What is the application? Is it going to be used primarily
in one location or travel a lot? How large an
image? What is the environment (ambient lighting,
etc.)? What projection
screen surface?
While people focus on lumens output and contrast ratio, these can be almost irrelevant in some applications, for example if you have higher ambient light levels on the
screen then the
projector contrast ratio may not really matter. And differences in projection surfaces, their '
gain', can double or halve the
image brightness so a lower output
projector with a higher
gain screen might appear brighter than a higher output
projector with a low
gain screen. On the other
hand, factors such as
zoom range,
keystone correction, noise levels,
etc. are factors that may be relevant but are often overlooked. These can affect the usability of the
projector such as where it can be placed, whether the operation is intrusive and so on.
The application can also be a factor as the warranties for some projectors aimed at the home
theatre market exclude any commercial or industrial use, in
effect anything other than consumer/residential use. You might also look at how repairs or replacement is handled, do you pay to ship it to a service center and wait for some unknown period or do they provide a replacement or gurantee a turn around time?