1. Join Now

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

Projector Measurements

Discussion in 'Projectors, Screens & Video Processors' started by Rob Sinden, Jul 30, 2005.

  1. Rob Sinden

    Rob Sinden
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 30, 2005
    Messages:
    2,588
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Newbury
    Ratings:
    +2,037
    Why doesn't Sim publish brightness readings for their projectors?

    Surely you need a certain level of brightness to recreate the pictures you'll see at a cinema?

    Is there a certain level you should look out for?
     
  2. RTFM

    RTFM
    Active Member

    Joined:
    Mar 6, 2003
    Messages:
    1,014
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    38
    Location:
    Horsham, West Sussex
    Ratings:
    +17
    Sim2 single chip DLPs are approx 800 ansi which is a good level of luminance for home use in controlled lighting conditions.

    Good contrast and black level are more important than published brightness figures.

    A white screen with a small amount of gain, say 1.3 is an ideal match for these DLP projectors.

    Jeff
     
  3. Rob Sinden

    Rob Sinden
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 30, 2005
    Messages:
    2,588
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Newbury
    Ratings:
    +2,037
    Hi Jeff

    Thanks for that. Is that something in the manual or have you measured it.

    How does that equate to 12fL that is the minimum target for commercial cinema?

    Sam
     
  4. RTFM

    RTFM
    Active Member

    Joined:
    Mar 6, 2003
    Messages:
    1,014
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    38
    Location:
    Horsham, West Sussex
    Ratings:
    +17
    Sam, Sim2 do not publish brightness figures. I have not measured the output as it is largely academic in as much as the peceived brightness will be affected by the size of screen, screen gain, viewing position, projector position etc.

    Jeff
     
  5. Liam @ Prog AV

    Liam @ Prog AV
    Well-known Member AVForums Sponsor

    Joined:
    Oct 18, 2002
    Messages:
    8,498
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Kent
    Ratings:
    +827
    You will have no problem calibrating a Sim2 down to 12fL. You could probably run it at 20fL if you wanted but you would no doubt crush a lot of detail in the process!! 12fl alone is purely a measure of brightness, not a measure of whether the image is still accurate at said brightness levels. In terms of ANSI figures, a calibrated projector will often be around the 400-500 ANSI mark.

    The Sims aren't the brightest around and will appear dimmer than other projectors when ambient light is introduced into the room. But there shouldn't be ambient light in the room anyway!! In blackout (or near blackout) conditions, whatever the figures say a Sim2 image offers hugely impressive black levels and contrast where the brighter projectors are perhaps *too* bright to do so as well, losing that ultimate contrast edge.

    They are often partnered with a 1.3 gain screen just to bring up that bit of punchiness. This is as most reference setups would be calibrated (the industry reference standard is a 1.3 gain projection surface, and as many footlamberts as you can get before you sacrifice other areas of the image). The leading reference material is Stewarts StudioTek 130 (and now there is a reference grey material - Greyhawk RS). But you will find Da-Lite 1.3 gain screens are very close, and again often partnered with Sim2 projectors.
     
  6. Rob Sinden

    Rob Sinden
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 30, 2005
    Messages:
    2,588
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Newbury
    Ratings:
    +2,037
    What's the correct way to measure brightness, I've heard some very mixed reports depending on who you ask?
     
  7. Liam @ Prog AV

    Liam @ Prog AV
    Well-known Member AVForums Sponsor

    Joined:
    Oct 18, 2002
    Messages:
    8,498
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    136
    Location:
    Kent
    Ratings:
    +827
    Well ANSI Lumens is a measurement of total light output, so is useful for roughly comparing projectors when looking for a certain brightness projector. It is also an important figure in calculating contrast ratio - ANSI @ full white, divided by ANSI @ full black equals overall contrast ratio. How manufacturers come to these figures is a totally different story (such as not calibrating the projector for realistic skin tones, just calibrating for max white etc).

    Foot lamberts is a bit more specific as the mathematic of the screen size and surface is taken into account. The figure represents the amount of light reflected back per square foot so also by definition is taking into account the ambient lighting in the room (which should be blackout and not a factor). So basically where ANSI tells you what the projector is throwing out, lamberts tell you what brightness level you are actually seeing reflected back from the screen.

    Lamberts is supposedly the better measurement if you were trying to compare images by referencing them to numbers. But here is the crux of the thing, it is very easy to manipulate a projector to achieve very high contrast figures, ft lambert readings, lux, ANSI, whatever, but the side effect is an otherwise awful picture (gamma all out, colour wildly inaccurate etc). So I would try to steer away from the facts and figures and get more into actually seeing a couple projectors in the flesh. What their picture does for you in terms of all the factors you can't measure: image detail, feeling of depth, smoothness of image, colour accuracy, black/contrast detail etc. And of course how loud it is, what throw it requires, connectivity, upgradeability and so on. Sorry to get a bit preachy!! Just wanna make sure you don't go out a buy a projector by spec sheet only to actually be disappointed by it.

    Oh you've also got Runco's CSMS (Cinema Standards Measurement System) which is really a selection of rules to adhere to. The projector is rated in ft lamberts, but only once it has been set to correct colour temperature, gamma, brightness etc. This removes the ability for a manufacturer to for example max the colour temp for ANSI readings, then for measuring zero lightoutput to minimize the colour temp and lower the brightness level right down thus exagerrating the figures immensely. With CSMS standards reached, you can then measure for ANSI contrast and have a slightly more meaningful figure for comparison. Generally speaking Sim2 measurements are of this sort, they are minimum figures achievable with the projector properley calibrated for Home Cinema use.
     
  8. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    14,011
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,808
  9. Rob Sinden

    Rob Sinden
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 30, 2005
    Messages:
    2,588
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Newbury
    Ratings:
    +2,037
    Hi Liam

    Thanks for the insight.

    Is anyone doing comparative measurements then?
     
  10. Gary Lightfoot

    Gary Lightfoot
    Distinguished Member

    Joined:
    Apr 6, 2001
    Messages:
    12,464
    Products Owned:
    1
    Products Wanted:
    1
    Trophy Points:
    166
    Location:
    Surrey. UK.
    Ratings:
    +2,114
    A rule of thumb for many projectors is to reduce th advertised lumens by approx 40%, and then you will be in the ball-park for real lumens. It's by no means a definitive answer though and measuring is the only way to get close to accurate figures.

    An easy way to find the lumens coming from the projector is to buy a light meter and place it against the screen aimed at the projector and read off the number of lux. Multiply the number of lux by the area of the screen in square meters and that's the lumens coming from the projector.

    Ideally, and at a minimum, you'll want to have set the white and black levels first. An ISF calibration would be better still before taking the readings so that they will be at D65. This is the only time when readings really mean anything.

    Divide the lumens by the square foot area of the screen, and multiply by the gain and that would be the amount of foot lamberts.

    Cheap light meters can be bought from ebay for around £12 plus delivery, but I don't know how accurate they are.

    Gary.
     

Share This Page

Loading...