RS46/DLA-X35 in a short throw room: would you go constant image width or height? - AVS Forum
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post #1 of 8 Old 04-19-2013, 08:51 AM - Thread Starter
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This is mostly a question for JVC DLA owners out there with lens memory setups.

We're renovating the basement and my home theater is changing rooms.

The new room is almost square and my main concern is it will be a relatively short throw for my JVC DLA-X35 projector.

Here's the beef:

Room dimensions: 370 cm in projector throw axis, 360 cm wide. Black projection wall, dark colours elsewhere, no ambient light other than screen.
Projector: DLA-X35 (note this projector has a motorized lens with 5 user programmable lens memory settings for 5 combinations of a specific focus, zoom, and vertical/horizontal shift)
Throw distance: 312 cm (that is the maximum I can go - it leaves only 10 cm behind the projector to the back wall where the cold air intakes are and the manual specifies 20 cm)
Viewing distance: 308 cm
For what its worth, as we are renovating at this point nothing is built into this space so I can wire in, install, anything I want. Above dimensions are projected internal after drywall and include the standoff distance of the screen surface from the projection wall.


At maximum zoom for a throw of 312 cm the various calculators (JVC, projector central, elite) tell me I can get between 223-229 cm projected image width.

What I am thinking will be best here is a CIW set up and projecting a 220 cm wide image for all aspect ratios. I'll use a masking solution to close down or open up the screen along the vertical dimension.

My feeling is this will work best in my situation because:

This will give me the biggest projected image for all ARs without resorting to an anamorphic lens (2 m2 for 2.4 material and 2.7 m2 for 1.78)
I will certainly not have a problem with too little brightness even at close to maximum zoom - in this dark room if anything I may have to consider a screen gain lower than 1.0
The 5 programmable settings of zoom, focus, and vertical/horizontal shift should allow me to easily switch between 5 main AR projection requirements


I know a majority of people seem to be fans of CIH setups but I think at least 3 factors specific to my case make and the X35 make a CIW setup more appropriate: the lens memory feature of the X35, the short throw, and my desire to have as big and immersive a picture as possible.

I'd appreciate comments to either reassure me it makes more sense for my situation or point out if there is something I am overlooking. For what its worth I don't give much credence to the view that a cinemascope picture should be "bigger" than 1.78 material. I only watch one film at a given sitting anyway, so the argument that there is an "oooh aaah" factor from seeing the masking panels on the sides pull outwards for 2.4 material doesn't sway me. I simply want to project cinema material in the aspect ratio it was filmed in and use all of my projector panels to their full capacity in a relatively short throw room.

Dave M

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post #2 of 8 Old 04-19-2013, 10:57 AM
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Re your last sentence: If you zoom you won't be using your projector panels to their full capacity for all aspect ratios. You would need an A-Lens to do this (I know you aren't getting one, but just raising a point).

I'm not sure if you really mean a CIA (constant image area) set up since you won't be using the lens shift at all in a typical CIW set up. Although you could use it to shift the image down for 2.40:1 content so that you only have one double sized top black bar to mask.

FWIW I have an X35 and a 2.8 metre wide 2.35:1 screen with a 1.5 gain and even at minimum zoom I have enough brightness at 200 hours to still be able to use minimum iris for 16:9 content (approx 100" diagonal) and only -8 for 2.40:1 content (with lens, but in my set up this isn't any brighter than zooming anyway). What I would suggest is that you don't use maximum zoom since I find that the image gets softer as it is zoomed, but this might be due to me being accustomed to the sharper image I get at minimum zoom.

Zooming: Been there, done that, bought the lens...
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post #3 of 8 Old 04-19-2013, 12:59 PM
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Quote:
Originally Posted by dave in gva View Post

This is mostly a question for JVC DLA owners out there with lens memory setups.

We're renovating the basement and my home theater is changing rooms.

The new room is almost square and my main concern is it will be a relatively short throw for my JVC DLA-X35 projector.

Here's the beef:

Room dimensions: 370 cm in projector throw axis, 360 cm wide. Black projection wall, dark colours elsewhere, no ambient light other than screen.
Projector: DLA-X35 (note this projector has a motorized lens with 5 user programmable lens memory settings for 5 combinations of a specific focus, zoom, and vertical/horizontal shift)
Throw distance: 312 cm (that is the maximum I can go - it leaves only 10 cm behind the projector to the back wall where the cold air intakes are and the manual specifies 20 cm)
Viewing distance: 308 cm
For what its worth, as we are renovating at this point nothing is built into this space so I can wire in, install, anything I want. Above dimensions are projected internal after drywall and include the standoff distance of the screen surface from the projection wall.


At maximum zoom for a throw of 312 cm the various calculators (JVC, projector central, elite) tell me I can get between 223-229 cm projected image width.

What I am thinking will be best here is a CIW set up and projecting a 220 cm wide image for all aspect ratios. I'll use a masking solution to close down or open up the screen along the vertical dimension.

My feeling is this will work best in my situation because:

This will give me the biggest projected image for all ARs without resorting to an anamorphic lens (2 m2 for 2.4 material and 2.7 m2 for 1.78)
I will certainly not have a problem with too little brightness even at close to maximum zoom - in this dark room if anything I may have to consider a screen gain lower than 1.0
The 5 programmable settings of zoom, focus, and vertical/horizontal shift should allow me to easily switch between 5 main AR projection requirements


I know a majority of people seem to be fans of CIH setups but I think at least 3 factors specific to my case make and the X35 make a CIW setup more appropriate: the lens memory feature of the X35, the short throw, and my desire to have as big and immersive a picture as possible.

I'd appreciate comments to either reassure me it makes more sense for my situation or point out if there is something I am overlooking. For what its worth I don't give much credence to the view that a cinemascope picture should be "bigger" than 1.78 material. I only watch one film at a given sitting anyway, so the argument that there is an "oooh aaah" factor from seeing the masking panels on the sides pull outwards for 2.4 material doesn't sway me. I simply want to project cinema material in the aspect ratio it was filmed in and use all of my projector panels to their full capacity in a relatively short throw room.

Dave M

I know what you mean!

I also have a jvc rs46 and a curved Seymour 2.37.1 screen. I'm about 3.80m of the screen wich is 95" wide. For me personally I don't have that immersive feeling people are talking about. CIW in my opinion would be more suitable if you have a smaller screen to have that immersive feeling and CIH is ok if you have a bigger screen.

If I zoom a 16:9 image so the complete sceen is filled then I get an impression on how it would be with a 16:9 screen and for me(!) and......honestly I like it more.
So maybe I made the wrong screen choice frown.gif
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post #4 of 8 Old 04-20-2013, 04:00 AM - Thread Starter
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Thanks for the input.

Kelvin your posts on the X35 are one of the reasons I picked one up. Still, I don't quite get what you are saying about using zoom meaning not using the full resolution of the projector panels. Surely this is an optical and not a digital zoom? If optical, the full pixel count of the panels should simply be being magnified when one uses a wider angle zoom setting on the lens.

I do take your point about potential image softness. I have the feeling I will decide this prior to building my screen and installing in the new room by projecting film content and determining the maximum zoom at which I am comfortable with the image quality. I'll then set up for projecting that image width for all content and masking top and bottom as needed.

Best,

Dave M

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post #5 of 8 Old 04-21-2013, 04:48 AM
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Quote:
Originally Posted by dave in gva View Post

Thanks for the input.

Kelvin your posts on the X35 are one of the reasons I picked one up. Still, I don't quite get what you are saying about using zoom meaning not using the full resolution of the projector panels. Surely this is an optical and not a digital zoom? If optical, the full pixel count of the panels should simply be being magnified when one uses a wider angle zoom setting on the lens.

I do take your point about potential image softness. I have the feeling I will decide this prior to building my screen and installing in the new room by projecting film content and determining the maximum zoom at which I am comfortable with the image quality. I'll then set up for projecting that image width for all content and masking top and bottom as needed.

Best,

Dave M

What he meant it , when showing a 2.35:1/2.4:1 aspect ratio picture on a 16X9 screen, the two black bars are the loss resolution of the picture. To compensate it properly, without loss of resolution, is to use the anamorphic mode to fill the full screen height and an anamorphic len to unsqueeze the widths of the picture on an 2.35:1 screen of the same picture height. To zoom in a 2.35:1 picture on a 2.35:1 screen, without using the anamorphic mode, will only magnifies the image which already loss that 15% of the full resolution. Hope that explanation helps!

Alex:)
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post #6 of 8 Old 04-21-2013, 05:03 AM - Thread Starter
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Oh sure. Yeah I was aware that the projected image at anything over 1.78 will contain some black bars top and bottom. Those will be masked out by the masking, but the projected image width will be as wide as I can get it and still be happy with the image.

Best,

Dave M

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post #7 of 8 Old 04-21-2013, 05:44 AM
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Looks like Richmond5 explained what I meant. If you zoom for 2.40:1 you aren't using the whole panel (though you are using the whole width of the panel).

It's a good idea to test things out before it's all set in stone. You might be perfectly happy with the image at full zoom:You might get a projector with particularly good convergence and lens for example, so no reason not to try. It's just that the other X35 and X55s that I've seen don't seem to look as though they are quite in focus and it irritates me (I feel like grabbing the remote to check and it one case I did and no further adjustment could improve it).

I presume that you've seen an X35 demo'd first? I'd hate to think that people are buying them just because I'm pleased with mine. redface.gif

Zooming: Been there, done that, bought the lens...
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post #8 of 8 Old 04-21-2013, 05:51 AM - Thread Starter
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Thanks Kelvin, actually I have my X35 since December. Although at the moment it is in another room which is longer and narrower. For the width I am throwing there (about 215 cm from a 400 cm throw) I am very happy with the image. I'll do some testing to see what the optical performance is like at full zoom and backed off a little.

Dave M

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