First – the home theater has total light control. In order to get really low black levels and a high contrast image you must eliminate virtually all sources of light except for that coming out of the projector. If your screens appears white or grey with the projector turned off and with the room lighting as you have it for movie viewing, then that is as near black as you will ever see once the projector is turned on. Just remember that projectors can project light and they cannot project dark.
Second – the home theater has wall and ceiling painted a dark color in order to reduce light being reflected back toward the screen.
Now let’s get into the most important characteristics for projector and for screens necessary to achieve and adequately bright image in your home theater. Projector’s Light Output My first golden rule for projectors is to never assume the lumens listed in the manufacturer’s specification sheet has any relationship to reality for using that projector in a home theater application. Just about all projectors will have a mode that is intended to provide the maximum possible light output. This mode may be called such things “dynamic” or “vivid” and while it usually will produce a lumens output near that specified by the manufacturer for that model of projector, this mode is normally not suitable for use in a home theater environment. Such high light output is typically achieved by sacrificing accurate color, grey scale, color temperature and black level. Some projectors when properly calibrated for critical viewing may produce a lumens output of perhaps a much as 80% of the lumens in the maximum brightness mode. However, other projector may produce less than 30% of the manufacturer’s specified lumens output once calibrated. So the bottom line is you need to find out what is the actual light output of the projector you already own, or are considering to purchase. One good way to do this is to read the reviews Art has posted here on Projector Reviews where you will find out what were the actual measured lumens once the projector was calibrated to the D65 video standard. One other point to consider is the lamps used in video projectors (not applicable for those few projectors that use LEDs instead of a lamp) will dim with use. A decrease in light outputs of 25% to 30% is typical during the first few hundred hours of use and the rated life of a bulb (specified by the manufacturer in hours) is for when the bulb is predicted to lose 50% of its original light output. Therefore, a projector that is measured in “best mode” to put out, for example, 600 lumens may only put out perhaps 450 lumens after 500 hours of wear on the lamp and eventually only 300 lumens as the bulb approaches what the manufacture considers the end of the bulb’s life (typically somewhere between 2000 and 4000 hours). So it is a good idea to assume at least some bulb dimming (e.g., 30%) when attempting to forecast how bright an image you can expect with a specific projector and screen combination. Also another factor to consider when reading reviews of projectors is to note where the projector’s zoom lens was set, or if the projector was position for short, mid, or a long throw distance. A projector’s zoom lens will normally have greater light loss when set for a long throw distance vs. when set for a short throw distance. Or expressed another way, a zoom lens will have more light loss when set to it maximum focal length (i.e., min. picture size) vs. when set to minimum focal length (max. picture size). Projectors having a wide ratio zoom lens (e.g., 2X zoom) will normally have a greater change in lumens output over the zoom range as compared to projector with a more limited zoom range (e.g., 1.2X zoom). Most projector measurements provided here at Projector Reviews will have the zoom lens set to a mid-throw position but will provide information to indicate how much the light output will increase at shortest throw and how much the light output will decrease at longest throw. So you will need to determine for a given projector and screen size if your mounting location for the projector will place it at a short, mid or long throw position. Some manufacturer’s web sites provide a projector setup calculator that will show the throw range supported by the projector’s zoom lens for a given screen size and/or you can download the owner’s manual which will have a section on the projector setup/installation that will provide the required information. The table below shows, for a few popular projector models that have been reviewed here at Projector Reviews, the manufacturer’s specified lumens and also the measured lumens in high lamp mode once the projector was calibrated for the most accurate colors, grey scale, etc. (ie., the “best mode”) as well as info on the projector’s zoom lens ratio. All of these lumens measurements were performed with the projector positioned at a mid-throw distance. See the full review (click on the projector model) for the complete set of measurements.Projector Model | Rated Lumens | Zoom Ratio | Calibrated Best Mode Lumens |
Epson Home Cinema 8350 | 2000 | 2.1X | 467 |
BenQ W6000 | 2500 | 1.5X | 866 |
Panasonic PT-AE4000 | 1600 | 2X | 430 |
Mitsubishi HC9000D | 1000 | 1.8X | 701 |
Sony VPL-VW90ES | 1000 | 1.6X | 588 |
JVC DLA-HD250 | 1000 | 2X | 758 |
- Estimated actual projector lumens output (from reviewer’s measurements)
- Screen size (aspect ratio and diagonal size in inches – HD format screens have an aspect ratio of 1.78 (to 1) while “scope” screen have an aspect ratio of approx. 2.4 (to 1).
- Estimate of screen gain for your primary viewing locations (from screen spec. sheet)
For 3D projection the effective lumens, when accounting for both the projector's light ouput but also subtracting for the light loss through the 3D glasses, will be far less than for viewing 2D video with the same projector. For 3D systems using active shutter 3D glasses the effective 3D lumens is typically about 20% as much as when using the same projector for 2D viewing. Therefore, it is generally a good ideal to increase the goal for the 2D brightness (from the screen) from 16 foot lamberts up to at least 25 foot lamberts so that when used for 3D projection there will still be at least an effective 5 foot lamberts available (also considering the light loss through the 3D glasses). I have attached an Excel spreadsheet file (below) that can be used to calculate the estimated image brightness, in foot lamberts, once you enter the above basic information. If you have Microsoft Excel (part of Microsoft Office) installed on your PC simply download and open the attached file with Excel. If your PC does not have Excel installed, you can download an Excel viewer from Microsoft . Just download and install the Excel Viewer program and then you should be able to open the attached spreadsheet file. Click to download the Excel spreadsheet >>>>> ProjectionCalc ______________________ For my next blog I will be discussing DLP projector technology for 3D