non-paper objects with the camera, but most such objects are fabricated from materials that are significantly more reflective than paper. To top it all off, the controls for the document camera weren’t even integrated into the projector’s remote control! In light of the prior, only one conclusion can be reached about the camera on the TLP-T701U: Forget about it.

Fortunately, the Toshiba projector fared quite a bit better if you ignored its flawed document camera. The image processing circuitry in the TLP-T701U (and, by inference, the cameraless 700U) was absolutely first-class, producing a phenomenal image quite atypical of portable LCD projectors. Color rendering and gray-scale reproduction were nearly perfect, with no perceptible truncation of highlight or shadow detail. Although total contrast was very high, it did not appear exaggerated and the scale was free from unpleasant non-linearities.

Pretty Picture
All types of content looked marvelous when displayed on the Toshiba projector: photographs, applications, business graphics, animation, video. It was almost like alchemy. How else to describe a projector that could render eye-popping, fully-saturated animations and business graphics without making flesh tones or subtle photographic pastels look comical? The RGB balance of this projector was peerless.

The T701U’s video-scaling circuitry was especially meritorious. Title sequences from DVD sources that displayed as blurs on other projectors reproduced with razor sharpness on the Toshiba, and exhibited very little dot-crawl. At the other end of the sharpness spectrum, subtle gradients showed no posterization, although the projector’s contrast was high enough that any color aliasing present in the source material itself was made plainly visible.

The black-level frame projected by the TLP-T701U was dark and extremely uniform, with no light leakage beyond the image rectangle. Unlike projectors that frame their source lamps with tiny exit apertures, Toshiba opted for the more elegant approach of gathering and collimating light from the projector’s tiny 165-watt lamp using a cellular lens nearly the same size as the lamp’s reflector—a strategy which not only boosted power efficiency, but probably contributed significantly to the evident image quality by reducing contrast-killing flare at the LCD panel.

At the other end of the optical path, a fast f/1.9-2.3 projection lens focused with smooth precision, rendering pinpoint pixels throughout its rather narrow 1.25:1 zoom range. A sizable lens shift helped to alleviate keystone problems; digital keystone correction was available to eliminate whatever distortion remained. Although I generally do not like digital geometry circuits, I will make an exception for this projector, since its low black level and flawless scaling circuitry combined to make the compensation much less noticeable—even in very dark display environments. As a nice touch, the projector even had a sensor to determine the extension of its front foot, enabling it to dial in the correct keystone compensation automatically.

Toshiba positioned the exhaust fan on the T701U up front, right next to the projection lens. Given the rather short throw of the lens, a front-facing fan proved to be well-considered, as it is unlikely any member of the audience will ever be positioned in front of this machine. Noise from the fan will, therefore, be projected away from, instead of toward, the audience. The TLP-T701U was not exactly silent, but its noise level was comparable to that of other projectors in its brightness class, even from the front. A selectable low-power projection mode attenuated fan noise considerably, although most of the evaluations I performed were done in full-power mode.

Source: AVVMMP

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