Over the next few weeks, as time presents itself, I’m going to put pen to paper in the hope to expand the knowledge of any client who wishes to know more on how to select a projector and screen thats right for your application.
Of course, if you cant be bother with the read please call us so we can point you in the right direction.
One of the first questions, that oft times comes about when discussing a potential projector purchase is “whats going to be the main use for the projector and what light levels are within the room.?”
Other determining factors for recommendations would relate to the budget, the room dimension and where you will be seated for viewing.
Before we go into the technologies that drive the projector hardware such as DLP, LCD or LED, lets first cover off some basics to bring you up to speed in what you will read in the Manufacturers spec sheet.
WHAT BRIGHTNESS IS REQUIRED WITHIN A ROOM
Brightness with all projectors is measured in Ansi Lumens. However, a Manufacturers spec sheet sometimes has video optimisation incorporated into their ratings and others do not, which means you could have a projector officially rated at say 1500 lumen actually brighter than models rated at over 2000. There are also other factors that determine the illumination your eyes perceive and these are the reflectivity of the screen and the projected image size (which has a relationship to the projectors throw distance).
For simplicity lets use the below table for whats accepted in the industry
• For a dedicated Home Theatre room (good blackout curtains) – look for a projector in the 1500 to 2500 lumen range, not below 2000 for 3D viewing, as the glasses take away from the levels of luminosity. By dampening down on brightness a dedicated home theatre projector can improve characteristics such as contrast ratios to give depth and detail to video.
• Education and business – look for a projector outputting between 2500-5000 lumens. Lower levels of brightness can be used, however, the ambient light in the room will need to be lowered to allow for a clear image. Also, for large screens; greater than 120″, 3000 lumens minimum is recommended to reduce faint or washed out imagery.
• Multi use – as you can see from the above, the determining factors for the required lumen output are mainly due to how much light is within the room and the size of the projected image. There is a relationship between light output and contrast of an image. Meaning that if you are needing the lumens to overcome ambient light you cant expect the same crispness to an image that a dedicated home theatre low lumen projector will be producing.
The biggest consideration for brightness of a projector is how far away it is to be mounted.
Remember in Physics the Inverse square law of light ..? Namely “The intensity of light is inversely proportional to the square of the distance. This means that as the distance from a light source increases, the intensity of light is equal to a value multiplied by 1/d2″
This in simplicity, means that if you half the distance, to where the projector is mounted you x4 the intensity.
Also, the larger the screen the more spread out the pixel concentration of light. Please, do not go too big with the screen, unless you have done the appropriate research.
WHAT IS CONTRAST
Contrast is the difference in brightness between the brightest and darkest parts in an image. The greater the difference, the higher the contrast.
Projector manufacturers within their spec sheet give a contrast ratio, however, like any sales tool, these numbers are sometimes artificially tweaked to give the consumer a false understanding of what the projector can really achieve. In general, a DLP projector will give a higher contrast ratio than an LCD. A high-contrast projector produces imagery with deep blacks and clearly defined shadow detail – giving depth to video images.
Without going into detail of the differences between On/Off contrast and ANSI contrast, the contrast ratio should not be looked at as the indicator of what projector to purchase as they can be highly misleading.
There is no set standard that Manufacturers need to adhere too within the stating of the contrast ratio and so dont put to much belief in what these numbers actually mean.
SETTING UP A ROOM
To produce the perfect room, non reflective walls and ceilings would be part of the setup – as any ambient or reflected light will reduce the contrast and make blacks appear more of a darker gray. For most, taking out the black paint and painting the walls and ceiling is a no go zone and so a reduction in the amount of light allowed to enter the room is of higher importance. High contrast grey screens also are there to assist in image quality where light is of a concern.
DRAW UP A PLAN OF THE ROOM
By measuring the home theatre room an understanding of the what size screen and where you “should be seated” for best viewing can be understood. For example with 2D viewing if positioned too close to the screen certain flaws of projector may frequent themselves – such as the fly-screen effect associated with an LCD projector.
SO HOW BIG SHOULD THE SCREEN BE?
Most projector manufacturers have on their site a projector throw distance calculator for yourself to work out at the maximum and minimum distance the projector must be positioned to fill the dimensions of a screen.
Before we look at this, lets discuss minimum and maximum viewing distance, as this will directly impact on the size of the screen for your room.
The minimum viewing distance is the closest distance to the screen one can sit before losing the ability to see the picture as a whole and once closer than this the human eye cannot capture the picture as a whole and will be continually scanning the screen in segments to take it all in.
The minimum viewing distance is generally about 2 x the width of the screen.
The maximum viewing distance is the farthest distance one can be from the screen to be able to comfortably capture the image.
The maximum viewing distance is 6 x the width of the screen.
What about for 3D – what is the “immersion zone” – the depth of zone within with the 3D effects reside.
I found many an article discussing 3D and 2D TV viewing and thought that this would be good reference material for a projector and screen setup.
The optimum 3D TV viewing distance most experts agree is in the vicinity of 1.4x to 1.6x the screen width. An interesting read on how screen resolution and aspect ratio effects the immersion can be found at
http://www.practical-home-theater-guide.com/3d-tv-viewing-distance.html
It also must be noted that “an immersive 2D TV viewing in the home theater, THX recommendations translate to a viewing range that varies between 1.54 to 2.2 times the screen width for a 1080p HDTV” and ” should reside at approximately 1.4 times the TV screen width for a 1080p screen.
Another article that i found of interest, is where they compare a person with 20/20 vision being able to “distinguish something 1/60 of a degree apart. This means 60 pixels per degree, or 32.86 degrees for a 1080p television”.
They can from this produce a chart to show the optimum viewing distance in relation to the size of the TV and also the resolution ”
http://www.rtings.com/info/television-size-to-distance-relationship
The aspect ratio of the projected media will also have an impact on the viewing distance, as it can be seen that going from say a 4:3 aspect ratio to a 16:9 ratio with the same screen width – the eyes have alot more pixels to absorb with the widescreen setting.
WHAT SCREEN SIZE IS BEST..?
As mentioned previously, the minimum viewing distance is generally about 2 x the width of the screen. This could be slightly closer for 3D viewing, however, if the screen is too large for the viewing distance, eyestrain, fatigue, headaches, and a desire to take breaks or stop watching the picture could result. The last thing you want is to get weary of your own home theater because you overdid the screen size.
Although most will find comfort at closer distances to the screen a suggested starting point would be to position yourself at 2.4 times the diagonal dimensions of the 16:9 screen and go from there.
You may also wish to use past experience at the Cinema, to give a gauge to how close you would like to sit – do you like the front couple of rows or maybe you’re generally seated midway…
A tip, that I give clients is, before you purchase a screen maybe you can use a ladder to put the projector in its rough position and use a sheet or a painted white wall to mimic the screen.
From this, and can experiment with immersion depths for both 3D and 2D viewing.
I also advise not to go larger than a 120″ screen, as the crisp image is now on its limits before becoming grainy and washed out – of course once 4K media and players come on the market this will no longer apply.
The old adage of “bigger is better”, unfortunately, does not run true with the selection of a screen.
AUSTRALIAN PROJECTOR SCREENS
What screens do Kickstart recommend ?
Now that depends on your budget.
The 3 main market leaders in Australia at this time are
Grandview, Screentechnics and LP Morgan – of course, Kickstart Computers sells all three ?
There are other brands too that we on-sell, however, our sales numbers dont drive us to mention their names within this discussion.
NEXT WEEK – we will look at the above three screen Manufacturers in detail.
CHEERS ANDY..