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Projector Aspect Ratios

There are about as many different opinions about video projectors as there are video projectors. There are so many different kinds, it can be hard to make sense out of it.

I’m not going to discuss business projectors. This is for the home theatre enthusiast who is looking for their first real projector. Business, sanctuary, and other application are discussed elsewhere in this section.

So let’s start with the basics:

4:3 or 16:9?

These numbers reference the native aspect ratio of the projector: NTSC (4:3) or widescreen High Definition (16:9). The first number refers to the width of the projected image, and the second, smaller number, to the height. These numbers define a relationship – for every 16 inches wide, the screen is 9 inches tall, for example. Substitute feet, millimetres, whatever you’d like – you still define a rectangular box. You may also see aspect ratios as a number, say, 1.33 for NTSC. Divide 4 into 3 and you get 1.33. Same for 16:9. It’s also referred to as 1.78.

4:3 is what we are used to watching. More square than rectangular, it provides for limited vistas. The infamous term “pan and scan” is derived from floating a 4:3 window over a widescreen movie. You don’t see the full picture.

16:9 is a convenient dimension for a display. It provides for a more panoramic scene, and allows directors more territory on-screen. Most DVDs are now encoded for widescreen (16:9 and up!), and all HDTV is 16:9. Get used to it folks. It’s here to stay.

Any decent projector will switch between 4:3 or 16:9. So that takes care of that, right? No. A 4:3 projector switches to 16:9 by turning off pixel rows at the top and bottom of the picture. I won’t bore you with the math, but your 4:3 projector set for 16:9 is working at about 2/3 of its optimal brightness and resolution. That’s a problem. Widescreen material, like HD and DVD movies, are made and transmitted at much higher resolutions than 4:3 is capable of, so when you want the best picture, you’re using only 2/3 of what the projector was is capable of.

The same is true when watching 4:3 material on a native 16:9 projector, but because 4:3 source material (“actual” pixels 640x480) is a lower resolution than 16:9, the only thing you really lose is a little brightness. Considering that 4:3 is on the way out (really out, not out in a Paisley shirt kind of way), it’s an acceptable sacrifice.