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We’re often asked by customers why some projection screens have borders and some are just all white, which screen ratio should be considered?
Overhead Projector Images
In the old days, all portable projection screens in schools, colleges, universities and in the office, were effectively roller-blinds with an all white surface, and these did a fine job. When one remembers how they were used however, they were pretty-much used for the Over Head Projector (OHP) or for cine projectors. The plain white screens, those without boarders are perfect for OHP projectors as the projected image is effectively square. The shape of the square projected image is of course generated from the light-box onto which the OHP transparency is placed. OHP Projected images are referred to as having an Aspect Ratio of 1:1.
Along came the multimedia projector.
With the launch of the original multimedia projectors, their projected image mimicked TV broadcasts or VGA computer screen Aspect Ratios, i.e. 4:3 or as many people still call it, the old ‘squarer’ TV screen ratio.
Until the launch of widescreen TVs some 15 years or so ago, the 4:3 Aspect Ratio was the default screen ratio for everything, whether it was for broadcast TV or computer generated, even when the higher computer resolutions became more established, they we still projected as 4:3 ratio, even though to be absolutely accurate, they were really 5:4 ratio. I know it’s a little pedantic, because most people had no idea the Aspect Ratio of higher resolution SXGA was 5:4 and not 4:3.
..and then came widescreen
In the 1990’s broadcasters and screen hardware manufacturers decided to change the shape of screen images, this was to reflect more closely how they human eye sees the world, and how films were being projected in movie theatres. A new screen ratio was launched, this was 16:9, although not the same ratio that films were shown in theatres, it was closer to it than the old 4:3. In cinemas, the image can be much wide than even the widescreen TV 16:9, some are as wide as 2.31 : 1.
So practically, what does this actually mean?
As it does get complicated and there are traps to fall into, the following is a very brief practical guide.
If your main use of a screen is for an OHP use, then choose an all white screen or one that shows its’ Aspect Ratio as 1:1. If you’re using several projectors or if you’re not sure of your projector’s capabilities then the plain white or a 1:1 screen ratio screen is ideal
If you’re using a multimedia projector from a computer source, unless your projector states that it is has a widescreen function, then choose a 4:3 Aspect Ratio screen.
If you know for sure that your multimedia projector and the video source is widescreen, then of course choose a 16:9 Aspect Ratio screen.
Why choose any screen with a narrow black border?
All Aspect Ratio screens can be supplied with or without a narrow black border, whether it’s a 1:1 (OHP), 4:3 or 16:9, this narrow boarder has nothing to do with the aspect ratio, it’s more to do with aesthetics and improving the projected image.
If you think about it, you can’t project ‘black’ light, so when you look at a projected image, a black part of an image is where the projector is not firing light, so what you’re ‘seeing’ is the white projection surface. It sounds bizarre, but it’s true, the brain and the eye interpret the actual none-projected light area as black.
The black border on a projection screen is an old trick to give the eye a reference-point for black, it helps the eye to interpret colours to produce more in-depth and richer colours.
And finally, It also makes the screen look very smart!
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