Xenon lamps in movie projectors, be they digital or film should not be operated below 80% of their max ratings. Doing so will shorten their life. The cost of replacing a xenon lamp, $1,000 and up, is far more expensive than the cost of the savings in electricity. Further, xenons can and occasionally do fail explosively, taking out the reflector, damaging film or the inside of the projector. In a digital projector, the cost of a new light engine is a significant fraction of the cost of a new projector.

The reason why movies are dim is twofold:
First digital projectors project dimmer pictures. The standard brightness for 35mm. film projection is 16 ftL or 54 cd/m2. The standard for digital is 14 ftL or 47 cd/m2. That's nearly 15% lower. That's the standard. Many theaters do not meet those standards.
The second reason theaters are dim is because they don't replace their lamps as often as often as they should. The warranty lifespan on the average xenon lamp is between 1,000 and 2,000 hours. If a lamp fails under warranty, you get a prorated refund toward the cost of a new lamp. If the lamp explodes while it is under warranty, through no fault of your own, the company will often pay part or all of the cost of repair. Most theaters burn their xenon lamps for 1.5 or 2 times the warranty life span. That is quite reasonable to do. It saves money on the cost of replacing lamps without undue risk. However, if you burn your lamps much longer than that, two things happen: the risk of failure/explosion increases and the lamps lose brightness. Still theater managers try to cut costs by burning their lamps beyond reasonable limits. That's probably the biggest reason why movies in theaters are dim!

When I was a field service tech for one of the largest theater chains in the country, I was regularly called to theaters to solve problems with dim pictures, often because of numerous customer complaints. 90% of the time, replacing the lamp solved the problem. I regularly replaced lamps that were 3,000 hours old or longer. On occasion, I found lamps that had been running for 6,000 or 7,000 hours! The glass envelopes were BLACK!

No, it wasn't supposed to be my job to change lamps. That's supposed to be a job for theater personnel. I was responsible for maintenance, upkeep and repair for 100 screens in 10 or12 theaters spread out over five states. My job was to train people to change lamps, not necessarily to do it all myself. Many theater personnel are either lazy, inept or think they can save money by being cheap.

Those are the real reasons why movie theaters have dim pictures. That's also the reason why may attitude sometimes appears to be so stubborn. I was paid to be an asshole. Some say I play the part well. (I resemble that remark! )

When there is a customer complaint, that presents problems for theater management. They often give rain checks or passes for free movies but are usually hesitant to give refunds. The movie distributors in Hollywood take as much as 80% or 90% of theaters' box office revenue. That figure is based on ticket sales. They don't care if you gave refunds or not. Theaters still have to pay. A theater manager who gives a refund is losing money.

I now operate a single screen, special venue style theater, similar to IMAX. I am solely in charge all phases of daily operation from box office to concessions to operating the equipment. I try very hard to do things right and to make the best presentation possible but, yes, I still make mistakes.

If I got a complaint from a customer like Alan, I would do everything I can to fix it. If the guy was as knowledgeable as him and if I had time, I'd likely give him a quick tour of the booth. Unfortunately, I could not give a refund unless the movie was interrupted or did not play but a rain check or pass isn't out of the question.

Most people who have concerns are usually happy with that and, maybe, some free popcorn.