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Screenplay 7205 & Screen gain

Discussion in 'Projectors, Screens & Video Processors' started by Timbo21, Apr 21, 2005.

  1. Timbo21

    Timbo21
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    Hi everyone,

    I will be buying a screenplay 7205 & I've been advised to use a 0.8 gain grey
    screen, which surprised me a bit, since I though this was quite a specialist
    gain.

    Technical info is 1100 lumens pj brightness, 2200:1 contrast.

    Screen size would be 80" diagonal (69.7"w X 39.2"h)

    Viewing distance is 11 ft.

    Would be viewing most of the time at night & am planning to get blinds, which would get rid of most light during day. Also, area where screen will be is pretty
    dark area in the room anyway.

    Can anyone give me any info if this gain is okay with my setup. Additionally, I
    won't be running pj on full lamp mode.


    Thanks,

    Tim. :)
     
  2. nwhitta

    nwhitta
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    Grey screens are good if you have some ambient light in the room. However if you can control ambient light, either by watching at night or using effective black-out blinds, a white screen will probably give better colour reproduction.
     
  3. foghorn

    foghorn
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    A Grey screen with a 0.8 gain has probably been recommended to you because the 7205 are quite bright projectors. The Grey screen is designed to offer better contrast and colours.

    Find out who makes the screen and they should be able to send you a sample to try.

    Having looked at a 0.8 Grey screen sample, without doubt the screen produced deeper blacks and it also to my eye slightly subdue the image (less bright).

    Foghorn
     
  4. MikeK

    MikeK
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    Well, if you can accomodate a grey screen, I'd go that way myself.
    The problem for many is that they can't, so in many situations, grey would be the wrong choice!

    In your case however, you have a fairly powerful projector, and a modest screen size requirement in relation to that, so it shouldn't be a problem - in fact it'll probably be a bonus
    You may find you have to tame the light ouput of the projector - you can use ND filters, but they really don't have that much granularity - they typically cut light by 50%, 75% etc etc. You can get lower values but these tend to be specialist - not easily obtainable. Gary Lightfoot is probably the projector filtermeister on these forums!
    Or you can use a grey screen!

    Ambient light control means more than just shutting the curtains and drawing the blinds though :) When you are projecting, the light from the image bounces off the screen, round the room and reflects back onto the screen, lowering contrast - if you have light coloured walls and ceilings (ie most living rooms) then the effect is greater.
    The ideal room would probably be large with a high ceiling, all flat black matt, with black carpets, no windows, a light sealed black door, and yourself in a ninja suit sat on your flat black coloured chair! :) but there's hobbies and there's, well......hobbies :) :)

    A grey screen also helps to tone this effect down a bit!

    The other bonus is that grey screen give you better black levels - but you don't get anything for free - this comes at the price of slightly muted colurs in relation to white screens.
    I suspect you won't find this a problem with your projector power and modestly grey screen!

    Can you not get the dealer to demo the relative merits of white vs grey!
     
  5. Timbo21

    Timbo21
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    Thanks all for that.

    I guess I wouldn't be running the pj at full brightness, so I could get better
    lamp life. Will this make a difference? Mike K Would you still recommend grey?

    Also. the room will be decorated in a light peach coloured wallpaper.

    T.
     
  6. MikeK

    MikeK
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    Recommend may be a touch strong, as I prefer people to make their own mind up.

    Depending on personal preference, you are usually aiming for a screen brightness of between 12 and 22 FL (1FL = 1 lumen per sq ft). Your screen is around 20 sq ft, so you want somewhere between 240 and 440 lumens output from the projector if you use a 1.0 gain screen. I think the 7205 will be a tad brighter than this, even in ecomode - using a 0.8 grey screen will up the requirements to around 300-550, which should put you in the ballpark at the brighter end of the recommended screen brightness levels. This is OK, and will allow for a bit of dimming of the PJ over the life of the lamp. It should also improve the black levels slightly!

    BTW - you may or may not know that the actual lumen output from projectors, once setup for best video, often comes nowhere near the specs suggested level.
    ProjectorCentral measured the supposedly identical Toshiba MT800 at 560 lumens in ecomode, and while you can get variations between samples of the same models, they shouldn't be too dissimilar.

    http://www.projectorcentral.com/toshiba_mt800.htm


    Still, you have to bear in mind other factors as well.
    When you watch a normal TV with the lights on, it seems fine - but turn the lights off completely, and suddenly it seems much brighter - of course it isn't really, it's just the same, but we perceive it to be much brighter, for several reasons (the ambient light reflecting onto the screen, our pupils widening in the darker room etc etc).
    It's a similar thing with projectors too!

    Also, personal preference comes into play as well. Some people simply prefer a very bright TV like image, while others like to recreate the local Odeon as closely as possible and go for a much lower level - it's each to their own as they say!


    If the screen is expensive, and you want a feel for the relative merits of each (to avoid a costly mistake if the dealer won't exchange etc), then you can make a "demo" screen for around £20 - go to B&Q and get a piece of MDF cut to size a few inches bigger than your screen, say 72"" x 42", and paint one half white, the other light grey (Icestorm 5 or 6 is popular - if you get 5, you can lighten it yourself and experiment a bit).

    This should at least give you a feel for the issue!
     
  7. Timbo21

    Timbo21
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    Thanks again Mike,

    What I want is a picture which will give me vivid, bright, sharp colours without
    obviously looking overcooked. Are any of the gains most suited to this in my situation?

    I have ordered samples, but I haven't got the pj yet :(
     
  8. chrislewis

    chrislewis
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  9. Gary Lightfoot

    Gary Lightfoot
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    Bugger....

    Mike has said almost word for word what I would have said! :)

    As Mike said, a grey screen is best for improving black level and/or if you have ambient light or reflective walls in the room. If you have ambient light, then a grey screen with gain is better than a grey screen with a gain of less than one.

    Light coloured walls will reflect light back onto the screen to some degree or another, and this is where a grey screen can help as the grey helps keep the black level. A screen with gain can also reduce these reflections (the reflected light isn't aimed towards the seating postion as much, but more back to wghere it came from - the walls), and a grey screen with gain would be the best choice - provided you don't mind the grey screen when compared to the white. Can you get the pj first and project onto the wall? If you can, you will see if the other walls are creating a problem that you are aware of.

    I have a preference for "cinema levels" of light reflectance (prefer closer to 12ft lamberts and don't mind if it's less), so for me, I would probably go for a white screen with a gain of no more than 1.3, and use an ND2 filter to dim the output by half if it's too bright (which visualy isn't as bad as you'd think). If you don't mind how the image looks with the ND2 filter in place, then you won't mind how the image will look as the lamp reaches the end of it's life - they typically dim to half their initial brightness before you need to get a new one.

    Then, as the lamp ages and dims, you can remove the ND2 filter and get some brightness back. As Mike quite rightly says, you can typically reduce the advertised lumens by over 40% and that will be very close to how many lumens your pj will be giving you in video/film mode. The 7205 has accurate advertised contrast, but again, as Mike has pointed out, the lumens are less - it uses a white peaking feature for higher lumen output (useful for daytime viewing perhaps, at the expense of image quality). An ISF calibration revealed around 504 lumens so Mikes MT800 numbers were almost identicle.

    What made you decide on the 7205? Optoma's H78 is a nice machine too, but is quieter and has slightly better blacks and a little more contrast. It will be fine with your size screen, and an ND filter will be optional - I measured the H77 at 510 lumens so seems a similar brightness to the 7205. Being in London, you're not far from RTFM (Horsham) who not only has an H78 on demo, he also has a split grey/white screen in his demo room so you can directly compare a grey screen with a gain of 1.3 to a white screen with the same gain.

    He also has Sim2 products on demo if you needed some more comparisons.

    Gary.
     
  10. Timbo21

    Timbo21
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    Thanks Gary,

    I went for the 7205 since I can get a good deal on it.

    I've tried 5700, panny 700ae & sharp xv z200. The 7205 was the only one I was happy with. I suffered from rainbow on the 5700 & eye strain, but not so
    on 7205. I think the 7 segment colour wheel may help. I believe the H78
    has 6 segment colour?

    T.
     
  11. Gary Lightfoot

    Gary Lightfoot
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    Hi Tim,

    You've had a good set of demos so you know what you're getting, that's half the battle. The H77/H78 have an 8 segment colour wheel, the dark green segments help eliminate dark area dithering and artefacts. I find less lumens helps keep them less visible anyway, and for me that's a more than acceptable trade.

    Do you know what screen you saw the 7205 on? How did the image look to you on it and what were the viewing conditions like?

    Gary.
     
  12. Timbo21

    Timbo21
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    I just found out it was a 1.0 or 1.1 gain draper, about 5 ft wide in completely
    blacked-out conditions.

    I must say it looked v. good & the 5700 looked awesome there as well. I had
    demoed the 5700 at two other places and it didn't look that good. I didn't
    go for it since it does give me eye strain & can see rainbows on it.

    My preference is good TV-like colours rather than dingy cinema looks. I'm
    often not v. happy with pq when I go to cinema and is often too dark with
    not enough colour.

    So just to recap. I could get a 1.3 gain screen & use ND filter, which will reduce brightness by 50%, or 0.8 gain screen. But I suppose taking my demo
    conds. into consideration a 1.0 gain screen would be the one. :suicide:

    Now I'm confused. :confused:

    I've got samples coming from Carada, but I wonder how much I can tell from
    a screen piece the size of 1 m or so?

    Or...can I use ND filter with 1.0 gain, or will that be too dim?

    I like the idea of being able to get some brightness back after lamp has dimmed.

    Tim ( :confused: )
     
  13. Gary Lightfoot

    Gary Lightfoot
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    If you prefer video levels to cinema levels then that helps give a direction - a 1.2 or 1.3 gain will be fine as you're use a smaller screen, and the ND2 filter would be good for keeping the levels reasonable. If you decide on the ND2, you will initialy think it has made the image too dim - we're prone to preffering brighter images, so you have to give yourself time to become accustomed to the reduced brightness.

    The advantage of a screen with gain is that you can go dimmer with a filter. If you get a lower gain, you can't go brighter. Samples aren't always the easiest things to compare, but if you can blue-tac them to a wall and project an image, you'll see which samples will stand out.

    The screen with a gain of unity will of course be identical to the conditions you demo'd in, so I can see why you want to go that way. The filter will still help though, but not as much as it will reduce the brightness more so will have to be removed earlier.

    Will you be using a fixed screen or a pull down? You could make your own screen using wood and blackout cloth which is around unity gain, and then decide later if you're happy with it. The scloth is about £5 a meter (£10 to make yours) and the wood can be 2x1 from B&Q, you just stretch and staple the cloth to the wood. I made my own screen and pics are on my web-site below. You can buy proper screen material later and stretch/staple it over the frame if you want some gain later on (which is what I did).

    Gary.
     
  14. Timbo21

    Timbo21
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    Thanks Gary,

    It would be a fixed frame. However, I'm not much of a DIY enthusiast & haven't got things like saws & workmate so I think I'll skip that one.

    The higher gain with ND filter sounds like it might be the way to go.

    The 1.0 gain at the demo was good, but I don't think I would mind if it dimmed
    a little over time, but if it would dim by 50 % after lamp half life I think that would be too dim on a 1.0 gain.

    What do you think?
     
  15. Gary Lightfoot

    Gary Lightfoot
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    It's a small screen so will look pretty bright. Mikes ft lambert calculations are how we measure screen reflectance so you'll be getting around 25ft lamberts I think - twice what you'd expect at the cinema. :)

    At half life, it will be 12.5ft lamberts. Adding the ND2 will bring you down to 12.5 and I find less than 10 very watchable, but that's me. You prefer brighter so you might find adding the filter too dim for your liking. If the screen was a 1.3 gain, you'd get 32ft lamberts which is very bright. Add the ND2 and you end up with 16. When it dims, you could remove it to get back above 16. As Mike said, it's difficult to make some recommendations because it's a personal thing.

    Any screen at that size without a filter will be bright enough for you and should remain pretty bright for most of the lamp life. If it's too bright, you can add a filter later if needed, or just get one to try. You could probably sell it on in the classifieds if it's not what you need. Getting the pj first and projecting onto a wall with samples will be a start to finding out what you want from a screen.

    Gary.
     
  16. Timbo21

    Timbo21
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    Thanks Gary & Mike for all your help.

    :)

    T.
     
  17. Gary Lightfoot

    Gary Lightfoot
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    You're welcome.

    Let us know what you think of the pj when you get it home, and your findings of the screen samples.

    Gary.
     

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