DLP projectors generally have a much deeper video black than LCDs. The difference is often striking so you should definitely be looking at
DLP technology for a start.
That's probably a little overly
broad generalization as there is a range on both types of projectors and even changing the color wheel on
DLP projectors, some projectors come with more than one color wheel, can affect the black
level and contrast. While
DLP projectors typically have had an advantage in black levels and contrast and
LCD projectors an advantage in color rendition, the differences in both cases have significantly decreased as the technologies have improved.
Along the same lines, while you asked about
projector specifications, you also noted that the concern was about when part of the
image is black and other parts brighter. That means the issue is not simply how black or how bright the
projector can be but rather what range it can support at the same time. This means that full on/full off contrast ratios are not directly relevant and
ANSI checkerboard contrast ratios are probably much more applicable. Just FYI, a trick that can be used to increase the published full on/full off contrast ratio values for
DLP projectors is to measure full black with a 'high color' color wheel and then measure full white with a 'high brightness' color wheel or even the color wheel stopped on the white segment. That does reflect the maximum and minimum output levels but you'll never get that contrast ratio in real use. A less devious but similar aspect applies to any ratings for
DLP projectors with multiple color wheel options as one has to be sure that the brightness and contrast values specified are with the same color wheel, it's not really unreasonable to specify the
projector brightness using a 'high brightness' color wheel since that is what someone concerned primarily with brightness would likely use but to specify contrast ratio based on a different color wheel, however the two are not necessarily achievable at simultaneously since they are based on different conditions.
However, the general
point of black levels of different projection technologies actually goes back to my earlier
point that with many more recent projectors and a reasonable
image brightness for the applications noted, one would need to have very low ambient light levels on the
screen for the
projector black
level to be the controlling factor in the
image black
level. Just for reference, some sources I've found suggest 10,000+fc for direct sunlight, 1,000fc for
daylight, 100fc for outdoors on an overcast day, 50-100fc for classrooms, 30-50fc for task lighting, 1fc for twilight, 0.01fc for a full moon and 0.0001fc for starlight (a footcandle is equivalent to a footlambert). You may be able to get those low levels in some indoor situations but it would be very difficult to do in the outdoor urban setting mentioned.