"A typical 100 watt incandescent bulb has a luminous flux of about 1700 lumens"

OMG! What is that quote suppose to mean?

Richard.. have you only done video but never been involved in lighting optics?

Yes.. a 100 watt light bulb can be 1700 lumens when the light is captured by an integrating sphere!!!! However try to get that 1700 lumens through projection system optics and you will be lucky if you end up with 300 lumens.

An NOW.. We are going to talk about lumens:

First: What is the difference between 2.5K, 5K, 10K and 15K lumens?
Answer: Screen size

Second: What is the visual difference when you compare a projected image of the same size from a projector that is twice as bright as another?
Answer: You can see the difference but it does not look "twice as bright"

Third: If you have a background illumination of 1K lumens on a screen which
one will completely overshadow the 1K lumens? 5K, 10K or 15K?
Answer: None of them they are all contaminated

Fourth: What screen has a higher luminous measurement? A 300cm X 400cm
screen at 5K lumens or a 435cm x 580cm at 10K?
Answer: 300cm x 400cm at 5K lumens

Fifth: What produces a more stable light output over life? A xenon lamp
used with a 12K projector or a high pressure mercury used for a 5K
projector?
Answer: High pressure mercury lamps produce a more stable light output over
life. Xenon lamps can be 50% output within 500 hours. High pressure
mercury lamps can be 80% output at 500 hours.

Sixth: What is more expensive to own and operate? A single fixed projector
at 18K lumens or 4 automated DL-1 at 4500 lumens?
Answer: The single fixed projector at 18K lumens.