In this second image below (again, Mitsubishi HC3000 on the left), black levels and possibly gamma, and contast come into play. Please note the chair in the background, left of center, and also the trim on the walls. In this small, slightly overexposed image you can make out a little difference, but if you click on the image you will bring up a larger one, that is also a little more overexposed. There you should not have a problem spotting differences. The horizontal trim on the walls is more distinct and overall, a bit more contrasty. You can see the brighter black levels in the letter box area on the Optoma. Again the Optoma is the brighter of the two projectors, but not enough to have that much lighter a gray where black should be.
Lastly, you can note some other differences between the two projectors. Look at the greenish drape. The Optoma HD72 offers up a more saturated, richer color. Please note, on all side-by-side comparisons with the HD72, due to the way I had to set up, the right most side of the HD72 image is cut off. (Just in case you were wondering!)
For our last pair of images, we explore shadow detail in this frame from Lord of the Rings. The first image is normally exposed, and the following one overexposed so that you can see the level of detail in the dark areas on the left and bottom. You will find this same frame on most reviews done this year.
Fortunately the exposures are very similar, although the HC3000 seems to be just a touch more overexposed. There are subtle other differences, but you can see in the dark areas, especially in the lower right, that they are very close, even if the more expensive HD7100 has a slight edge. I would say that the Mitsubishi HC3000 comes closer to the Optoma HD7100 than the less expensive HD72, in this regard.
HC-3000 Overall Image Quality
Below are a number of images covering a wide range of scenes:
More HD-DVD - from the sci-fi movie Serendipity (hey, there just aren't many HD-DVDs to choose from yet)! The production quality on this HD-DVD seems to be pretty good from a color handling standpoint.