Film-Tech Forum ARCHIVE: What causes border shadowing on the screen?

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Posted by Scott Jentsch (Member # 1681) on 02-04-2011, 06:04 PM:

I attended a showing of Tangled with my daughter on Saturday at the Marcus Ridge Cinema in New Berlin, WI, and noticed a problem with the projected image, where there was a shadow that appeared around the entire border of the screen.

I mocked up a photo to show the effect I noticed:

This is the same image without it, for comparison purposes:

As misfortune would have it, I ended up in the same auditorium last night to see 127 Hours. Same problem appeared on that movie as well.

Given the uniformity of the issue, I'm figuring it might have something to do with the aperture plate? Is this a normal shadow that would not be visible if the image were increased in size so that the shadow would fall onto the masking instead?

Something else I noticed last night was that it appeared that a band of the screen was different than the rest. Just left of center, about three feet of screen reflected the light differently, which was quite noticeable in the slow shots of the desert in the movie. Looking at the screen up close after the movie didn't show anything obvious. Any ideas on what caused this?

Posted by Michael Brown (Member # 890) on 02-04-2011, 06:28 PM:

Tandled 2D or 3D? Any idea if it was digital or 35mm?

It it was film then in theory you could have been seeing aperture plate shadow on all 4 sides.

This certainly seems like the most probable. (If it was digital then you wouldn't have had shadow. Even if the picture was undersized the edges would be crisp with a black border, not a shadow)

Posted by Randy Stankey (Member # 64) on 02-04-2011, 07:23 PM:

I might be wrong but, as far as I know, whether the image is projected from a digital projector or a real projector, the borders of the picture can still look feathered (hazy/fuzzy) if the screen masking doesn't come in far enough.

Posted by Michael Brown (Member # 890) on 02-04-2011, 07:39 PM:

How would you get any shadow from digital? [Confused]

The shadow with traditional film projection comes from the distance in the gate between the aperture plate and the film.

Posted by Louis Bornwasser (Member # 3063) on 02-04-2011, 07:50 PM:

Film apertures are permitted to be 6" into the masking. Good luck doing this in practice with the dirty masking.

If you try to keep the picture off of the masking you will get what you describe.

Digital, of course, is perfect! [Eek!]

Louis

Posted by Mike Blakesley (Member # 26) on 02-04-2011, 08:37 PM:

quote: Randy Stankey
I might be wrong but, as far as I know, whether the image is projected from a digital projector or a real projector, the borders of the picture can still look feathered (hazy/fuzzy) if the screen masking doesn't come in far enough.

I can confirm that you are indeed incorrect on this. The edges of the digi-picture are sharp.

The picture described by the O.P. is definitely caused by the aperture plate being just a hair too small, or the masking not coming in far enough.

Posted by Brad Miller (Member # 2) on 02-04-2011, 08:57 PM:

Some people INTENTIONALLY file their apertures like this, using the incorrect logic that the picture should not be on the masking.

The entire PURPOSE of masking is to give a crisp, sharp edge and the "fuzz" or "shadow" from the edge of the aperture is supposed to be covered up by the masking.

What you saw was an improperly setup projector.

Posted by Randy Stankey (Member # 64) on 02-04-2011, 09:29 PM:

My digital projector shows feathering/shadow around the edge of the picture but it's a Christie HD8K, not a digital cinema projector. The effect is less than that of our 35mm projector but it is noticeable. Cinema projectors are probably different.

Still, I believe that the effect seen is due to improper aperture or masking. If, as you all say, this does not happen with digital cinema projectors then I would conclude that the image in question was projected via 35mm.

Posted by Steve Guttag (Member # 268) on 02-04-2011, 09:45 PM:

Oh you vidiots....I can "set up" all of your DCinema projectors to have that EXACT type of shadow show up.

If you have a digital projector and see such a thing occur...call your tech immediately though...it is an indication that your integrating rod is miss-aligned. If you see shadow on only a side or two (not all four) then it is more likely a folding mirror. The problem with a misaligned mirror/integrator is that the DMDs are designed to reflect light...the parts outside of the image area, are not and a misalignment will put excess heat on those parts.

However, an improperly masked image with film projection is the most likely explanation in this case. However, to completely discount the possibility of DCinema because "they don't do that" would be wrong.

-Steve

Posted by Victor Liorentas (Member # 5272) on 02-04-2011, 09:49 PM:

Was the dark fuzz around the image as even as your example photo?
If so it's astonishing how carefully wrong it is!
Usually you see one side,top or bottom showing aperture plate due to sloppy projectionists who don't get it or even see it!
Perhaps it was perfect and a Magna-com lens got zoomed down a tad.

Posted by Sean McKinnon (Member # 612) on 02-04-2011, 10:03 PM:

An incorrectly aligned lamphouse can also cause the issue you describe.

Posted by Paul Linfesty (Member # 214) on 02-04-2011, 11:27 PM:

The original Valley Plaza Cinema in Bakersfield also showed this effect, but as there was the proper slight image on the masking, I always assumed it was being caused by the theatre's flat masking with the screen's slight curvature behind it. Both the top masking (used only for 1.66 and, presumably, 70mm) and side masking as well. They just didn't fallow the curve of the screen.

Posted by Eric Robinson (Member # 2966) on 02-04-2011, 11:45 PM:

And of course, some idiot could have carefully put masking tape on the projection window to keep the image off the masking. I see this done all the time - apparently they think the big huge fuzzy fucking shadow is somehow palatable.

Posted by Joe Redifer (Member # 3) on 02-05-2011, 01:16 AM:

quote: Sean McKinnon
An incorrectly aligned lamphouse can also cause the issue you describe.

I was going to say the same thing.

Posted by Jeremy Weigel (Member # 4208) on 02-05-2011, 10:29 AM:

quote: Eric Robinson
And of course, some idiot could have carefully put masking tape on the projection window to keep the image off the masking. I see this done all the time - apparently they think the big huge fuzzy fucking shadow is somehow palatable.

I've had to this before when someone got "file happy" and way over cut the aperture plate. It was better than having the picture bleed way off on to the white side curtains until a new plate came in.

Posted by Richard P. May (Member # 3598) on 02-06-2011, 11:45 AM:

The lens focal length could be too long for the size screen + throw, causing a smaller image than it should be.
Filing aperture plates out too far would be more likely to start showing edges of the film that aren't intended to be on the screen, such as DTS timecode.

Posted by Brad Miller (Member # 2) on 02-06-2011, 12:57 PM:

Then the proper lens should be ordered or the masking adjusted.

A visible shadow around the screen edge is simply wrong...and here is a great example of a terrible aperture. If you look at the right side, the bottom half, the tech almost got it right. However everywhere else [puke]

Posted by Jeremy Weigel (Member # 4208) on 02-06-2011, 02:33 PM:

I like to place a few pieces of white copy paper on the masking and mark the 6" bleed over limit mark so its easier to tell when I'm getting close to the limit.

The thickness of the plate can also make it difficult to eliminate the shadow completely, before over cutting past the 6" allowance. I like to bevel the back of the opening on Simplex plates to make for a thinner plate at the opening for this reason.

My favorite plates to cut are the Christie's due to the thinness of the aperture. They are much easier to get no shadow with very little bleed on the masking.

Posted by Brad Miller (Member # 2) on 02-06-2011, 03:09 PM:

Christie definitely beats all other projectors hands down in this department. Probably the worst out there is the Kinoton. Cutting the plate diagonally is a must, but that edge must be carefully smoothed out and tested to ensure there is no aperture scratching happening to the film.

Posted by Joe Redifer (Member # 3) on 02-06-2011, 03:13 PM:

Ug. I know what you mean about the Simplex plates. I am not a fan.

Posted by Frank Angel (Member # 248) on 02-06-2011, 06:06 PM:

Nothing is wrong here with the projector, lens or plate, assuming his plate is cut properly to PA35 -- if so, then it's just a matter of adjusting the masking correctly to cover the fuzz, not trying to get a lens to overshoot the masking. Besides, that little bit of fuzz won't be fixed with the next step down FL lens as that would enlarge the picture much more than necessary and the masking would have to be adjusted anyway. Not to mention that it would also screw up his scope image.

Posted by Eric Robinson (Member # 2966) on 02-06-2011, 10:04 PM:

quote: Jeremy Weigel
I like to bevel the back of the opening on Simplex plates

Would it not make more sense to bevel the opening outward (towards the lens) so that the edge closest to the film is sharp and defined?

Posted by Brad Miller (Member # 2) on 02-06-2011, 10:34 PM:

Masking systems should be adjusted to be as close as possible to ideal on PA-35 test film. Then the aperture plates should be filed to the masking, not the test film. This way curved screens and other factors such as off-center projectors and downward tilt are taken into account when filing to produce a pleasing and sharply defined image.

If this wasn't the case and every theater was absolutely perfect with one projector, dead centered and with 0 degree tilt, aperture plates wouldn't be supplied as "undersized" with the intention of filing.

Posted by Joe Redifer (Member # 3) on 02-07-2011, 12:12 AM:

quote: Eric Robinson
Would it not make more sense to bevel the opening outward (towards the lens) so that the edge closest to the film is sharp and defined?

That's what he's saying. The side towards the lamp should be sightly bigger than the side towards the film.

Posted by Eric Robinson (Member # 2966) on 02-07-2011, 12:27 AM:

quote: Joe Redifer
The side towards the lamp should be sightly bigger than the side towards the film.

What you are saying would imply that the aperture plate is between the lamp and the film.

I'm talking about aperture plates which are between the film and the lens, not between the lamp and the film.

Posted by Chase Pickett (Member # 5975) on 02-07-2011, 12:56 AM:

Honestly I think that theater cracked a flat lens, and replaced it with another from an different auditorium with a different throw and/or screen size. Although it could very well be the aperture plate too. I had to do the same thing after a flat lens decided it didn't like it's place in the lens turret. We luckily have schneider flat lenses that offer "a unique variable iris feature" that allows us to widen/shrink the image. Before adjusting anything, after just swapping lenses, the image looked very similar to the one you posted.

Posted by Eric Robinson (Member # 2966) on 02-07-2011, 01:13 AM:

I am not a fan of Magnacom or variable iris lenses. The booth monkeys always seem to change the lens settings (even when locked down) and then the picture looks like ass.

Posted by Chase Pickett (Member # 5975) on 02-07-2011, 01:31 AM:

quote: Eric Robinson
I am not a fan of Magnacom or variable iris lenses. The booth monkeys always seem to change the lens settings (even when locked down) and then the picture looks like ass.

haha I can't agree with you more. The "lock" on the schneider lenses we have are way too easy to turn. I can honestly stick a pen cap in place of a hex key to rotate it. But, we have strong projector heads, and to be honest, I think their lens turrets are garbage because of shadows being caused by the lenses coming out of alignment. Even when closed/opened very very very gently. Plus I swear you unlock the lens, adjust it, then when you go to tighten the locking bolt you will knock the lens out of adjustment again. Needless to say, with those lenses and projector heads, I'm constantly battling shadows.

Posted by Joe Redifer (Member # 3) on 02-07-2011, 02:11 AM:

quote: Eric Robinson
I'm talking about aperture plates which are between the film and the lens, not between the lamp and the film.

What bizarre, non-common Simplexes are you threading?

Posted by Scott Jentsch (Member # 1681) on 02-07-2011, 03:27 PM:

The presentation was film, not digital. Marcus is a chain that desperately needs to replace all of their film equipment with digital, because they seem to have a problem getting jump and weave under control. Those two issues were pretty much missing in screen #11, so I guess I have to choose the lesser of their evils...

I looked back at the booth window, and there was no tape on the glass (that was my first thought).

The effect was pretty close to what I showed in the example. Nearly uniform all the way around the image. Thinking back on it, the amount of shadow was probably greater, but the example is pretty close.

The auditoriums at this location are all over the board. If you look at my Reader Comments for the Marcus Ridge, screen #5 had an alignment issue with Kings Speech on 1/8 and Harry Potter was about right masking-wise on 12/22. I haven't written about Tangled and 127 Hours yet, as I wanted to get some confirmation of what I was seeing before mentioning it.

I usually go to Showtime Cinema in Franklin, which does a better job, but convenience of showtimes and the need to burn some gift card balances has sent me to Ridge more often in the past two months than in the past two years.

Posted by Joe Redifer (Member # 3) on 02-07-2011, 05:28 PM:

If it was uniform on all sides, they could slide the projector back a bit and readjust the tilt. [Wink]

Posted by Eric Robinson (Member # 2966) on 02-08-2011, 11:26 AM:

quote: Eric Robinson
I'm talking about aperture plates which are between the film and the lens, not between the lamp and the film.

Hmmm. I'm not sure what happened to my brain, I was clearly illogical in retrospect...maybe I need to see a shrink.

Sorry for the confusion Joe.