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Discussion Starter · #1 ·
I am going to be doing a 2.35 screen which is 128" D. I went to projector central's site to get the 16X9 width from my height.


Now my question. My width will be 89" cause my height is a constant 50".


It figured my optimal throw with the JVC Pro 20u to be 162" which is a throw ratio of 1.8.


I figured it with a throw ratio of 2.0 to get a distance of 178" for when I put the lens in front of the image.


Do I use their recommended throw of the 1.8 to figure my distance or should I stick with the 2.0 ratio?


Also when you change the screen gain things really get weird. I had planned on using a screen with a gain of 1.16.


I guess I'm looking for direction here. Do I use any of their numbers or do I just get the width of the 16x9 image for my 1.35 screen and leave t he cite and use the formulas here.


There are lots of variables here and I don't want to mess it up.


Is 178" too far for this projector with a 128" screen with a gain of 1.16?
 

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Are you using an anamorphic lens, or do you plan on zooming to fill your image? This is going to make all the difference in the world. When using an anamorphic lens, all you need to worry about it the image width at 1.78:1 (or the native aspect ratio of your projector). You want to get the projector as close as possible to the screen, but far enough away to avoid hotspotting. Your best resource for hotspotting information would to be to contact the manufacturer of your screen. If they recommend 1.6x the image width minimum, then I would try and place the projector as close to that as possible, taking into consideration the throw distance your projector can handle.


If you plan on zooming to fill your image, you are opening up a whole new can of worms and you need to determine how much zoom will be required to fill your 2.35:1 aspect ratio.
 

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Quote:
Originally Posted by RooRwOrks /forum/post/17056090


You want to get the projector as close as possible to the screen, but far enough away to avoid hotspotting.

If using a lens, then this is not quite correct. You need to ensure that your TR is with in the limits imposed by the lens. A small apperature means a longer throw, hence the zoom is reduced and the projector must be moved back.
 

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Sorry, I was quick to post, but hoping to get a little more information before going into much detail. CAVX is 100% correct, if using an anamorphic lens, you will actually benefit from increasing your throw distance to help alleviate the pin cushion effect. I believe 1.8x the image width or further is ideal when using a lens.
 

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Discussion Starter · #5 ·

Quote:
Originally Posted by CAVX /forum/post/17056213


If using a lens, then this is not quite correct. You need to ensure that your TR is with in the limits imposed by the lens. A small apperature means a longer throw, hence the zoom is reduced and the projector must be moved back.
Quote:
Originally Posted by RooRwOrks /forum/post/17059498


Sorry, I was quick to post, but hoping to get a little more information before going into much detail. CAVX is 100% correct, if using an anamorphic lens, you will actually benefit from increasing your throw distance to help alleviate the pin cushion effect. I believe 1.8x the image width or further is ideal when using a lens.


Guys thanks alot for the info! Yes I will be using a lens. I am right now thinking but in the air with panamorph. They recommend a 1.6 to 2.0 TR and they wold like me be near that 2.0 or bigger.

O hay disregard the above number s in the above post. This is where I am at now. . .


IF I only concern my self with the 16x9 width this is where I am at:


the screen is a 130.4 D with a gain of 1.30 (lets say a stewart ultramatt) so the 16x9 width is 90.6. I shoot for a throw of 2.0 and it gives me a throw of about 15'. when I use a xsl sheet I found that does light output I put in my Lunems of about 550 for the projector I am currently looking at (a JVC pro 20u) cause I know it doesn't do the real world of 900 lumens I get a brightness of 22.3 foot-Lamberts.


I know this is ok but when I use his adjusted 2.35 one I put in the same numbers and my foot-lamberts is now 15.1 which he shows as too low?


Do I use both or just worry about the 16x9 numbers like you all said?

Do I look at a brighter projector, but most of these high contrast ones are lower Lumens?

Do I go smaller with my screen? Don't really want to.

Can't move the projector closer cause then it will screw up my TR for the lens!


I'm really confused. I am trying to nail down the screen and projector before I begin anything cause it's all based on this. I am stuck with a depth of a room of 17'. that's it. the width isn't a problem for pic it will be 12' wide or 14 feet. haven't decided. i want ot get this stuff smashed out before I decide. I know my projector choice might change with cedia coming up but hey maybe it won't.


All I know is I am looking at a lower Lumen output for the projector most likely and I have a lens in the mix.


Can you guys give me some incite?


Thanks so much!

jimi
 

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If you would like to maintain image size, projector model, and throw distance, have you considered increasing the gain of your screen? At 1.8-2.0x the image width or further for throw distance, you can get Ultramatte 150 from Stewart which is a 1.5 gain white screen and not have to worry about any hotspotting issues. 15.1 fL is fine for a dedicated environment. THX certified theaters require 12-16 fL coming off of the screen, so you are in great shape as long as you are getting 550 lumens out of your projector. The thing to keep in mind if you plan to go this route is to make sure you have properly treated your room and view it in as dark of an environment as possible. If you increase the gain to a 1.5 gain screen, you will get a slightly brighter image which will allow you to run your projector in a lower setting saving bulb life. The downside to increasing the gain is you decrease the half gain (the angle at which the screen 50% as bright). If you are not incredibly off axis, this should not be a problem. I have a Firehawk G3 screen which is rated at 30deg half gain, but I view it at extreme angles sometimes and this has never been a problem. If you are planning on going with Stewart, sometimes it is just easier to establish what projector you are going with, your throw distance, and image size and leave the rest up to them to recommend the right material for your application.
 

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Discussion Starter · #7 ·

Quote:
Originally Posted by RooRwOrks /forum/post/17062405


If you would like to maintain image size, projector model, and throw distance, have you considered increasing the gain of your screen? At 1.8-2.0x the image width or further for throw distance, you can get Ultramatte 150 from Stewart which is a 1.5 gain white screen and not have to worry about any hotspotting issues. 15.1 fL is fine for a dedicated environment. THX certified theaters require 12-16 fL coming off of the screen, so you are in great shape as long as you are getting 550 lumens out of your projector. The thing to keep in mind if you plan to go this route is to make sure you have properly treated your room and view it in as dark of an environment as possible. If you increase the gain to a 1.5 gain screen, you will get a slightly brighter image which will allow you to run your projector in a lower setting saving bulb life. The downside to increasing the gain is you decrease the half gain (the angle at which the screen 50% as bright). If you are not incredibly off axis, this should not be a problem. I have a Firehawk G3 screen which is rated at 30deg half gain, but I view it at extreme angles sometimes and this has never been a problem. If you are planning on going with Stewart, sometimes it is just easier to establish what projector you are going with, your throw distance, and image size and leave the rest up to them to recommend the right material for your application.

Hey,


It's funny you post this info. I actually spoke with Stewart yesterday. I told them all my variables and they said exactly what you said. There first recommendation is the untramatte 150. they said with my off axis viewing I am in good shape with this screen. I asked about hotspotting and they said deff no prop.


Ok so here is the followup questions.

1. So with doing the 2.35 screen I DO have to take in account the brightness I am getting with the 2.35 screen and not just look at the 16x9 numbers for brightness? I highlighted this cause this iswhat I'm really confused about some say to take it in account others don't? just a question. trying to learn.

2. Should I look at the firehawk like you? how come you didn't go with the ultramatte if you were able to get the gain you needed with no hotspotting and then also get the larger axis you needed? just wondering?

3. also what is this sparkles i read about around AVS? some people say certain screen create bad sparkles? just wondering again.

4. also the projector is rated at 900 lumens but I know you can't go by that. from the reviews of the jvc pro20u the real world readings are between 650-550. should i be looking at the light output in this way. . .am i on the right path for figuring all this out or am i upping gain to get more light for no reason cause i real world I will be getting more lumens out of this projector?


i a week or 2 when my schedule allows I am going to view this projector again, but also the planar 8150 and the lower end sims2 something like the 50 or 60. i forgot it's the only one they have that is sub 10 grand. i forgot.


thanks so much


jimi
 

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1. So with doing the 2.35 screen I DO have to take in account the brightness I am getting with the 2.35 screen and not just look at the 16x9 numbers for brightness?

You will be dispersing the light onto more square footage, so yes, your 2.35 image will be dimmer. You will also lose some light with the additional optics. Again, if this is a dedicated environment, you will be fine with Ultramatte 150 for image brightness in 2.35:1


2. Should I look at the firehawk like you? how come you didn't go with the ultramatte if you were able to get the gain you needed with no hotspotting and then also get the larger axis you needed? just wondering?

- I went with Firehawk because my screen is in my living room and I like watching sports, playing xbox and ps3 on it, watching TV, and occasionally watch a movie some some ambient light. I have white walls, white ceiling, tan carpets, etc, so cross reflection is also a problem for me. I have the panasonic AE3000 which is rated at 1600 lumens, and my screen is smaller. This allows me to go with a 1.25 gain screen, and still get an incredibly bright image. I run my projector in the lowest setting and I am estimating I get just under 500 lumens.


3. also what is this sparkles i read about around AVS? some people say certain screen create bad sparkles? just wondering again.

- Sparkles no longer an issue with Stewart screens. They fixed this with the third generation of material. This will not even affect you if you choose to go with an Ultramatte screen. These screen have more of a sheen to them, not the grainy optical coating of some of the other models. I would have gone with either StudioTek 130 (1.3 gain white) or Ultramatte 150 if I was in a dedicated environment with proper treatment.


4. also the projector is rated at 900 lumens but I know you can't go by that. from the reviews of the jvc pro20u the real world readings are between 650-550. should i be looking at the light output in this way. . .am i on the right path for figuring all this out or am i upping gain to get more light for no reason cause i real world I will be getting more lumens out of this projector?

The one thing to keep in mind is your bulb will get dimmer after use. The last thing you want to do is get a screen that is just above the minimum and have to run it on the brightest setting to get a viewable image. I run my projector in economy mode on the lowest setting. This gives me the flexibility of turning it up to watch with moderate levels of ambient light. Even if this is not the case for you, you can always throttle down your projector to save bulb life. A 1.5 gain screen is definitely not overkill for this setup.
 

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Discussion Starter · #9 ·
Thanks alot for all the info. So lesson learned is make sure I know going int otall this what the projector will put out in diff modes for thinking ahead.


I guess 1.5 just seems so high compared to what everyone else is using out there. I know I have to look at some of the 3.25 setups out there and see what else everyone is using and such.


Thanks so much for all the info. It will deff help put.


On a lighter note I sat with my buddy today to clean up my basement floorplans and get new numbers on them so I can post em up and get some solid ideas now.


I'm going to start a tread for my build in a few days when I get all my info together.


jimi
 

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Quote:
Originally Posted by jimim /forum/post/17067549



I guess 1.5 just seems so high compared to what everyone else is using out there. I know I have to look at some of the 3.25 setups out there and see what else everyone is using and such.

Well try not to think this way
Your setup is YOUR setup, not anyone else. If there was one end all screen, then it would be a lot easier to decide. Screen manufacturers have different versions of material to accommodate every installation just as speaker companies have different type of speakers for specific applications. What screen is going to work best for you may not be the same for someone getting a screen of the exact same size. There are just too many variables to consider to say "x" screen will work for any application.
 
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