We initially covered aspect ratios back in the section Resolutions and Aspect Ratios Explained In this section, we will go in-depth about how projectors display different aspect ratios.
Scenario One. You are going to buy a widescreen projector and would like to know what to expect when using it to view non-native aspect ratios.
The first thing to understand when purchasing a widescreen home theater projector is that almost no content is actually in a 16:9 (1.78:1) aspect ratio. Therefore, almost all of the material you watch will be formatted to fit onto your screen (with black bars displayed on top and bottom or on the left and right of the image).
When watching standard definition television (4:3 or 1.33:1 aspect ratio material), you generally have the option of either watching the material in its native aspect ratio or stretching the image. Most home theater projectors will usually give the option of blowing up the image to fill the entire screen, thus cutting off some of the top and bottom of the image, or subtly stretching the image horizontally. And, both options have serious flaws: either you’ll chop off some of the image or you’ll stretch the image and cause image distortion. The best option is to leave the image alone.
Example 1 shows the difference between stretching the image horizontally versus leaving the signal as a 4:3 image.
Watching DVDs, or other material that is film-based, will result in your discovering that movies are seldom, if ever, filmed in a 16:9 (1.78:1) aspect ratio. Instead, they are generally recorded in a 1.85:1 or 2.35:1 aspect ratio, which is actually wider than the aspect ratios of widescreen projectors or televisions. When watching material in a 1.85:1 or 2.35:1 aspect ratio on your widescreen projector, your image will look like example 2.
Whenever a projector adds black bars to an image, you are no longer using the full resolution of your projector. If buying a widescreen projector, make sure to match the resolution of the projector to the resolution of the content you will most likely watch to ensure the best results.
If you aren’t watching HDTV often, and don’t plan on converting to it in the next few years, an 854 x 480 projector will suffice for watching standard definition television and DVDs as it most closely matches the resolution of DVD.
If most of your viewing is DVD and standard definition television, and you do watch some HDTV programming, a 1024 x 575 or 960 x 540 projector will give you wonderful clarity for both standard definition and high definition sources.
If you love your HDTV now and want something that takes full advantage of it, then a 1280 x 720 or greater resolution projector is what you need. But keep in mind that standard definition sources will generally look crisper on a projector that better matches its resolution.
Scenario Two. You are going to buy a 4:3 aspect ratio business projector to use for home theater and would like to know what to expect when using it to view non-native aspect ratios.
Mapping widescreen images onto a 4:3 projector can pose unique challenges and a consumer needs to be aware of them.
Micro display projectors all have a native resolution that can’t be changed. If you are buying a 4:3 projector and plan to watch widescreen images on it, you must understand that you are going to lose a significant amount of vertical resolution in the process. Let’s look at a native 4:3 aspect ratio 800 x 600 (SVGA) projector as an example.
If you watch a 16:9 (1.78:1) aspect ratio image on an SVGA projector, your total vertical resolution available drops from 600 lines to 450 lines as seen in Example 3.
If you watch even wider screen images on an SVGA projector, your vertical resolution drops even further. Example 4 shows a 2.35:1 image on an SVGA projector.
Problems can arise when you try to watch HDTV images on a projector with too low of a resolution. A 1280 x 720 image from a 720p HDTV signal would have to be scaled down to 800 x 450 on an SVGA projector. That is a staggering 61% loss of resolution! The situation would be worse when watching a 1080i HDTV signal.
Here is a quick table of the 16:9 (1.78:1) resolutions for common 4:3 aspect ratio business projectors. Remember: always choose a projector that best matches the resolution of the source material you watch the most.
An SVGA (800 x 600) projector is actually 800 x 450 when viewing a 16:9 image.
An XGA (1024 x 768) projector is actually 1024 x 575 when viewing a 16:9 image.
An SXGA (1365 x 1024) projector is actually 1365 x 766 when viewing a 16:9 image.