[Todd_zilla]

Hello everyone,


I'm an FP newbie who's waiting on his home to be built. I'm reading a lot about 4:3 versus 16:9 screens and my question is this:


Why can't you just install a really big screen that would be tall enough for 4:3 and wide enough for 16:9 and use movable curtains (similar to electronic masking, I guess) to "frame out" whatever picture you're watching?


My initial concern is that the throw distance of the projector might be different for the two different aspect ratios... is that true? If so, could this be worked around? If not, why couldn't this be done? I plan on using an NEC HT1000 as a projector. All feedback is greatly appreciated.

 

[sushi]

It can be done, and many people do. However, most people choose not to change the throw distance or zoom when changing the aspect ratio. Rather, they install an adjustable vertical and/or horizontal masking system on the screen. For example, if you are planning on the HT1000, you could install a 4:3 screen, with an adjustable vertical masking on the top and bottom of the screen, so that it can double as a screen of 16:9 and above. Da-Lite, Stewart and others make nice electrical masking systems, if your budget permits.

 

[mrwizard]

There are generally 2 approaches to handling the different aspect ratios. The first is to make your screen the same aspect ratio as your projector's (the HT1000 is a 4:3 projector), and then use masking to take up any black borders that will be required to fit the other aspect ratios. This approach also allows you to keep a constant zoom and projector-to-screen distance for all formats. It is the easiest way to do it, especially for a 4:3 projector because you never need side-masking, just top/bottom for 1.85:1 and 2.35:1.


The other approach is to strive for "constant height", or "constant width". Constant height is more common, as it probably more closely matches the intent of the film formats. i.e. "widescreen" formats (1.85:1 and 2.35:1) are "meant" to be just as tall as "normal" 4:3, only wider.... If you go with this approach, you would make your screen match the widest aspect ratio (probably 2.35:1), and then use a combination of side-masking and projector zoom/placement to get the other formats to fit.

(Although I have only mentioned 1.85 and 2.35:1, there are actually many widescreen film formats ranging from 1.77 to 2.4 and higher, but 1.85:1 and 2.35:1 are by far the most common, especially on DVD.)

 

[Todd_zilla]

Thanks for the feedback guys...


So if went for a 16:9 screen with a 110" diagonal, the height would be 54" and the width would be 96"... and the corresponding 4:3 screen size for a 54" height would be 90" diagonal and width would be 72". Those would be the screen sizes if I did not want to mask the top and bottom, correct?


Would the projector be able to transistion from 4:3 to 16:9 at these screen sizes without having to be repositioned?

 

[mrwizard]

You would have to check your projector's zoom range to find the answer to that...


I assume by your numbers that you are interested in "constant height" approach.. If you want that height to be 54" (that's really big, by the way...) then the screen will have to be 127" wide to handle 2.35:1. You will have to use side masking for the others. (4:3 material will be 72", 16:9 material will be 96" wide and 1.85:1 material will be 100". Note that while you won't need top/bottom masking, you of course will need left-right masking for all but the 2.35:1 case.


So your projectors zoom range would have to be able to zoom from 72" through 127" (remember, your 4:3 projector will be working as a "constant width" device...) So... If the max zoom divided by the min zoom is > (127/72)=1.78, you shouldn't have to move the projector. There will probably be a very exact placement required, since you will be using the limits of the zoom range, but I assume you have flexibility there.

 

[sushi]

mrwizard covered it... But keep in mind that the HT1000 has a built-in support to behave as a 4:3 or 16:9 projector. So, if you choose a 16:9 screen as you described, a 4:3 image can be projected with the same height without repositioning or changing the zoom (albeit obviously at a lower pixel resolution). All you need is side masks in this case, in order to go back and forth between 4:3 and 16:9. However, when projecting movies with an aspect ratio greater than 16:9, you will still have "black bars" at the top and bottom of the screen.

 

[Dertah]

Todd_zilla,


I think the best compromise is my setup: a Marquee CRT, a 16X9 (1.78:1) screen (mine is 96x54) and black velvet curtains for masking to 4x3 (1.33:1). I use the LEEZA which makes switching between ratios a snap (one button). I think most scalers have this feature (don't know about digital projectors).


My 4x3 material is smaller but it is still 54 inches tall. Also, I do have black bars on the top and bottom for 2.35:1 material but I find these less distracting then bars on the sides.


If you have the money (oh about $7,000) you can look into the Stewart four way masking system that will mask on the sides and the top and bottom (an expense I chose not to incur).

 

[mrwizard]

sushi... how's that HT1000 built-in support for 4:3 AND 16:9 work? You said it will project both at the same height. Does it use some optical panamophic technique to stretch the width out in 16:9 mode? My projector is a native 16:9 that "supports" 4:3 , but it does this by using only the center portion of the 856x484 lcd panel. Does the HT1000 somehow use all of it's 1024x768 pixels in both 4:3 and 16:9 modes? That seems pretty unique... A nice trick, if it works!


Personally, I think they should make a projector that would fully utilize all its pixel real estate for both 1.85:1 and 2.35:1. I don't really care too much about 4:3 or 16:9. Almost all the movies I've watched in the last year have been either 1.85 or 2.35... and I think a majority have been 2.35...

 

[Todd_zilla]

Mr. Wizard,


Here's the write-up from projector central about the 16:9 display on the HT1000:


"This is a standard 4:3 native format XGA projector, which means it has a pixel matrix of 1024 x 768. It produces a 16:9 image in a pixel matrix of 1024x576, with black bars falling at the top and bottom of the image in the 4:3 display. It can certainly be used as a 16:9 projector with a 16:9 screen, where the black bars fall off the top and bottom of the screen. Many users are concerned with the potential distraction of light spill in the black bars with this type of set up. We found that due to the exceptional black levels, the light spill is about as minimal as it gets on a digital projector."


According to this, you would need top and bottom masking to switch between the varying aspect ratios unless you use the "stretching" technology (which is supposed to be pretty good).


I'm not sure I understand the max zoom/min zoom issue. The specs for the lens are listed at F=2.5-3.7; f=22.4-27.0 mm. I'm not exactly sure what these numbers mean. Please help me make sense of this.


Dertah,


I plan on using "masking" but not the pre-bought, highly-expensive, electronic kind... black velvet fabric with manual curtain adjustments will be fine for me... and won't cost very much at all.

 

[sushi]

mrwizard,


No, what I meant was that the HT1000 can "behave like" a 16:9 projector, by not using the top and bottom 12.5% of pixel realestate (as ProjectorCentral's descriptions above). The point is, it can then display a 4:3 image within this 16:9 boundary.


I agree with you in that it would be interesting if somebody come up with a projector with a built-in adjustable anamorphic optics.

 

[mrwizard]

Oh, I get it. It sounds similar to the way my 16:9 projector "behaves like" a 4:3....


So if the 16:9 display uses 1024x576, and you can display 4:3 within this, then it would only use the center 768x576 pixels, right? I guess it's more convenient, and that reduced resolution is still good enough for most 4:3 sources out there, but I would feel bad about throwing away 46% of my pixels (and lumens) just for that... I would opt for native 4:3 and move the projector closer. Or just avoid 4:3 material altogether! (I actually already pretty much do that!!)


That "adjustable anamorphic optics" idea would probably be prohibitively expensive.


Another idea I have is a "constant height" projector. This would be a projector with a native 2.35:1 panel (say 1128x480), and would "behave like" the other modes in a similar fashion by using sub-areas. i.e. 888x480 for 1.85:1, 853x480 for 16:9, and 640x480 for 4:3. It would automatically select the proper mode based on the signal from the DVD player, and crop/scale the picture portion of the signal to 480 pixels high (with NO black bars) in every case. I think this would actually be doable at a reasonable cost, but I doubt we will ever see anything like it.... Native HDTV-sized panels (1920x1080, like Sony's sxrd) are probably going to dominate future designs, which means we will continue to have to zoom/reposition if we want constant height... That resolution will be awesome, though!


now, what was the original topic?

 

[Uther]

Mrwizard, you lost me on the zooming thing. Let's say I use a WXGA (native 16:9) projector projecting onto a 16:9 screen that is 54" in height. In 16:9 mode, the image is as large as the screen. In 4:3 mode, wouldn't I just get black bars on the sides because now the width is only 72", but the height would still be the same and there would be no need for zooming, right? Going the other way, for 1.85 and 2.35, I would just get bars top and bottom because then the width remains constant.


Please correct me if I am wrong, but I would only need to zoom if I chose to go with a 1.85 or 2.35 AR screen, correct? This leads to my next question, with a 16:9 native projector, is it better to go with a 1.85 AR screen? Most projectors should have no problem zooming (without moving the pj!) from that to 1.77 for 16:9 content, right? Given my premise above, since 4:3 content would be the same height as the 1.77 content due to the projectors panel height and width, the zoom would be the same whether I was going to 1.77 or 1.33 on a 1.85 AR screen, correct?

 

[mrwizard]

Uther...


Sounds like you didn't lose me! You are correct on all account. If you have a 16:9 projector (that can deal with the other aspects) and a 16:9 screen, you should NEVER have to zoom. Just mask out the black bars. The zooming is only required when attempting constant height, which is usually why you'd get a 2.35:1 screen...


A 1.85:1 screen makes a lot of sense (at least to me). You will have to zoom just a little for 16:9 and 4:3, but it will most likey be well within the zoom range of your projector, so at least you won't have to move it. If most of your material is either 1.85 or 2.35:1 (as it seems it is for me), you can leave the zoom set to fill the width, and only need small masks for 2.35:1 (no masks for 1.85:1)

 

[Uther]

Woo hoo, I think I finally understand this stuff then! (And it also sounds like a 1.85 AR screen is a great compromise too).


Thanks MW, Sushi, et al.