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Projection Brightness

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There is more to image quality than just resolution. Brightness uniformity is also important. Uniformity is the percentage of brightness carried from corner to corner and edge to edge of your image. A higher uniformity rating means better consistency throughout your image. For the most consistent images, look for a uniformity rating of 85% or better. Brightness is measured in a number of way, most commonly ANSI lumens.

 

Measurement

 

Lumens: A unit of measurement of the amount of brightness that comes from a light source. The standard lumen rating of a data projector is the average of photometer readings at several points on a full white image on the screen. Technically, lumens measure "luminous flux." A wax candle generates 13 lumens; a 100 watt bulb generates 1,200. All of the specifications on our site are in ANSI Lumens, ANSI or American National Standards Institute is a standardized measurement system that can be used to compare projectors.

Foot-lambert: Measurement of light emitted or reflected from a surface. The higher the rating, the brighter the picture. One foot-lambert is equal to the reflected light radiated by one candle over a one-square-foot area.

 

Lux: The International System unit of illumination, equal to one lumen per square meter. Also called candle-meter (cd/m²), Primarily used for projectors with lower lumen output.

 

LUX =
Projector Light output (ANSi lumens)
x reflective Screen gain
-------------------------------------------
Screen area (square meters)

 

 

Luminance Abbr. Example
0.00005 lux 50 µlx Starlight
1 lux   Moonlight
400 lux   A brightly lit office
400 lux   Sunrise or sunset on a clear day.
1000 lux 1 klx Typical TV studio lighting
32000 lux 32 klx Sunlight on an average day (min.)
100000 lux 100 klx Sunlight on an average day (max.)

 

 

In order to select how bright a projector you will need, three factors need to be considered::

  • Room brightness (ambient light)
  • Screen size
  • Type of presentation

How Bright Should Your Image Be

"Sufficiently bright" has been defined by Society of Motion Picture and Television Engineers (SMPTE) in standard 196M as 12-22 footlamberts (41 - 75 cd/m2), though often 16 footlamberts is taken as the nominal goal.

However, this standard was developed for movie theaters with full light control. In a room with ambient light, this level of brightness may be insufficient. As a comparison:

  • CRT TV measures approximately 50 footlamberts (200 cd/m2) [and peak luminance can be much higher],
  • LCD TV approximately 117 footlamberts (400 cd/m2), and many Plasma TVs approximately 175 footlamberts (600 cd/m2).
  • A cloudy day outdoors is about 100 - 300 footlamberts.

It should also be noted that the eye's sensitivity to colors is strongly correlates to brightness, Hence, increasing the brightness of the image gives it a more vibrant look, thanks to the better perceived colour saturation.

Room Brightness

 

Firstly I'd like you to consider why commercial cinemas are dark? Its because even the brightest commercial projectors and TV's for that matter, Do not like light! No matter how much money you are willing to spend if you want to improve your image greatly, reduce the ambient light. This will maximize your projectors potential and allow you to use a lower lumen projector and achieve the same result. the other positive is that most high lumen projectors have a shorter lamp life around 1000Hrs.

Many sales staff say "You can watch it in daylight" Ok yes you can, but  Lumens or brightness can only help the bright part of the projected image, blacks in the image are not projected, light is switched off. If you watch in daylight the dark areas of the image which are not projected will look grey and washed out. If you have no option but to project in a lit room, you will need the extra brightness and a higher contrast ratio. If your room is very well lit, such as full fluorescents, you will need more lumens. If the room were to have half of its ambient light, you would need half the lumens. Rooms with minimal lighting will require a far less powerful projector which saves you money.

 

Screen Size

 

The bigger the screen, the more lumens you will need. If you double the screen size - say from
60 in. diagonal, to 120 in. diagonal, you will need a projector with 4 times the brightness. If you think of a torch shining on a wall the larger the beam the lower the brightness. So a good idea is to work out the size of the image you want. This is not just as big as the wall. As a rough guide remember that you should be at a distance from your screen less than 1.5 times its diagonal for that real cinema feel.

 

Type of Presentation



If you are presenting photos or other images where colour accuracy and contrast is important, (i.e. architectural images) you will also need a projector with more lumens. Its also important to consider the size of the room - the area that the light will be spread over when it leaves the screen. Larger the audience the brighter the projector.

 

Brightness of projectors:

  • Less than 1000 lumens - these are bottom of the lumens range and they are typically LED Projectors. If budget is an issue there are many projectors in this range. At this level image size has to be small and ambient light has to be kept very low.

  • 1000 to 2000 lumens - Most projectors in this range are for Home Cinema. 1000 lumen machines are suitable for normal movie and gaming projection use, closer to 2000 Lumens would be recommended for 3D projection. Ambient light should be reduced to improve image contrast, although complete block out is usually not necessary depending on the image size.

  • 2000 to 3000 lumens - this represents the high-performance range of the portable and semi-portable projectors. Products in this class are suitable for large conference rooms and classrooms. They offer more flexibility in terms of ambient room light, since the image is bright enough for some ambient light without washing out the image. They also offer more flexibility in terms of audience size since they can illuminate a larger screen without much loss of image quality.

  • 3000 lumens and up - the ultra-bright projectors are in several performance classes unto themselves, ranging from 3000 up to 12000 lumens or more. They are used in a variety of large venue applications, including board rooms, conference rooms, training rooms, auditoriums, churches, concerts, nightclubs, Simulators and so forth.


How bright should your projector be for your room?


Below is a fast and easy reference for you to use to help determine how bright a projector you need for your room.

 

  Zero ambient light- dedicated room
  Slight ambient light, dimmed lights, Curtains or blinds letting in light.
  High ambient light- enough light for people taking notes

 

           
4:3 Screen
Brightness Lumens Screen Size

72"

100"

120"

150"

180"
800    
1000          
1200          
1400          
1600          
1800          
2000          
2200          
2400          
2600          
2800      
 
3000        
 

 

We recommend the following lumen outputs:

 

 

Installation
Brightness
Lumens
Resolution

Hall / Commercial Cinema

12000
HD (1920x1080 dots)

Fixed

5200-10000
UXGA (1600x1200 dots) - XGA (1024x768 dots)

Portable

2500-5000
XGA (1024x768 dots) - SVGA (1024x768 dots)

Ultra portable

2000-3000
XGA (1024x768 dots) - SVGA (800x600 dots)

Micro portable

2500-3500
XGA (1024x768 dots) - SVGA (800x600 dots)

Home theatre

1000-2200
Wide-XGA (1366x768 dots) - SVGA (800x600 dots)

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