If you are like a lot of folks getting into projectors for the first time, you may be confused by the fact that every projector has TWO separate specifications for resolution: nativeand maximum. Why two different specs, and what is the difference between them?
It is actually pretty simple. Every projector that uses microdisplays, whether they are LCD panels, or DLP or LCOS chips, has a fixed array of pixels on those microdisplays. That fixed array of pixels is known as the native resolution of the projector. So native resolution is the actual, true, physical resolution of the projector. The projector will never be able to display more actual pixels than it has on those panels or chips.
So then what is maximum resolution? Well, that number has nothing to do with the projector's physical display. Instead it has to do with signal formats. Computer and video signals come in a wide variety of resolution formats. And every projector is programmed to recognize many of those different signals. Maximum resolution is the highest resolution signal that the projector has been programmed to process and display.
Converting non-native signal formats to native resolution
When a projector gets a signal that does not match its native resolution, it must convert that signal to the format of its native resolution in order to display it properly. This conversion process is commonly referred to as scaling.
So for example, let's assume you have a video projector with a native resolution of 1280x720 that is capable of displaying an HDTV 1080i signal. That means that the projector's physical pixel matrix is 1280 pixels wide by 720 pixels in height. However, each frame of video in an HDTV 1080i signal contains 1920x1080 pixels, which is a lot more than the projector has on its physical display. So in order to display the 1080i signal the projector must compress it into a 1280x720 format. It can do this because it has been programmed to do the compression from 1920x1080 to 1280x720. Furthermore, if 1920x1080 is the highest resolution that your projector has been programmed to recognize and compress into its native display, then 1920x1080 is known as the maximum resolution of that projector.
Sometimes the incoming signal format is smaller than the native resolution of the display. For example, let's assume you have a native XGA resolution projector, and you are displaying a standard NTSC television signal. In this case, your projector has a native 1024x768 pixel array. But a regular NTSC television signal is only 640x480 pixels. So the projector must "scale" or expand that television signal up from 640x480 pixels to 1024x768 pixels in order to display the image full frame.
Conversely, in our previous example, we talked about converting a larger 1920x1080 signal into a smaller 1280x720 display. Technically speaking, that is known as compression since you are compressing the signal to fit the display. However, it is less common to use the term compression these days. In typical usage, the term scaling refers to any conversion of a data or video signal to a projector's native display format, whether it is being scaled up (expanded), or scaled down (compressed).