Light Room - Low CR

Discussion in 'Projectors, Screens & Video Processors' started by crackazz, Nov 2, 2005.

  1. crackazz

    crackazz
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    If you have a room that is cream coloured with white ceilings and cream carpet, althouhg the room is well light controlled. Would you see any benefit of the high CR offered by the latest D5 / DLP projectors?

    Or would it be too close to call due to the effect of light bouncing around the room.
     
  2. cyberheater

    cyberheater
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  3. crackazz

    crackazz
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    So basically, a Z4 wouldn't look any better on CR with a HC3000 if the room had white walls rather then black ones.

    ???? :suicide: :suicide:
     
  4. cyberheater

    cyberheater
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    Your room enviroment sounds pretty grim from a contrast ratio point of view (sounds nice from a family point of view though :))

    If you project against your wall and you have any light from another source either in that room or entering it then it's gonna kill the CR. It'll convert that 5000:1 contrast monster into a 1000:1 constrast ratio or more likely worse.

    It should still look pretty good but not at it's best. But on the other hand. We can't all sit in a black velvet lined bat cave whilst dressed as a ninja can we.
     
  5. Peter Parker

    Peter Parker
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    Or can we? :D

    http://cgi.ebay.co.uk/ws/eBayISAPI....Z2QQsspagenameZADMEQ3aBQ3aTB2Q3aUKQ3a4QQfviZ1

    Light coloured walls etc don't necessarily effect the on/off contrast of your pj like ambient light will, as a dark scene will have less light reflecting off of the screen than a bright scene will. It's when you have a scene that contains both dark and light elements in the same frame that the bright parts will reflect light from the screen, onto the walls etc and then back onto the screen, washing out the dark parts. This type of contrast is measured as simultaneous white and black (ANSI contrast) and the most you can get depends on the pj (it's lens) as well as the room. DLP will have better ANSI capability than any other projector technology (LCD, CRT, LCOS etc), and can easily be 500+. With the room added to the equation 200:1 is not unusual. A mostly light coloured room or a rom with walls close to the screen could be as low as 100:1 though.

    You will easily notice it if you have a movie that has black bars either top and bottom or on the sides. As bright elements come into view in a scene, you may notice the black bars become lighter, and in certain cases, change colour to some degree. It can be quite distracting if you start to notice it, so in those cases black velvet/felt masking is very useful and can help reduce the apparent effect of it happening within the scene iteself.

    Gary.
     
  6. Lucas

    Lucas
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    I also have a cream coloured room and I can confirm the above. In really dark sceens, the PJ's capability for deep black and dark greyscale is not affected significantly.

    But in scenes with both bright and dark areas, the room light's up and so does the screen giving black or dark greys that are not as dark as they should be if the whole room, walls, ceiling etc was a very dark or black colour.

    In that sense my Epson TW10H with its misely 800:1 CR doesn't perform that much worse than a higher CR PJ (like DLP 2000:1) and I tested that.

    The higher CR or more precisely deeper black that I now want to have for my next PJ will really be useful if I dedicate a dark painted room for movies.
     
  7. crackazz

    crackazz
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    what if I said I project onto a proper screen which is actually ceiling hung about a foot from the wall and picture is dropped about 22" from that white ceiling.

    I understand the other problems now, just wondering if I could save a few pennies buying a Z4 as it wouldn't preform any better than a HC3000. But I guess that is only one parameter to consider.

    Thanks


     
  8. Peter Parker

    Peter Parker
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    Hi Lucas,

    If the pj is bright enough, a lens filter can help to dim it down enough to give you better blacks (at the expense of dimmer whites). An ND2 will halve the light output for example. A colour correction filter and recalibration will have the effect of dimming the blacks more than the whites, so you end up with more contrast as well.

    cracazz,

    You will see the higher CR in dark scenes and it may also give you a better black level depending on the white level - for a given amount of light output, the more cr you have, the blacker the blacks will be. It's only in brighter scenes that the intra-scene contrast is effected and can be dropped from say 400:1 to 100:1 due to light coloured walls etc, so in those scenes all projectors will look similar in that respect. Grey screens help reject ambient light so that can be an option to consider, though I would suggest a grey screen with a gain above unity. Less than ubity gain will make the image look duller compared to a white screen.

    Gary.
     
  9. crackazz

    crackazz
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    Thanks Gary, all very helpful...

    still not sure if its made my mind up yet tho :confused: LOL!



     
  10. Knyght_byte

    Knyght_byte
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    i have apple white walls and a pure white ceiling......my 7205 looks lovely :)

    ok im sure in a black room or at least dark walled room it would be even better, but quite frankly its more than good enough for me :)
     
  11. Peter Parker

    Peter Parker
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    The difference is quite noticable when going from a pj in a light room to a pj in a dark room or vice versa. I've seen it myself and the difference in black level performance is noticable.

    If you havn't seen a pj in a dark room to compare, then that's a good thing. :)

    Gary
     
  12. crackazz

    crackazz
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    So what would I see then in comparison, more detail in the darker areas / scenes, or deeper blacks or both?!

    Do lots of people buy blind?! it seems to be quite hard to find anywhere that actually demos PJ. I really need to see a HC3000 before I pull the trigger on buying one, but hate to do it with out seeing it first.

    What do people mean by a 'Hot' picture when refering to DLPs?


     
  13. Peter Parker

    Peter Parker
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    Hi Crack'

    If you did the comparison you would see both, but the most noticable would be the blacker bars. In my dark room my black bars looked blacker than some CRTs I've seen in rooms with light walls. I've also noticed how the black bars light up in bright scenes and sometimes get effected by the colour that's in the scene being displayed. It's not necessarily a deal breaker, just something that you may or may not notice, and to put it all into perspective, I would say that the majority of people with projectors have light rooms and like Knyght Byte are more than happy with the image they are getting.

    'Hot' could be referring to the whites being very bright. This is normally due to the image being uncalibrated so the contrast level is set incorrectly. You need to set the white (contrast) and black (brightness) levels using a test disk like DVE or Avia (which is for NTSC). You can use the THX Optimode but it designed for the DVD it's on rather than a blanket calibration disk, but it will get you in the ball park so to speak. See the 'sticky' at the top of the page for more info on basic calibration.

    Where are you? Someone may know a dealer or someone who can give you a demo near you.

    Gary.
     
  14. crackazz

    crackazz
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    Hi Gary

    Well, I've just sold my AE300 and was initially looking at a Z4 but the HC3000 has caught my eye. I believe it would be more of an upgrade than the Z4 but not just because its a DLP but for overall picture quality.

    Do DLPs suffer from a dithering effect? thought I read that somewhere?!

    I do have a copy of Avia and used it to good effect with my AE300, picture was very good on the PJ, just why did I sell it again??!?

    I live in St Neots, Cambridgeshire and have been in touch with Ivojo re both PJs. I think if I just got the Z4 and used ROnes settings I'd be more than happy with it, but... always the niggles in the back of mind that a DLP would of been the better choice. Although saying that the Z4 has the cool lens shift which would aid the setting up no end :) and would be £600 cheaper! thats a lot of films!

    Thanks JC


     
  15. Peter Parker

    Peter Parker
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    DLPs have to dither to get shades of colours - each mirror is either on or off, so to get a shade of a colour it will have to be off for a percentage of the time - full red would have the mirror on nearly all the time, and half red would have it flicking on and off approx 50% of the time, this is temporal dithering . Spatial dithering uses adjacent pixels to give the impresion of certain shades or image qualities IIRC. If the dithering is done well you don't see it happenning.

    Having a DLP which is very bright can make the dithering more noticable though, so I tend to aim for an image that reflects 12ft lamberts or less. You can probably work this out if you know the true lumen output of a given projector and calculate the reflected light relative to the screen size - divide th elumens by the square foot area of the screen and multiply the number by any gain. I use lens filters to give me the reflectance I want as well as for gaining more contrast from recalibration. I rarely see any dithering so for me it works.

    Not everyone notices the instances of dithering and if they do they don't necessarily find it distracting.

    Gary.
     
  16. crackazz

    crackazz
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    My screen is 3m from seating area and is 80" dia. This will be a bit on the bright side then I take it! Although lowering the lamp mode should help alot.

    huh, just read this on projector central re: a review of your pj garry

    "Contrast.

    The contrast rating of 3500:1 is a theoretical spec. Since consumers have been conditioned to be sensitive to contrast specs, manufacturers tend to quote theoretical maximum contrast ratios that could never be achieved in a typical home theater environment. It is important to recognize that subtle changes in black levels on the screen have enormous impacts on the perceived contrast of the image. In a typical home theater or multimedia room, light from the projected image on the screen will be reflected off walls, ceiling, carpet, furnishings, etc., and back onto the screen. This reflected light has no impact on highlights, but it illuminates blacks and thus compresses the overall contrast range of the image on the screen. Ambient or reflected room light is therefore a great equalizer of theoretical contrast ratings among competing products.

    Therefore we would caution buyers against the prevailing tendency to place undue weight on the differences between contrast specs on high contrast DLP projectors. Unless you have a very dark home theater room in which walls and furnishings absorb reflected light, the actual difference in real life contrast between projectors will not be as dramatic as the sometimes radically different contrast specs would lead you to believe."
     
  17. Peter Parker

    Peter Parker
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    I measured my H78 (non DC3) at 550 lumens in high lamp and 425 in low lamp IIRC, so considerably less than advertised.

    The figures aren't necessarily theoretical - they can be achieved, but at the expense of video quality. If you ramp up the RGB contrasts individualy, you'll get a much brighter image that is very blue/green in apearance. If you don't set the contrast and allow it to clip, you increase the output further. Reduce the black control (brightness) and you end up with no shadow detail either. With DLP there is a 'white peaking' feature that enables the DMD to continue switching during spoke time and that increases the output further. This way you end up with a very bright but very innacurate image that lacks detail and is unwatchable. That's when they measure the lumens and contrast capability. If you use a colour correcting filter you can make use of some of that extra contrast and light output (with recalibration).

    They quite rightly mention the effect of the room and ambient on the image and on/off and ANSI contrast.

    Gary.
     

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