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Discussion Starter · #1 ·
Hi everyone,


I need your help on understanding the projection distance and how that determines where you mount your projector.


Equipment List: (screen not purchased yet) - all other equipment has

Projector - PT-AE4000U

Screen - SMX 237.1 Curved (120 viewable width x 50.7 viewable height) = 130.2 diagonal - gain 1.16

Anamorphic lens - Optoma BX-AL133 with automatic sled - from what I understand, its basically a UH380. Is this correct?


Ok, the Panasonic manual states to use the following to figure the projection distance - diagonal screen size x 1.256 -0.04 = minimal projection distance and diagonal screen size x 1.899 - 0.05 = max projection distance.


Manual: http://www.panasonic.com/business/pr...4000/index.asp


So what I came up with is 130.2 diagonal screen x 1.256 -0.04 = 163.4912 inches or 13.6 ft minimal throwing distance and 130.2 diagonal screen x 1.899 - 0.05 = 247.1998 inches or 20.6 ft max throwing distance. Is this correct?



If the above calculations are correct, and utilizing the projector calculator pro and putting my projector back to the minimal distance of 13.6 ft would give me an image brightness of 15fl and fill the 130.2 inch diagonal 237.1 screen. Is this also correct and does the anamorphic lens change this formula?


Any assistance is greatly appreciated. Thanks, Dean
 

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I can't help you with the lens calculations, however I would ask where you are getting the figures to calculate the fL on screen? If you are assuming the AE4000 produces 1600 lumens, you could be in for a disapointment: That is only in 'Dynamic' mode, which is horribly inaccurate and clips certain colours that can't be calibrated out and uses a high colour temperature. The nearest to accurate out of the box mode is Colour 1 (or 2 depending on the individual lamp), but this relies on an internal filter that helps give a more accurate colour temp, but also reduces the brightness by above half.


I believe that Colour 1 mode will give you around 500 lumens, when the lamp is new, which of course will drop significantly in the first 100 hours or so, then fall slowly from that point until the lamp reaches half life (approx 2000 hours). You can use 'Normal' mode which doesn't use the internal filter, but is therefore much less accurate and some of the brightness is lost if you then calibrate in this mode (my AE3000 ended up hardly any brighter than Colour 1 for example, though the AE4000 has a lamp with more red, so this may help some).


Therefore I would strongly urge you to reconsider having either such a large screen with this projector or perhaps change for a screen with more gain (though I don't think this is an option with an AT screen).
 

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Discussion Starter · #3 ·
I thought I had read that the calculator was way off on the lumens, but here is the link that I used http://www.projectorcentral.com/Pana...ulator-pro.htm . You will have to adjust the calculator to 237:1 and 13.6 ft back with 1.16 gain to get my earlier calculations.


The AT screen is needed because I will be using in wall speakers for my F/L/C and I really want to go as large as I can with the screen.


What is the max diagonal screen that I should be looking at?
 

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If you look on the details of that page it says 1600 lumens. I'm pretty sure that I read they use the manufacturer's figures for the calculation. Therefore if you took the fL figure and divided it by 3 that should be a realistic ballpark for use in Colour 1 mode at approx 500-550 lumens.


If you want to use 'Normal' mode that may be around twice as bright as the Colour 1 mode, but as I said above it will not be very accurate (too green on the greyscale and the colour gamut will be oversaturated, not dissimilar to the JVCs that don't have CMS). In practice once calibrated Normal may well end up nearer 700-750 lumens.


I don't know what screen size would be ideal, but it's typical to aim for at least 12-14fL (plus more when new to allow for lamp diming). Therefore you need to have play with the calculator and see if you can get around 36fL: Then divide by 3 for the Colour 1 mode to give 12fL with an accurate picture or perhaps try getting around 18 fLon the calculator if you want to use 'Normal' mode uncalibrated or maybe 24fL if you plan to try calibrating normal mode. These will dial back to a real world 12fL reading approx.


Note that these are with a new lamp, so you may find you have to change the lamp well before the 2000 hours timer to keep somewhere near a decent brightness level.


Having said that I recently found that I'd been watching at around 5-6fL (I bought a lux meter, so I still have to perform a calculation based on estimated screen gain to get the actual fL). I upped my iris and lamp settings on my HD350 to give 12-14fL when I recalibrated and the image looks much better for it, though of course I could still see the image at 5-6fL, just that in comparison what I have now is an improvement: For example I can see shadow details which actually makes dark scenes look better despite the higher black level and daytime scenes don't seem like they were filmed at dusk.
 

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Quote:
Originally Posted by DeanHT /forum/post/19535255


hmm, if I use the calculator to get 36fl and then devide by 3 to get 12fl, the diagonal screen would be 64 inches. That is way too tiny!!!

Or divide your initial posted figure of 15fL by 3 to get 5fL on the screen size you stated or perhaps 8-9fL in Normal mode (after calibration), but remember this is with a new lamp: It may drop perhaps 20-30% in the first 100 hours so this would give you even less.


FWIW I had an AE3000 on my 112" wide 2.35:1 screen with 1.5 gain (equal to a 128" 16:9 diagonal as you're zooming, as I was then) and found it too dim. I then changed to the JVC HD350, which despite what the specs might imply, is actually much brighter than the AE3000 after calibration. I can hit a measured 95Lux at the screen which equates to approx 13.2fL* @1.5 screen gain and I'm at 600 hours and have some lee way to further open the iris as the lamp continues to dim. I didn't have the lux meter when I had the AE3000, but I did measure the fL with my i1LT when calibrating it and I think I measured about 4fL after 200 hours in Colour 1 mode.


(* Or 11.5fL if I take a more realistic figure of 1.3 for screen gain)


Welcome to the projector world of compromise.
 

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Panasonic know this too, which is why they put those misleading specs in their adverts (plus the other one about 100,000:1 contrast when in truth it's nearer 10,000:1 or even 5,000:1 if you're talking native contrast).



You could always add some extra masking to your proposed screen to reduce the size, thus making it brighter. Then when funds allow you could upgrade to something with a genuinly higher lumens output.


For now you could simply use the AE4000 in Normal mode, but just don't bother trying to calibrate it as this will further reduce brightness, just set the basic controls such as contrast and brightness: You may find you're perfectly happy with this result as plenty of owners seem to use this mode (it was too green on my AE3000, which also tends to make it seem brighter).
 

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Quote:
Originally Posted by DeanHT
Does the JVC models also over state their Lumens output? I was going to purchase the JVC-DLA-RS25 but read that it only had 900 Lumens.
From the reviews I've read and general impressions on here, they tend to quote the lumens at pretty much what you'll get when calibrated. That 900 lumens is still close to twice as much as a calibrated AE4000 don't forget. Plug the RS25 into the projection calculator and see what figures you get as they'll be based on the 900 lumens figure. The newer RS40 is slightly brighter as well and similar MSRP, though I believe the pre launch price from AVS is very tempting by all accounts.


It's still quite a big screen for the low gain that you're trying to light up however, so it's never going to be overly bright unless you went for some higher end model, but then you're talking much more money. Probably cheaper to aim for maybe 10-12 fL and change the lamp at 500 hours or so.


EDIT: I just put in the HD950 (the europe equivalent of the RS25) at 16' throw and 120" wide and get 15fL with a 1.1 gain screen. That might be a better starting point, though of course it will still dim a fair bit in the first 100 hours so maybe you'll be down to nearer 11-12fL by then. After this it would be a more gradual drop to half brightness at approx 2000 hours, so you'll end up at 7.5fL by then. Up to you when you deceide to change the lamp (I'd recommend getting Tecpel 531 light meter for aorund $80 to monitor brightness using a white test pattern).

http://www.projectorcentral.com/JVC-...ulator-pro.htm
 

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JVCs numbers are more accurate so easier to guestimate the fL for your given screen size.


Even if you end up with around 550 lumens on a new lamp (down to around 400+ after 100+ hours perhaps), you will still be getting something like 12+ fL on a 120" wide 2.35 screen which is fine in a light controlled room (you may be closer to 15fL with a gain of 1.16 when new). Even with lamp ageing, 7fL is bright enough and closer to what you get in a commercial theatre, so you should be fine if you like cinema levels of reflectance (rather than plasma like levels) which is what probably what you will end up with after around 400+ hours. Depending on how many movies you watch each week, 400 hours could be as long as 2 years (watching 4 hours a week every week).


Going above 12fL can have some negative effects by highlighting any source artefacts (especially if you watch any DVD or broadcast material), but it can depend on how well you notice things like that. Some people don't notice image noise at 20fL levels watching dvd as their preference is brightness above all else, so each to their own.


If you have a white wall, project onto that and see what size and brightness works for you. For an image to look half as bright, it has to have a drop in lumens of around 80%, so it will be some time before it becomes too dim to watch, although as Kelvin says, you may prefer it a little brighter if you get the chance to compare - we're naturally drawn to brighter images, but once the eye has adapted its the other image attributes that matter.


Gary
 

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Quote:
Originally Posted by Kelvin1965S /forum/post/19551858


From the reviews I've read and general impressions on here, they tend to quote the lumens at pretty much what you'll get when calibrated. That 900 lumens is still close to twice as much as a calibrated AE4000 don't forget. Plug the RS25 into the projection calculator and see what figures you get as they'll be based on the 900 lumens figure. The newer RS40 is slightly brighter as well and similar MSRP, though I believe the pre launch price from AVS is very tempting by all accounts.


It's still quite a big screen for the low gain that you're trying to light up however, so it's never going to be overly bright unless you went for some higher end model, but then you're talking much more money. Probably cheaper to aim for maybe 10-12 fL and change the lamp at 500 hours or so.


EDIT: I just put in the HD950 (the europe equivalent of the RS25) at 16' throw and 120" wide and get 15fL with a 1.1 gain screen. That might be a better starting point, though of course it will still dim a fair bit in the first 100 hours so maybe you'll be down to nearer 11-12fL by then. After this it would be a more gradual drop to half brightness at approx 2000 hours, so you'll end up at 7.5fL by then. Up to you when you deceide to change the lamp (I'd recommend getting Tecpel 531 light meter for aorund $80 to monitor brightness using a white test pattern).

http://www.projectorcentral.com/JVC-...ulator-pro.htm


Kelvin,


The HD950 and 120" wide screen is a new setup for you, yes?



What is your eyeball to screen distance with that setup?



What kind of screen?



...Glenn
 

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Quote:
Originally Posted by Glenn Baumann /forum/post/19552910


Kelvin,


The HD950 and 120" wide screen is a new setup for you, yes?



What is your eyeball to screen distance with that setup?



What kind of screen?



...Glenn

I think you misunderstood me. I put that spec in the projection calculator as it was similar to the RS25 that you mentioned. I don't own an HD950 myself and my screen is still 112" wide. The calculator gave 15fL which would allow you to close the iris a little on the HD950 when new, so that once the lamp dims a little you still have some headroom to open it up to retain around 12fL or so. As Gary says DVDs might look better at a slightly lower fL, hence why I have a setting that equals around 9fL for such discs.


I did see a HD990 this afternoon at the X7 launch. They were both on an SMX screen (maybe 1.1 gain like you're planing) but they only used about 8 foot width of it. I didn't take my meter to measure though
so I don't know how bright it was, only that they used normal lamp and about half aperture. Only the 3D stuff seemed a bit dimmer than I would have prefered, but that is like watching through an ND4 filter from what I saw today.
 

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Quote:
Originally Posted by Kelvin1965S /forum/post/19553502


I think you misunderstood me. I put that spec in the projection calculator as it was similar to the RS25 that you mentioned. I don't own an HD950 myself and my screen is still 112" wide. The calculator gave 15fL which would allow you to close the iris a little on the HD950 when new, so that once the lamp dims a little you still have some headroom to open it up to retain around 12fL or so. As Gary says DVDs might look better at a slightly lower fL, hence why I have a setting that equals around 9fL for such discs.


I did see a HD990 this afternoon at the X7 launch. They were both on an SMX screen (maybe 1.1 gain like you're planing) but they only used about 8 foot width of it. I didn't take my meter to measure though
so I don't know how bright it was, only that they used normal lamp and about half aperture. Only the 3D stuff seemed a bit dimmer than I would have prefered, but that is like watching through an ND4 filter from what I saw today.


Yes, sorry Kelvin, I did misunderstand!



Before I pull the trigger on a new screen I am still looking for real world application feedback on my JVC RS20 paired with a proposed 1.16 gain 120" wide Seymour or SMX 2.35 screen throwing from 16 feet and viewing from 11.5 to 12 feet. I am concerned with overall and long term brightness and possible screen weave visibility!


I guess I saw what I wanted to see in your HD950 comparison... a JVC with a 120" screen at a 16 ft throw!



...Glenn
 
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