Film-Tech Forum ARCHIVE: Limited screen size. Should I go CW or CH?

This is topic Limited screen size. Should I go CW or CH? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Alan Gouger (Member # 543) on 12-02-2006, 01:12 PM:

Looking for your advice. I am limited to a screen width of 7 feet wide in a small private screening room dedicated to film only. Normally I would never do anything other then a 235:1 constant height system but my 185:1 titles are so small. Considering film allows me to sit much closer then an electronic display I am considering a constant width screen.
What would you do. Are there more CH die-hards here that would never run anything else other then CH regardless or under the circumstances would most recommend going CW??

Thanks!!

Posted by Dominic Espinosa (Member # 2122) on 12-02-2006, 01:30 PM:

I actually prefer common width myself.
I have no argument as to why, I just like it.

Posted by Mitchell Dvoskin (Member # 751) on 12-02-2006, 02:46 PM:

While I personaly prefer CH, in your case I would go CW. It is silly not to have the biggest picture possible on such a small screen. Just be shure to mask to top/bottom when you run scope.

Posted by Ken McFall (Member # 845) on 12-02-2006, 02:58 PM:

With such small screen size I would go for best of both which is Common Width. However in a 'real' auditorium I would go for picture quality rather than size. There tends to be a trend to push 1:85 too far in some places and the difference in illumination is very marked with scope being too bright compared with 1:85.
If it were my choice I would compromise and go for a mixture of both.... with full side and top/bottom masking.
Common Width plays down the impact of the Wide scope image almost making it inferior even though it has an effectively higher resolution in such a case.

Posted by Dan Lyons (Member # 1454) on 12-02-2006, 04:46 PM:

I have an 8 foot wide screen in my screening room; I do CW. For a screen that small, CW is the way to go. [thumbsup]

Posted by Cameron Glendinning (Member # 3516) on 12-02-2006, 05:07 PM:

another option would (perhaps) be a deep curve common hight screen, a mini cinerama style (perhaps not so deep) so perhaps a 10 ft screen in your 7 foot space. With scope, the image filling more of your peripheral image is very impressive.

Best focus is if you attach a string to the projector so that the screen curve is exact same distance from the lens.

In London I remember working in a cinema that had a 35 ft proscenium with a 50 ft screen curved installed. It was cool

Posted by Alan Gouger (Member # 543) on 12-02-2006, 05:27 PM:

I know this question cannot be answered with a single definitive answer but it doesn't hurt to fish for opinions with hopes someone may point out a reason I may have missed to stay away from CW or offer another option. Looks like CW is winning the vote though.

Cameron, interesting. I remember talking to John Harvey years ago
and he recommended a very deep curved screen saying we would have no trouble focusing with a standard lens. I wonder how deep a curve one could go before getting into trouble. Id love to try this but if I cannot focus it could be a expensive experiment.
Anyone have any experience with this. If I did the string between the projector and screen the curve would not be very deep at all. Maybe 6". John was talking deep, almost half a circle.

Posted by Ron Curran (Member # 3631) on 12-02-2006, 05:38 PM:

I don’t know if Americans – like Australians - are experiencing 57 aspect ratios on their 16 x 9 plasmas but if you watch an ad break with all the various shapes, you will be able to judge which would suit your environment.

Watching a smaller 2.35 image on our 16 x 9 plasma is still more impressive than watching a full-height 1.85 (approx) image.

But I would only do that at home. CW has no business in real cinemas.

Posted by Cameron Glendinning (Member # 3516) on 12-02-2006, 07:19 PM:

Alan, The cinema in london was much much deeper than the string thing, but its a good reference point. You should see the 1.85 aperture plate(like the old cinemascope logo).

The wider the lens (smaller the number) the less the depth of field, the more critical the focus but would result in a naturally deeper curve.

So the longer the throw, the less the curve but is more forgiving with the focus, so a deep curve is also possible, in scope the image will look a little stretched at the edges the deeper the curve, 1.85 would not change much, subtitles might not be paralel with the bottom masking.

Cinerama had a 144 degree screen, so I suggest not quite so deep [Wink]

personally though, when I build my screening room, this is the way I'm going to go. I already have a 24 ft wide common hight screen which I hope to put in a 18-20 ft wide room.

Perhaps some focus tests with a bed sheet and gaffa tape before you commit.

I also think the idea from Ken of all movable masking makes a lot of sense, that way no matter what ratio the screen would be a simiar size.

quote: Ron Curran
But I would only do that at home. CW has no business in real cinemas.

Tend to agree with you on that one Ron

Posted by John Koutsoumis (Member # 1855) on 12-03-2006, 06:43 AM:

Not only am I against CW but I don't like CH either. Each ratio should have it's own height in my opinion. I like just a little gentle raise of the bottom mask or bringing down a top mask for scope. In sense I say gentle as in that it's not all that noticeable but adds a real scope feel to the image. Of course the side masks come out substantially.

A screening room that I work at has different heights (and widths) for the different ratios and I quite like it. The films look as they were meant to.

Posted by Brian Guckian (Member # 1678) on 12-03-2006, 07:45 AM:

The other problem with CW is that the optical axes must all be centred, so co-acting moving top and bottom masking for 'Scope is a must.

But just as important, you need to be able to balance the light levels between 1.85 and 'Scope, so you really need a Stop Ring on the 'Scope lens or some other method to equalise the light levels.

I think the Curved Screen concept, which might allow you to achieve CH, is a good idea and should be fully investigated. I'm not sure about a Deep Curve as that could distort the image and may be very difficult to focus, and indeed to illuminate evenly. Definitely one for careful analysis, especially at very small screen sizes.

Also, is there any way of getting more than 7ft on the width, or is that the widest width physically possible?

Finally, CW v. CH shouldn't be seen as a preference! There are cogent design reasons to always use the latter. Ioan Allen of Dolby did a fine paper on this some years back - essential reading and available from the Dolby website!

[ 12-07-2006, 09:36 AM: Message edited by: Brian Guckian ]

Posted by Alan Gouger (Member # 543) on 12-03-2006, 11:43 AM:

Brian

I just goggled Ioan Allen and looked on Dolby's web site and I am having a hard time finding that Paper. If you have a link please post it. It sounds like an interesting read. Thanks!!

You guys have peaked my interest in a deep curved screen. Im going to do some experiments and see just how deep I can go while maintaining good focus. I have a friend just getting started in the screen manufacturing biz that can make me a curved frame at any radius so this may prove to be a fun project.
I can always resort to hanging a cheap manual pull down screen on the wall if things do not work out.

Posted by Louis Bornwasser (Member # 3063) on 12-03-2006, 12:48 PM:

If you look at the framing of the 2 main formats, you will notice that 2.35 tend not to involve severe closeups. This is not the case with 1.85.

With CH, 1.85 seemds more intimate and 2.35 places that intimacy in the context of the wide open spaces. (Think: John Wayne on his horse on a hill.)

With CW; you get inverted reality in composition; that is why it is so unsuccessful. Louis

Posted by Mark Hajducki (Member # 1732) on 12-03-2006, 04:04 PM:

Dolby paper on screen size and shape

I think having movable masking on all 4 sides would be the best option to give the maximum image size in all formats (you would have to look at the distance the viewer will be from the screen).

If you are likely to screen material that was recorded in 4:3 for TV then being able to increase the height would allow you to have a bigger picture for this as well.

Posted by Brad Miller (Member # 2) on 12-03-2006, 05:26 PM:

4 sided masking is definitely the way to go if you are crunched for space.

As far as curved screens, I've never liked them in the first place...but they will look outright dorky on a screen that small.

Plus with curved screens, you lose the apparent width in the aspect ratio, cause geometric distortion and lower contrast. I have also had far better luck with focus on flat screens.

Curved screens suck.

Posted by Monte L Fullmer (Member # 2797) on 12-03-2006, 06:17 PM:

quote: Brad Miller
Plus with curved screens, you lose the apparent width in the aspect ratio, cause geometric distortion and lower contrast. I have also had far better luck with focus on flat screens.

I tend to agree .. seeing 70mm projected on a large flat screen seems to look better than on a curved screen..as long as the downward machine angle wasn't too steep to notice the apparent keystone affect even with trimmed aperture plates..

Thus, if flat screens have better presentations qualities, then why the whoopla on curved screens in this megaplexes then..?

Yes, my cinemas that I work at and service do have the double masking settings..Thus,I have a nice large (1.85/1) flat masking tabs and a decent sized scope (2.35/1) masking tabs..for all my 18 houses in three locations..

-Monte

Posted by Alan Gouger (Member # 543) on 12-03-2006, 06:27 PM:

Monte

When you say double masking tabs for scope and flat are
you maintaining the same width and bringing in top/bottom masking for scope?

Posted by Monte L Fullmer (Member # 2797) on 12-03-2006, 06:56 PM:

quote: Alan Gouger
When you say double masking tabs for scope and flat are
you maintaining the same width and bringing in top/bottom masking for scope?

No..sorry, if I threw a curved ball on this one.

With the actual screen installed and with all tabs open, the ratio is about 2.00/1 - rather wide ratio, but still using a pretty hefty screen size for each auditorium...

When I use FLAT, the top goes up all the way and the sides move in to give me my 1.85/1 ratio.

When I use SCOPE, the top drops down and the sides open up for my 2.35/1 ratio (now, 2.39/1 with a touch on the motor stop tab adjustment for this recommended anamorphic ratio and aperture retrim by tapping on the brass and refile ..)

I've seen theatres that uses 'scissor' maskings - Being the CW type of screens with both upper and lower tabs moving in together for Scope settings.. this keeps the bulb focus in the middle of the screen no matter what aperture cut is used.

Most common practices with machines that are stationary in their tilt settings for each format is to center the bulb on the screen in the SCOPE aperture and masking settings - to get the most of the light out on the screen in this format.

Thus, with the opening of the flat aperture, it's a shade off horizontal center of screen when filing the aperture out if you put an undercut aperture in the machine, and the bulb focus is a bit off horizontal center of screen as well..

Thus, I'd go along with Brad and the most - get the largest screen possible for your home theatre and do the four masking tab stops. You won't be disappointed

[ 12-04-2006, 05:08 AM: Message edited by: Monte L Fullmer ]

Posted by Alan Gouger (Member # 543) on 12-03-2006, 08:58 PM:

Thanks for the breakdown [Wink]

Posted by Charles Greenlee (Member # 3856) on 12-04-2006, 04:06 AM:

Brad, I know I've asked something on this similar subject but please expand on this for me.

quote: Brad Miller
cause geometric distortion

I would thing that light, being projected radially, would be more geometrically correct on a curved screen. And even more so on a concave.

Posted by Gordon McLeod (Member # 33) on 12-04-2006, 08:56 AM:

I always favour curved screens
If the theatre has the projector centred on the screen with minimal downward angle the geometry should not be an issue
Also in almost all cases the focus is better as almost all the newer lens are designed for curved screens
Also light distribution on a gain screen is far better

Posted by Louis Bornwasser (Member # 3063) on 12-04-2006, 06:22 PM:

The focus should not be an issue unless in a very short throw room, whether or not thr screen is curved. As you approach "infinity" (50+ ft) the amount of refocussing required diminishes. Likewise at very short throws, it becomes more critical.

In the days of severe deep curved screens (Cinerama 70) it was sometimes advisable to introduce a magnecom. This allowed the center part of the picture to focus on a more distant plane. Some of the best 70mm I have ever seen was with a really good lens and magnecom, depite the well-known problems with magnecom. Louis

Posted by Mark Gulbrandsen (Member # 72) on 12-04-2006, 07:03 PM:

You should go for a larger house or add on in the grand screening room style! [Big Grin]

Mark

Posted by Alan Gouger (Member # 543) on 12-04-2006, 09:49 PM:

Mark that will be my next move in a few more years.

Well heres what Ive decided. Im going with a flat Scope screen. I am able to get an 8 foot wide image end to end but its a tight fit.
I dont know if anyone is familiar with the newer fabric weave screen materials. For reference there is a HT screen company called Screen Research that introduced this new fabric material. Im going with something similar from another company. The gain around 1.3, white, with a weave similar to a speaker grill which will allow me to sit closer not perceive the holes and enjoy the speakers behind the screen.
I should have this next week. Ill snap some pictures and post them as this comes together.

Lots of good information in this thread. I appreciate the help. This is the best film forum.

Posted by Cameron Glendinning (Member # 3516) on 12-05-2006, 02:44 AM:

quote:
The focus should not be an issue unless in a very short throw room, whether or not thr screen is curved. As you approach "infinity" (50 ft) the amount of refocusing required diminishes. Likewise at very short throws, it becomes more critical.

This is what I was referring to with the smaller no of the lens. usually the wider the lens, the closer you are to the screen [Big Grin]

quote: Brad Miller
As far as curved screens, I've never liked them in the first place...but they will look outright dorky on a screen that small.

All I can say is "I wish I had Brads screening room" wow

A few years ago my local watering hole started running pub movies via video, they brought in a deep curve screen probably 8 foot wide. I liked it, made video look kind cinematic in quite a large room(it was Ants that I saw so not to hard on the LCD projector)

Having recently seen Cinerama for the first time, (6 weeks ago) I am very biased to curved screens at the moment.

For the English readers, the Cinema I was referring to with the 50 ft screen, its the Bellevue in Edgeware (top of the northern line)

Posted by Frank Angel (Member # 248) on 12-05-2006, 03:57 AM:

Alan, what's that new screen material? Is it competitively priced with standard plastic screens? Can you give us more details plz?

Posted by Alan Gouger (Member # 543) on 12-05-2006, 12:36 PM:

Frank

Most of the HT screen manufactures offer a AT Fabric screen material. One manufacture goes the expense for THX certification for audio with no need for an EQ but the expense of the license is passed on to the end user.. There are companies who do not bother with the certification that offer an AT screen relatively inexpensive. The problems with these screens are lack of gain. Most measure .85
There is a new company with a brighter white that is rated at 1.3 that offers excellent results. The 1.3 will be the material I have ordered.

I am still very interested in a deep curved screen but want to get my room finished and up and running first so going with the flat for now allows me to finish the room. In time I will do some experimenting and find out just how deep of a curve I can go and if my room and throw allow one that is deep enough for that cool wow factor yet maintaining good focus I will invest in having one made.

Posted by Charles Greenlee (Member # 3856) on 12-05-2006, 10:14 PM:

Maybe you can buy the material wide enough to do a curved screen, but somehow roll it around the supports on the sides to take up that extra material until you do go curved. That way you don't have to replace it later.

Posted by Monte L Fullmer (Member # 2797) on 12-06-2006, 12:58 AM:

Either Hurley, or Harkness Hall has a certain make of screen called a 'microperf' screen designed for home theatre usage. Can't remember which ... - Monte

Posted by Gordon McLeod (Member # 33) on 12-06-2006, 09:35 AM:

micro perf is available from MDI and Lesna as well

Posted by Alan Gouger (Member # 543) on 12-06-2006, 10:34 AM:

Monte

The perfs in MP disappear around 6 to 8 feet back depending on your eye sight. The holes in the weave material disappear around a foot or two. In my case because Im working with such a small room I felt the Weave would be the better choice but MP would be an alternative to anyone doing a smaller theater.

Gordon

When you say MDI the first thing that came to mind was that whole sale MCI catalog they send around. Who is MDI ?

Thanks!!

Posted by Gordon McLeod (Member # 33) on 12-06-2006, 11:37 AM:

http://www.mdicinema.com/

http://www.lesna.com/applications.htm

Posted by John Pytlak (Member # 331) on 12-06-2006, 12:53 PM:

Again, if you have a low gain (matte) screen, it should be installed FLAT. If the screen has gain, it should be installed CURVED, with the curve and tilt optimized by ray-tracing (angle of incidence = angle of reflection) to aim the light at the center of the seating area.