Disclaimer: This is not a question about which projector to buy, as this kind of question is usually not useful on SE.I may buy my first projector soon. It will be used primarily for streaming HD videos/movies in a living room, from diverse sources (laptop, BD player, other boxes). It will be mounted to the ceiling (normal middle european height - 220-230cm or so), the maximum area to be filled by the image is about 3m wide, but it is not necessary to actually use that up fully, I believe. Sitting distance is about 3-4m away. It will be used during the day and the night. Obviously I accept a very limited viewing experience during the day. What are the important technical points I need to look at when deciding between different models? Obviously it needs the correct inputs for whatever players I want to attach to it. Then I will likely have to look hard at the cost of the device vs. the cost and frequency of replacing the bulb. And noise may play a role.Is there a industry-wide comparable measure for luminosity? Does image quality differ wildly these days or is it basically sorted? What else is important? 
What should keep in mind while researching a projector to purchase?
projector