Light output. The X55 is rated at 1200 lumens, which doesn't sound like a lot. However, JVC's home theater projectors have always produced ample video optimized lumens, so the maximum lumen ratings tend to be irrelevant.
Our preferred operating mode, and the projector's default, is Cinema mode. After calibration, Cinema mode produced 820 lumens on our test unit with the lens at its widest angle setting and the lamp at full power.
In most home theaters, 820 lumens is more than enough light. In point of fact, many people will likely want to reduce light output. Switching the lamp to low power mode reduces light output by 33%, bringing our test sample to 551 lumens in Cinema mode. On a 120" diagonal 1.3 gain screen, that works out to almost exactly 16 foot-Lamberts.
However, a lot of people won't be using the maximum wide angle zoom. At the telephoto end of the zoom range, the X55 loses 31% of its light output potential. In other words, Cinema mode would measure 565 lumens with the lamp at full power and 380 lumens with the lamp at low power. The latter is enough for a 100" diagonal 1.3 gain screen at 16.7 fL.
Cinema mode turned out to be our test unit's brightest 2D image mode. The projector's 3D mode does measure higher, at 917 lumens on our test sample, but remember that 3D glasses cut brightness quite a bit -- even a theoretically perfect pair would reduce brightness by 50%. It is not uncommon to see total 3D system efficiency around 20-25% of 2D light output.
Contrast and black level. The X55 has the best black levels we have seen in a projector under $5,000, period. The difference between it and its competitors is not always night and day; projectors are too advanced these days for any huge, show-stopping differences to crop up like that. But when placed side by side with other home theater projectors, the X55's black levels were consistently the deepest, the darkest, and the most natural (thanks to the projector's lack of an automatic iris).
Shadow detail is no slouch, either. The X55 was consistently able to render even the most difficult of shadow details in the deepest darkest corners of images, creating a smooth, natural image that is a pleasure to watch. The depth of the image creates a real sense of three-dimensionality, even watching 2D content.
Color. The X55's default color temperature settings are almost perfect as they are. With zero adjustment, our test sample measured 6530K across the board in Cinema mode, with a slight push towards green in both shadows and highlights. Reducing green bias by two points and green gain by one point gave us a perfect 6500K grayscale curve with no major spikes or flaws.
Please note that the divergence in color temperature at 0 IRE in the above graphs is because the X55's black level is deep enough that our meter has trouble obtaining a valid reading. There is no visible color shift in solid black.
As far as gamut is concerned, the X55 measured close to the Rec. 709 standard though it still can benefit from some fine-tuning. As the X55 has extensive color controls including a full color management system, these adjustments are fairly simple. A qualified custom installer can do this if you don't have the equipment to do it yourself.
Sharpness and detail. Native sharpness on the X55 is more than sufficient to bring out the fine detail found in Blu-ray and HD content. The default sharpness setting is 0, and it should stay in that position; the projector is perfectly sharp without any artificial edge enhancement.
However, one cannot discuss sharpness on the X55 without also discussing the 4K e-shift system, which is designed to increase sharpness and detail clarity by interpolating to 4K. What the system really does is analyze the 1080p signal and interpolate detail, which is similar to how a smart sharpening system works on other home theater projectors. The difference is that, in delivering this interpolated detail, the X55 physically shifts the image to create the overlapping-pixel mosaic that is their claim to 4K resolution. During this upscaling and image overlapping, the system (named MPC in the projector's menus) also applies a number of image processing functions to increase apparent detail.
The results can be fascinating. The e-shift system has a number of presets, ranging from "Film" on the unaggressive side to "HD" on the highly processed side. When watching film or movies, anything above the "Film" setting appeared too aggressive in some instances. Meanwhile, when watching video, the "SD" setting was a good fit. SD applies more processing than Film but less than HD. However, some content wasn't a good match for the SD setting, and some ringing and other artifacts became visible. The SD setting also increased digital noise in certain images.
The 4K e-shift system has some definite benefits, but overdriving it can lead to the same sort of problems one finds when overdriving smart sharpening systems on other projectors. Used in moderation, 4K e-shift has the ability to enhance your picture without making it appear artificial or over-processed.