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Discussion Starter · #1 ·
Hi All,


I just left a home theater design firm to see some DLP projectors. The design consultant told me that I probably wouldn't be happy with the performance of a DLP projector with a screen diagonal in excess of 100", even in a light controlled room.


It this correct? I was hoping on getting an Infocus ScreenPlay 7200 with a 120 to 135" screen. It this unwise? My room is 15' x 24' x 10'.


Thanks in advance.


Larry
 

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Larry, I have personally seen DLP projectors on screens up to around 110" and they put out amazing pictures. Screen type plays into it probably. I have only seen Firehawk screens for the most part. 120 - 135" might be getting up a little high but you can definitely see good results in the 100 - 120" range in my opinion.
 

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Larry


Two issues for me. Brightness and resolution.

Assumption is that htese are 16x9 screens.


The InFocus is very bright. So....


We ran a thread recently about calculating optimal screen sizes and viewing distances for different PJ's. It was all about acceptable resolution and when pixel structure would become apparent.


My version was based on pixels per square inch (ppsi).


The conclusion was that screen door would become an issue when ppsi dropped below 220. This was at an optimal viewing distance of 11 feet.


So...


InFocus 7200 has 921600 pixels


Your 120 inch screen would have 6139 square inches

At 11 feet your ppsi would be 150 - it's too low

You'd need to move back to 17 feet to reach 220 ppsi


Your 130 inch screen will have 7204 square inches

at 11 feet your ppsi will be 128 - even lower

You'd need to move back to 19 feet to reach 220 ppsi


Hope this is understandable and useful.

Check out the thread as some very interesting ideas were in there.


Rob
 

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My demo room has a 150" diag. screen on the infocus 7200. Not one person has complained about it (seating distance 16' and 20').
 

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No complaints with a 133" diag. in room with controlled lighting.
 

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Discussion Starter · #6 ·
Quote:
Originally posted by Kei Clark
No complaints with a 133" diag. in room with controlled lighting.
Hi Kei,


Thanks for the response. What is the distance to your seating and what type of screen are you using?


Thanks.


Larry
 

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Using Da-lite High Contrast Cinema Vision, the seats are not permanent (which is a good thing since we suffered a flood recently) but I'd say about 15-16' distance from screen.


Just a note, I think 119" would have a good choice in this room but I was talked into the larger screen because a friend of mine is into "bigger" picture.
 

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Discussion Starter · #8 ·
Quote:
Originally posted by Robert Holloway
Larry


Two issues for me. Brightness and resolution.

Assumption is that htese are 16x9 screens.


The InFocus is very bright. So....


We ran a thread recently about calculating optimal screen sizes and viewing distances for different PJ's. It was all about acceptable resolution and when pixel structure would become apparent.


My version was based on pixels per square inch (ppsi).


The conclusion was that screen door would become an issue when ppsi dropped below 220. This was at an optimal viewing distance of 11 feet.


So...


InFocus 7200 has 921600 pixels


Your 120 inch screen would have 6139 square inches

At 11 feet your ppsi would be 150 - it's too low

You'd need to move back to 17 feet to reach 220 ppsi


Your 130 inch screen will have 7204 square inches

at 11 feet your ppsi will be 128 - even lower

You'd need to move back to 19 feet to reach 220 ppsi


Hope this is understandable and useful.

Check out the thread as some very interesting ideas were in there.


Rob
Hi Rob,


Thanks very much for the explanation and the reference to the link Calculating viewing distance and screen size . It is very helpful.


Perhaps this is a little off the topic that I started, but could you comment on the "optimum" projector distance for the InFocus 7200? As I mentioned my room is 24 feet long, and I wanted to mount the projector at least 16 feet and from the screen to permit throwing a sufficiently large image and to minimize the lengths of video cable (my rack will be in the rear of the room).


For example, if I choose a 110" screen the InFocus Projector Calculator says that the projector should be mounted between 11.909' and 16.618'. What are the trade-offs between the lower distance and the higher distance? It would seem that the lower distance would yield a brighter image, but that would put the projector in the middle of the room and video interconnects would be prohibitively long. Conversely at the higher distance I would be saving 5 foot of video interconnects, but would 5 feet noticeably effect the picture quality in terms of brightness?


Thanks.


Larry
 

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Larry,


You generally don't want the lens at either extreme of the zoom. The optics are better towards the middle of the range.


In a light controlled room the brightness of either distance is equal. Brightness suffers when the screen gets bigger, but not when the distance to screen is farther.
 

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I respectfully disagree.

You generally want the 7200 at the far end of the range to prevent "hot-spotting" which can occur with bright PJ's at close distances.

Optic differences aren't significant.

Just MHO, HTH.
 

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Larry


My issues with screen size are brightness and screen door. they are very different issues.


To be more accurate I see screen door as the point at which you start to see that it's video rather then film.


On brightness there are simple calcs around foot lamberts and lumens across the screen space. I started the other thread because I had not seen much about the film / video issue.


The posters on the other thread concluded that there are three variables.


The projector - driving resolution

The size of the screen

The distance from the screen


From this, if you see the other thread and my earlier post you can easily work out the optimum distance for each projector at each screen size at each distance.


======


The quoted distance from the screen from the manufacturer is a different discussion. This is driven by the zoom lens. They are stating that with their PJ with that screen size you need to place the PJ within a certain distance range. I don't buy the brightness argument when the difference is 5 feet.


Of course if you buy a long lens, that's adifferent story. there are many forum members who do this so I would imagine on a super bright InFocus you'd be OK.


The other thing to consider is whether you ceiling or floor mount.


Hope these ramblings are useful.


Rob



Quote:
Originally posted by LarryChanin
Hi Rob,


Thanks very much for the explanation and the reference to the link Calculating viewing distance and screen size . It is very helpful.


Perhaps this is a little off the topic that I started, but could you comment on the "optimum" projector distance for the InFocus 7200? As I mentioned my room is 24 feet long, and I wanted to mount the projector at least 16 feet and from the screen to permit throwing a sufficiently large image and to minimize the lengths of video cable (my rack will be in the rear of the room).


For example, if I choose a 110" screen the InFocus Projector Calculator says that the projector should be mounted between 11.909' and 16.618'. What are the trade-offs between the lower distance and the higher distance? It would seem that the lower distance would yield a brighter image, but that would put the projector in the middle of the room and video interconnects would be prohibitively long. Conversely at the higher distance I would be saving 5 foot of video interconnects, but would 5 feet noticeably effect the picture quality in terms of brightness?


Thanks.


Larry
 

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We have 110 Firehawk. Our sales guy didn't think we should, he thought it would be way too big. He was trying to sell us on an HD1 DLP Yamaha.


We were already convinced we would be buying an infocus 7200. And when they came to see the set-up he indicated we Could have gone bigger with a projector like that...as he was helping me calibrate with Avia.


I guess He was to say the least very impressed with the IF7200...so much so they now carry the line.


I also agree we could have gone bigger but at 110 absolutely no complaints...Friend saw our set-up and bought the exact same thing.


Good luck with your decision...just remember GO Big or Go HOME.


Cheers,


Requis
 

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"You generally don't want the lens at either extreme of the zoom. The optics are better towards the middle of the range."


Any evidence to support this? I'd expect the best picture with minimum zoom (longest throw) for these reasons:


- The minimum beamprint on the lenses; aberrations, such as poor focus at the edges and color separation,tend to increase with distance from the lens center


- Higher contrast due to smaller beam divergence


- Less hotspotting, as cajunlab mentioned
 

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I definately agree with those virtues of a longer throw.


I don't have any evidence to back up my claim. Evan Powell from projectorcentral stated it once in a review and I just assumed it was true. Either way the difference in hotspotting from zooming *very slightly* would probably be close to nothing. Here is an excerpt from the review.

Quote:
Ideal placement for this screen size would be at a throw distance from lens to screen of about 14 feet—as far back as possible without hitting the extreme end of the zoom range. Why? When you have the lattitude to do so, it is advantageous to keep the angle of the thrown image as narrow as possible so that it bounces off the screen in a more uniform manner. Very short throw distances will cause light hitting the outside portions of the screen to bounce off at more oblique angles than the light with strikes the center of the screen. However, we also like to avoid the extreme ends of zoom lens, especially those with longer zoom ranges, since they tend to be optically more precise toward the middle.
 

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Larry,


Bob Williams, one of the designers of the SP7200, recommended that the SP7200 be mounted in the longest throw position possible to minimize hot spotting and because the lense has the greatest depth of field at that setting.


Although I have read several posts on the forum that the middle portion of a lense should yield the best picture, it does not on my SP7200. My SP7200 has better focus uniformity in wide angle and in telephoto than when set in the middle of its throw. However, you can only tell the difference when you stand with your nose at the screen and look at the sharpness of the individual pixels. In terms of actual video, you can't see any difference at all from a normal viewing distance.


In terms of hotspotting, having the PJ further from the screen certainly yeilds a theorectical advantage. I am not sure how visible the difference is in real life, though.


If you have to mount your PJ close to the screen, I wouldn't loose any sleep over it. However, if you have the room, then set the lense in its longest throw position and mount it as far back as you can.


Check out www.bluejeanscables.com when you are considering where to buy cables. The cost for longer cables vs shorter ones is minimal from them. And the quality of this type of cable can't be beat.


Because of its brightness, IMO, the SP7200 looks better on larger screens than it does on smaller. I have a 123 D. firehawk. I have seen my PJ on a friends 133" firehawk. Not a single person who has seen it has thought it was too dim. Quite the contrary, and I was running it in low power (low brightness) mode. Your consultant is just not familiar with this particular PJ.


In terms of how far back to sit - this is a matter of personal preference. And it varies with different PJs. Only by trying different distances will you learn what you like best. Most people seem to settle on a distance that is 1.5 - 2 times the horizontal width of their screen. I prefer 1.5 times my screen width, which is 14' back from a screen that is 9' wide and 5' tall.


Also, the Firehawk screen is a great match for the SP7200.


Glenn
 

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My Infocus 7200 is matched with a 110" Firehawk. I run it in dim mode. No complaints from anyone. I like to sit at about 16 feet which is 2 times the diagonal width of the screen at 1.5 times I see pixels.
 
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