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Hitachi PJ-TX100 Three-Panel 16:9 LCD Digital Projector

Part II

August, 2004

John E. Johnson, Jr. and Steve Smallcombe

 

Measurements and Viewing

Measurements were accomplished using the component video output of a Denon 5900 DVD Player, in progressive scan mode. From my experiences with DVI so far, I am not satisfied that DVI outputs from consumer sources are all doing what they are supposed to do yet in terms of standards. In future reviews, we will use test signals from the DVI output of an Accupel Color Signal Generator, which is an industry standard.

From our tests so far, HDMI sources appear to be compatible with DVI inputs on projectors such as the PJ-TX100. You need an HDMI to DVI converter cable for this purpose.

User Level Adjustments

Using the component video input to the TX100, the Black Bars test on Avia indicated the proper brightness level to be –17, and the moving white bars indicated an optimum contrast setting of +7.

The Color Decoder test indicated no significant push of any color – a very good result.

When Secrets evaluates a projector, we not only look at images, but also measure the color balance of the projector at various light intensity levels and determine the quality of what is called "Grayscale Tracking". The idea is that black, white, and all shades of gray, should have the correct ratio of the three primary colors  - Red, Green, and Blue - used in video projection. You can read more about the testing method used for projector reviews at http://www.smartavtweaks.com.

Preliminary tests using the Dynamic Mode showed a high level of brightness, measuring 66 ft L with a 68 inch wide image, which corresponds to 1193 ANSI lumens, essentially achieving Hitachi’s specification. 66 ft L however is considerably brighter than is considered ideal for Home Theater usage, so a reduction in the light level using the Iris control was needed (about 1/3 less than full brightness) to produce a comfortable image in a darkened room.

The measured contrast ratio was just above 600:1 under these circumstances. However, as can be seen in the Color Intensity graph above (before tweaking), red was significantly blown out at the higher IRE levels. At the mid IRE levels, however the overall color balance was actually quite close to the ideal.

Using the menu system to deselect the Dynamic Mode and to select a Color Temperature of 6500 produced more accurate grayscale tracking at the high IRE levels, shown above, as red was no longer blown out. In this mode however the brightness dropped to 38 ft L at the screen (still very bright) with a contrast ratio of 384:1.

While the color intensity graphs shown above are useful for looking at the color balance and tracking of red, green, and blue at the higher IRE levels, low IRE level performance, and color balance in general, are better characterized with a Color Balance graph where the ratio of the various colors are plotted. In the graph above, we can see that the color balance for the TX100 is very close to D65 at the highest IRE levels, but varies significantly at the lowest levels, with too little red and too much blue at IRE 0 (black). This blue to cyan tint for black was visible when viewing dark scenes using these default settings.

Gamma Tracking

Gamma Tracking is a measure of how the light output of the projector responds to the input signal. If the projector's gamma tracking is off, then details in the image will either be lost, or the image may look flat and have little contrast. The Gamma Tracking graph will show the combined light intensity at the various IRE levels relative to a theoretical level. If the projector is accurately producing the intended light intensity level as a function of input or IRE level, all values should be close to 1 in the gamma tracking graph.

In the Gamma Tracking graph above we can see that the TX100 has accurate gamma tracking that is well described with an overall gamma of 2.25. As a result of this truly excellent performance, shadow details, highlights, and the overall “feel’ of the movie should be quite close to what the director intended.

After CC Filter Tweaking

As with most LCD projectors, the TX100 was weak in red at the highest IRE levels, when pushed to the limit, and at IRE 0 because of light leakage through the LCD panels. Therefore, this projector is a perfect candidate for tweaking with a red CC filter. By using a red CC filter we can not only help balance color levels at the high IRE levels without losing contrast ratio, but the red filter can also compensate for the low red level at IRE 0, thus improving grayscale tracking and color balance in that critical area as well. You can read more on how CC filters be used to improve a projector at http://www.smartavtweaks.com/CCfilters.html.

With the addition of a CC40R filter, and adjusting the color balance using the red. blue, and green level controls in the user menu, we were able to achieve not only excellent grayscale tracking, including improvements at the low IRE levels, but also restore the contrast ratio to 600:1. The measured brightness at the screen was now 26 ft L, still a very nice bright image, more than twice as bright as the reference projectors used by either author (but that may change!). Depending on the screen gain, ambient lighting, and viewer preference, one may still choose to use the iris control to bring the image brightness and black levels down at bit. Although there is still a bit too much blue at the lowest IRE levels, the black level and its coloration were greatly improved relative to the projector without the CC filter.

Frankly, for me (Steve), the TX100 was a delight to tweak. All the necessary controls were in the user menu, and the controls were well behaved, e.g., all colors tracked the same gamma, and gamma tracking did not change with gain levels, right up to the point where the color maxed out. This really simplifies the tweaking process, both in terms of the number of controls that need to be tweaked, and/or the number of measurement runs needed to achieve a satisfactory result.

Furthermore, there was plenty of brightness to work with, meaning that a stronger filter could be used if desired, with less need to compromise in an attempt to preserve light levels.

Viewing

Because of the excellent brightness and contrast, the Hitach PJ-TX100 is the best LCD projector we have ever tested. The iris control makes it simple to bring down the brightness if desired, and the lens shift controls are a delight in aligning the image on the screen regardless of where the projector is sitting.

The Screen Door Effect (SDE) is noticeable, but that is the case with all LCD projectors. On the plus side, this also indicates a sharp lens. On a 72" wide screen, we could not see the SDE when sitting any farther away than about 5 feet.

We did notice an issue in motion adaptive capabilities, with a bit of combing on moving heads in stationary backgrounds, in Film Mode, using interlaced input. However, the standard now is to use progressive scan input from DVD players, so just set your player to progressive, and this issue disappears.

Conclusions

Hitach has a real winner here in the PJ-TX100 LCD projector. It is nicely priced, bright, contrasty, easy to tweak, and has every feature you could possibly want. Highly recommended!

 

 - John E. Johnson Jr. and Steve Smallcombe -

 

© Copyright 2004 Secrets of Home Theater & High Fidelity

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