Color. While grayscale on the H6510BD can be calibrated to near 6500K, the projector still has some color problems. First and foremost, the projector's color gamut is nowhere near the Rec.709 recommendation. This means that while the relative levels of red, green, and blue in an image may be balanced correctly, the projector has a different idea of what constitutes, for example, "green" than the source material does. Color gamut is notoriously difficult to calibrate without the proper equipment, and it is important that low-cost projectors have accurate gamuts whenever possible as most buyers of the H6510BD will not want to spend the money or time to calibrate the projector properly.
What's more, the H6510BD has low color brightness. Color brightness or Color Light Output (sometimes abbreviated CLO) is a measure of a display's ability to produce colored light. The standard addresses the problem of a projector producing much more white light than colored light, which is helpful in certain circumstances but can be actively harmful in others. Our test unit measured color light output at only 47% of white light output when BrilliantColor is enabled. Disabling BrilliantColor reduces white light output such that white light output (WLO) and CLO are equal, but as you might imagine that kills most of the H6510BD's white light lumens.
You should care about color light output for a few reasons. First of all, a large imbalance between WLO and CLO causes the image to look unbalanced and changes your perception of color. Next to a super-bright white, color tends to look dull, dreary, and undersaturated. When you're trying to produce a well-balanced cinema image, the brightness differential can be detrimental.
No VESA port. Some DLP Link projectors have the ability to switch to IR sync by using an external emitter. Since the H6510BD lacks a VESA port, you're locked into DLP Link for the life of the projector. It also makes it difficult, if not impossible, to connect 3D accessories, as they tend to use the VESA standard. Then again, few of the H6510BD's competitors include a VESA port, either.
Color wheel. With a six-segment RGBCMY color wheel spinning at 7200RPM, the H6510BD has a 2X-speed color wheel. This means those sensitive to rainbows will see them in droves. As there are other projectors around this price range with faster color wheels, the H6510BD could be a poor choice for anyone with a known sensitivity to color separation artifacts.
3D flicker. The Acer H6510BD runs at a 96Hz refresh rate, which is low for a 3D projector. This means that users sensitive to 3D flicker will tend to see more of it on the H6510BD than on a projector with a higher refresh rate. If you plan to watch a lot of 3D content, this could be an important criterion for your decision.
No customization of image presets. The H6510BD has a number of pre-calibrated image modes, but those modes cannot be altered. Instead, when you select an image mode and make an adjustment, the projector pushes your settings over to the User option where you can make further adjustments. As the projector only has one User memory, that means you can only save one group of settings.
This can be problematic depending on how you want to use the projector. For example, color calibrations when BrilliantColor is off are wildly different from color calibrations with BrilliantColor on. BC off looks smoother and more natural, but BC on provides much more white light output. If you use your H6510 in a dual-use capacity as both theater and living room projector, it would be helpful to retain both sets of calibrations without having to manually input them every time.
Brightness uniformity. Our test sample showed noticeable dimming in the corners of the image. The dimmest corner (top left on our projector) was only 65% as bright as the image's center. This is most evident on a solid white screen, but it can manifest when watching film and video as well. It is also possible that this was a problem only on our test sample and other samples will not display this flaw.