Dirty glass, dull bulb

Well, that was disappointing. This evening I went to see Sherlock Holmes: A Game of Shadows at the local cinema. The movie was okay, but I fear that I failed to enjoy it because I was totally distracted by the horrible picture quality.

Now my local cinema is Limelight at Tuggeranong. This was a new startup a few years ago which took over the closed-down multiplex in the shopping centre, put in digital projectors, gave the place a bit of a brushover, and reopened selling movie tickets at much lower prices.

I’ve been impressed when I’ve been there previously. The black levels haven’t been up to the quality of a modern home theatre projector, but certainly adequate, while colours have been rich and engaging.

So what was going on in Cinema 3 tonight at the 8:20pm showing?

When they were running trailers, I was wishing that they’d turn down the house lights, because they were washing out the picture quite significantly. Then they turned down the house lights as the feature began. I couldn’t believe it. Totally washed out. Colours pallid. Contrast absolutely terrible. I don’t think I’ve seen a picture as low in contrast as this since Panasonic introduced the dynamic iris back around 2003!

I was hoping that perhaps this was something to do with the movie’s prologue, but no it continued throughout the movie. I would have guessed a contrast ratio of maybe 500:1. Not only were the blacks at best a dull grey, the bright parts weren’t especially bright. There’s a scene when some of the characters are chugging across the waters on a clear day in a paddle steamer. Dull, dull, dull!

So instead of being drawn into the picture, I’m wondering how a digital projector can lose contrast. As the lamp reaches the end of its life it dulls, but then the blacks should deepen commensurately.

And there were inconsistencies. When we got to a darker section of the movie, in those scenes where almost everything was dark, then the black levels didn’t actually look too bad. That’s not the behaviour you expect from a projector (or any other display) with a poor contrast ratio, unless it has a particularly aggressive dynamic iris. Which I don’t think cinema projectors have. If light is leaking through the LCD panels or whatever, it becomes even more obvious in dark scenes.

So what was going on?

I had a guess, but waited until the credits started to roll before checking it out so as not to irritate those behind me.

The first few credits of this movie are presented in a fancy script on a lightly coloured screen. When I turned back and looked at the projection booth, this was glowing brightly … on the glass of the booth, through which the projected image must pass.

The ideal glass would capture no part of the light. All would pass through unhindered to the screen for maximum brightness. This glass captured quite a bit of the light. Probably only a couple of per cent of it, to be fair, but the image was clear on the glass. A moment later when the normal scrolling white text on black background credits commenced, the text was obvious on this bit of glass (although, obviously, of quite soft focus).

So here’s my theory: the glass was dirty, and the lamp was dull, perhaps due to nearing the end of its life. I say the lamp was dull because I doubt that the glass — dirty or dusty though it may be — would itself be sufficient to reduce the overall brightness of the image.

But the dirty/dusty glass did, in my theory, far more damage. What it did, I think, was scatter part of the light.

Whenever there was a bright image, there was plenty of light to scatter into the darker objects on the screen (all the men wore dark suits). When there was a dark scene, there was nowhere near as much light being projected through the glass to scatter, so they looked surprisingly good.

So bright scenes looked washed out — including with pallid colours.

So that’s my theory. Next week I shall put that to the cinema proprietors and see what they think.

Now, I’m going to finish watching a movie on a large LCD/LED TV, and marvel at the rich colours and dark blacks.

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