What would cause the image to be slightly darker on one side?

[Geoff Jones]

I saw The Northman in the "Big Show" auditorium at the Alamo Drafthouse in Westminster, CO.

The left half of the image was slightly darker than the right, with a razor-sharp division between the two sides, straight down the center.

What causes this? Has the projector gone bad? Is there a setting they can adjust?

I would imagine it might not be noticeable for some titles but The Northman had a lot of very dark scenes...

[Mark Gulbrandsen]

It could be one of q dozen things, but most likely the lamp alignment was not set, or at least not correctly

[Jim Cassedy]

Q > "What would cause the image to be slightly darker on one side?"
A> This usually happens when it is lighter on the other side.

<sorry, but I just couldn't help myself>

[William Kucharski]

I suspect that screen uses two projectors side by side for increased brightness, and one side isn't calibrated properly.

I hate to say it, but I have actually stopped going to that Alamo Drafthouse.

Sloan's Lake gets presentation right, every time, in part because Alamo sends trainees there and in part because their manager actually, truly cares about presentation.

But not only does Westminster have occasional issues like this, they play most of their films at a much lower volume than they should or than Littleton or Sloan's Lake do.

[Marco Giustini]

it could be a high gain screen, too much lens shift being used or lamp alignment. But none of those would give you a razor-sharp division between the bright and dim side.
A dual projectors setup should overlay one on top of each other for increased brightness hence that would not explain the razor-sharp separation either.

Unless with "razor-sharp" you mean that the difference was pretty obvious starting from the middle, then it could be any of the above I guess.

[Leo Enticknap]

I've only ever come across one known issue that can cause a vertical "razor sharp" division of this image, and it specifically affected two models of NEC Series 1 projector (the NC800 and the NC2500) - see attached.

But I doubt if Alamo Drafthouse is using projectors that old (and, AFAIK, the chain is entirely Sony or Barco - no NEC), and in any case, this bug would only explain the colors looking wrong on one side, not a dimmer picture but with the colors appearing OK.

[Jim Cassedy]

As someone else may have mentioned, when two projectors are used, the images are usually
overlapped, not placed side-by-side. I'm not even sure you could "split" an image into two halves
under the DCI specifications and with the usual equipment available.
I saw something like this at an old theater once where the problem was actually a light lead from
back stage. A combination of an old firewall and the speaker bafflling slightly washed out the left
1/4 or a screen. The way the shadow (or actually the light) hit the screen made quite a distinct line.
In their case, the problem was only visible for a few hours in the late afternoon when the sun hit
a certain position in the sky and came through an old vent backstage that the louvers had fallen
off of and bounced off the back wall towards the screen. They did finally fix it.

[Marcel Birgelen]

I suspect that screen uses two projectors side by side for increased brightness, and one side isn't calibrated properly.

I highly doubt that, because I know of no current DCI setup that does that. Theoretically, the most recent iterations of Christie projectors should be able to do this, but still, I doubt anybody would be using image blending for a normal DCI setup. It would also be a waste of brightness, because I see no way you could use the maximum of your imager this way, other than with anamorphic lenses.

If they're using a double projector setup, usually the images from both projectors are configured to overlap each other.

Another maybe, why one side may seem darker than the other: If they're using Sony projectors, maybe their gamma and uniformity recalibration is overdue, but that wouldn't give a razor-sharp division, more a blobby inconsistency on screen of brightness and/or color.

I've also seen similar problems with projectors that are placed way to the left or right and are using maximum lens-shift to compensate. In this case, one side is brighter than the other and both edges are most likely a bit out of focus.

[Ioannis Syrogiannis]

Is there to check what was finally it?
By the description (that "razor-sharp" adjective) I would look towards the projection port to see if there is something out of the ordinary there.

As for imaginary scenarios, one can always have two stacked projectors and mask half the screen on each of them. There are better ways to waste money, but it's not as bad as doing war.

[Aaron Tucker]

Razor sharp image problems on Sonys are often a video path problem as the image is carried separately on 4 quadrants all the way to the 4 sxrd ribbon cables per chip.

[Sean McKinnon]

Probably a high gain screen and you were sitting off axis.

[Peter Mork]

Incidentally, you always should point out these problems to the theater. If sound is too low, chronically - tell someone. If you don't, nobody else will!

And do it while the problem is occurring, not after suffering through a show, grumbling about bad presentation. If something can be done, - too loud, too soft, soft focus, whatever - they can fix it (we hope). Your date can always fill you in on the part you missed. (Yelling "Focus!" in the theater won't work.)

Now, this brightness issue is weird; I can only surmise there's a failure of some sort like the kind that Aaron suggested; obviously not fixable on the fly but they need to be aware that you noticed, in case they are inclined to just let it go.

[Geoff Jones]

Probably a high gain screen and you were sitting off axis.

My daughter and I were sitting in these two seats. We both saw it. I've never seen this problem before, and this is where I normally sit.
Northman seats.png

Incidentally, you always should point out these problems to the theater...And do it while the problem is occurring, not after suffering through a show, grumbling about bad presentation. If something can be done, - too loud, too soft, soft focus, whatever - they can fix it (we hope).

LoL - Thank you for a chuckle this morning! The idea that the employees of a theater chain would do anything to fix presentation issues these days is hilarious!

(I wrote a review on Google. The best thing moviegoers can do these days is warn other moviegoers so they can just wait and watch at home.)

[Leo Enticknap]

In defense of Alamo Drafthouse, we have a service contract on one of their sites, and my personal experience of working that contract is that the site staff care about, and are proactive about maintaining, technical presentation quality. I am frequently asked to check out illumination levels, audio channel levels, suspected blown speaker drivers (usually turns out to be a false alarm), and other presentation issues. Usually these are things that the site staff catch themselves, but sometimes it's in response to customer feedback. Unless it's something serious enough that a significant number of customers would likely complain (e.g. the entire center channel goes out), I wouldn't usually be called out for a minor observation (though I would check things out via Teamviewer to the TMS straightaway if doing that might reveal anything), but it would certainly go on the snag list to be looked at the next time I'm on site either for planned maintenance, or to address a screen down fault. Another ADH location I helped to install and frequently answer snag queries from clearly stays on top of presentation issues, too: if they didn't, they wouldn't query the snags.

I can't comment on the other big chains, as I don't do any on site service for them regularly.

[Carsten Kurz]

Although one should normally refrain from using a cell phone in cinema, it is probably a good idea to take pictures of visual issues and show/forward them to the manager. A picture is always better than a description, especially when your first contact is an usher.