1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

bounced ambient light advice

Discussion in 'Projectors, Screens & Video Processors' started by dan_wade, Feb 17, 2004.

  1. dan_wade

    dan_wade
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    I have just bought my first projector, a Panasonic ae500.
    850 lumes, so its pretty bright/high contrast for a LCD projector. I am after screen advice really. Im just using a plain wall for the time being, but one thing ive noticed is that there is alot of ambient bounced light in the room from the wall. This is lowering my contrast, and slightly washing out my blacks.

    Does anyone recomend any screens that can obsorb light? I was looking at the DRH projector screen sight. The better you go though, the more reflective they are, but wont this mean they will reflect more light in the room, which is a bad thing for a LCD projector?

    I even heard that going with a grey screen might be a good idea, to give better black levels. I recently used my projector at a friends house, who had dark red walls, i it seemed alot better contrast and colours than using it on my white walls where i live.

    Any ideas?
    Cheers,
    Dan.
     
  2. buns

    buns
    Banned

    Joined:
    Apr 29, 2001
    Messages:
    6,066
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    58
    Location:
    Belfast
    Ratings:
    +1
    i dont like the idea of high gain screens with these projectors, but i know some will argue their use 9though often they are daft americans using a screen 3 times the width they should!). I personally use a light grey screen with my (similar) Z2...... well worth a diy try....

    your white wals likely arent helping...... short of having silver or mirrors, it cant get any worse! :(

    ad
     
  3. KraGorn

    KraGorn
    Active Member

    Joined:
    Aug 30, 2003
    Messages:
    4,740
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    68
    Location:
    Warrington
    Ratings:
    +27
    I used a Draper grey screen with my Panny AE300, it had a 0.8 gain. It worked quite well though the 300 was a bit too dim for it in 'eco' mode, in 'normal' it was okay but that increased the noise beyond tolerable.

    I now have an Onyx fixed-screen with 1.2 and before selling the 300 I must say I did notice the blacks weren't as good as with the grey screen.

    I actually tend to prefer brighter images than others I think, you may very well find the decrease in brightness a price worth paying to get better blacks and less back-scatter.

    Since my screen is now in a non-dedicated room I hang black sheets from hooks in the ceiling across the ceiling and down the two side walls when viewing something 'seriously', works very well.
     
  4. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,789
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    What a screen with gain does:

    Tends to reflect light generally back in the direction it came from. The greater the gain, the greater this effect. Results

    a) ambient light tends to be reflected back towards the wall or ceiling (etc) rather than towards you so improved contrast

    b) projected light tends to reflect back towards the projector itself - so if you sit in roughly the same direction as the projector, all well and good. If you sit off centre (etc) you lose brightness of the projected image.

    What a grey screen does:

    Does not reflect all of the light coming from the projector. Absorbs some of it. Suppose it absorbs 10%. Your whole image is 90% of its maximum brightness.

    The stray light hitting the walls is also only 90%. Suppose the walls reflect 10% of the light hitting them back onto the screen (the rest goes somewhere else). That's 9% going back onto the screen. And 10% is absorbed again, so you see 8.1% of the reflected light.

    Compare with a white screen (suppose it reflects 100%). 100% goes onto the walls, 10% is sent back to the screen and 100% of that gets to your eyes. You see 10% of the reflected light.

    So, the grey screen gives you a 1.9% benefit (given these hypothetical figures).

    What dark decor does:

    (Assume a white screen which reflects 100%). 100% hits the walls; walls absorb (say) 90% but only relect 10% of what's left back onto the screen - the rest goes elsewhere. 1% of light returns to the screen, 1% is what you see.

    Conclusion: Dark paintwork.
     
  5. Rattus

    Rattus
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Hi Dan,

    There is a great deal of confusion generally about the physics of projection and I wouldn't profess to be completely clear on some of the more psycological effects, but let me give you a little lead in to screen issues.

    The washing out effect you see in your blacks is due to the diffuse reflection of ambient light. Ambient light hits the screen from most directions and is reflected off in most directions. We use diffuse reflective material whether it is white or grey (gray) so that the image is visible from anywhere in the viewing room, and shows no central hotspot.

    Higher gain materials have a more specular (mirror like) or retroreflective surface. These both cut down on the diffuse reflection of ambient light, since only light coming from the rough proximity of the projector is reflected towards the prime viewing area. The downside is that the image is bright in theis viewing area but fades as you move away from that area.

    In extreme examples, you can see the image actually being bright in the centre, fading off towards the edges, as if vignetted (photograpic technique/problem of darkening edges of a photo)

    So the advice as ever is work out where you intend people to sit to watch, how much ambient light you wish to watch in, then go and look at some screens, preferably in those conditions, with a similar projector.

    Obviously cutting down the ambient light level will improve the contrast in the blacks. I'm looking at moving to a darker colour scheme in the living room at home.

    Also, have a look for info on bias lights, I posted a link in a previous post.

    Good luck

    Martyn
     
  6. dan_wade

    dan_wade
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Well, im renting a flat, so i dont think i can change that much, plus i think painting the walls darker is a little OTT for me at this moment.

    I dont really mind having a slightly darker image, if it means im getting better blacks, and in my eyes, better overal contrast.

    Does anyone here have any of the DRH screens with their Z2/Panasonic ae500?

    Buns, where did u get your grey screen from?
    Have u got any screenshots of your setup?

    Cheers,
    Dan.
     
  7. gothmog

    gothmog
    Standard Member

    Joined:
    Dec 17, 2002
    Messages:
    204
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    16
    Location:
    Sunny Shipley
    Ratings:
    +0
    Might be worth having a look at a neutral density (grey :) ) filter before committing to a grey screen as the effect is pretty much the same (assuming a white wall/screen ;) ).

    You can use high (ie 2+) gain reflective screens to reduce the problem as these reflect more light back at the viewer rather than diffusing light like most standard screens do but then you run into problems like hot-spotting etc and it can get a bit nasty, and expensive.

    Paint the world black, it's the only way to be sure :)

    -- Jon
     
  8. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,789
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    A ND filter is NOT as beneficial as a grey screen. Using my example figures for a white screen above the maths becomes:

    Suppose the ND filter absorbs 10% of the light (the same as the hypothetical gray screen). The white screen reflects, say, 100%. But the PJ with filter is only doing 90%. So 90% goes onto the walls, 10% of that (ie 9%) is sent back to the screen and 100% of that gets to your eyes. You see 9% of the reflected light. Compare to 8.1% for a grey screen and no filter.
     
  9. dan_wade

    dan_wade
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    thanks Nigel.
    Does anyone is there are screen which are both grey and have a reflective capacity? This seems like the best solution as aposed to painting my walls. Im runing through component in progressive scan, so i know the connection is ok.

    Cheers,
    Dan.
     
  10. Kramer

    Kramer
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Merged with your (identical) thread in the screen forum.

    Please don't open identical threads/dulpicate posts.
     
  11. Rattus

    Rattus
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0


    Well, that does kind of describe the Stewart Firehawk, if you're happy forking out a months rent (depending upon screen type)

    http://www.stewartfilm.com/engineering_specifications/firehawk.html

    Have fun

    Martyn
     
  12. wither2000

    wither2000
    Active Member

    Joined:
    Oct 16, 2003
    Messages:
    148
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    21
    Location:
    Bristol
    Ratings:
    +4
    Dan,

    I have had a similar problem of Ae500 and light walls decreasing image contrast. Rather than painting the room black, I have pinned dark coloured but lightweight fabric to the ceiling so it hangs just in front of the walls and across the ceiling. This has improved contrast and blacks, and can be removed by taking out a dozen drawing pins.

    Ian
     
  13. dan_wade

    dan_wade
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Well, pinning dark sheets seems a good way of solving some problems without having to paint, but it think i might look a little untidy. I would rather spend the money on a decent screen that would solve alot of the problems. Im not unhappy with the results ive got at the mo, i would just like slightly darker blacks, without having to take the projectors brightness down.

    The firehawk look spretty cool. Ideal really. Does anyone own one of these? Coundn't find any place in the Uk that sells them, and they dont give any prices for the models?
     
  14. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,789
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    Suggestion: Dark coloured rollerblinds on the walls that are either side of, and perpendicular to, the screen. Roll them down when watching; roll them up when not watching. Hide them behind a ceiling feature (such as a fake cornice) when up.
     
  15. Yandros

    Yandros
    Well-known Member

    Joined:
    Oct 13, 2003
    Messages:
    2,711
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    133
    Ratings:
    +531
    Hmm, interesting one Nigel. That had occurred to me too for our lounge.

    Then all you need is to motorise your wall blinds along with curtains and screen, and you have the ultimate pose factor when the mates come round :D
     
  16. ailean

    ailean
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    Until the kids use them as black boards one day and forget to mention what they've drawn on them before you're mates come round and you press the button. ;)

    I would be tempted in a dedicated room but even with the gothic influences in my life blacking out a living room feels wrong. In a dedicated room I'd probably go with dark velvet drapes everywhere and overplay the darkness factor with a horror theme and some dry ice from behind the screen. :)
     
  17. inzaman

    inzaman
    Moderator

    Joined:
    Dec 16, 2002
    Messages:
    7,883
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Derby
    Ratings:
    +935
    Dan i had or have the same problem with my Z2 and cream ceiling and wall above the picture rails. I made my own screen and painted this a mixture of icestorm 5/6 which has solved a lot of the problem. With just a white screen the image seemed to be glowing and just looked washed out. I am probably going to get a da-lite hccv screen which is grey but has a positive gain so am hoping to get the best of both worlds? i.e improved contrast and improved picture brightness
     

Share This Page

Loading...