If you are looking to buy a new projector and are comparing various models, you will notice that there are two different resolution specs: native and maximum. This is unlike, say, a TV screen or a computer monitor which has just one display resolution. Many first time buyers select a projector by looking at the maximum resolution value alone on the assumption that it is the highest image-resolution the device can project – which means better image quality.
But, this is not the case. In fact, it is the native resolution which determines overall clarity and sharpness.
What is native resolution and how does it differ from maximum resolution?
Every projector has an in-built micro-display (could be a DLP, LCD or LCOS) which has a resolution of its own. The number of pixels contained in this panel/chip is the native resolution of a projector. This hardware restriction means that there is no way in which a projector can display an image in a resolution greater than its native resolution.
The maximum resolution, on the other hand, has nothing to do with the projected image and refers only to the input signal. Every projector is programmed to recognize inputs in a variety of formats and sizes and the maximum resolution is the highest resolution value that the device can process and then display.
How does the projector handle a signal in a resolution other than its native resolution?
If the input resolution is higher (as high as the maximum) or lower than the native resolution, the projector will convert the signal to the native resolution using a process called scaling.
Imagine a projector with a native resolution of 1280×720 capable of handling up to 1080i HD signals. Without scaling, the projector won’t be able to handle 1080i content because the 1920×1080 resolution obviously has more pixels than the device’s micro-display which only has 1280×720 pixels. To display higher resolution content, the projector automatically down-scales (compresses) pixels in the input feed to its native resolution. In this example, if the input were 4K (4096×2160), the projector won’t work since its maximum resolution is only 1080i.
If the input is of a lower resolution, say, 640×480, the opposite scenario happens. This same projector will automatically upscale (expand) the content to fit into its larger native resolution of 1280×720.
Is there any downside to scaling?
The entire process of scaling is an exercise in approximation. The projector uses the pixel information in the input signal to figure out how an image would have looked if it were in its native resolution. The best it can do is to make sure that there isn’t a huge loss in detail or sharpness. If the input resolution is lower than the native, the output tends to look a bit soft and blurry. If the input is higher, the output may look a bit cramped. Thankfully, when it comes to video/image content, scaling engines have become very accurate these days and the output generally looks crisp and clear.