What is Resolution?
A projector’s resolution is a specification most people come across
when they are looking for a new projector. However, the various types
and definitions of resolution can make choosing a projector based on
its resolution quite confusing. It is important to understand the key
definitions of resolution since they can be a major factor in the final
quality of your presentation.
Knowing which projector resolution is best for you can help you to get
good value for money, and more importantly, to get the right projector
for your application. In this Bamboo AV advice section we will examine
each aspect of resolution, so you will be prepared when comparing
different projectors and their resolutions. We’ll start at the
beginning by explaining the definitions of native and maximum
resolutions.
Native resolution and maximum resolution
Projectors are called fixed-resolution displays because they have a set
number of pixels (the individual dots that make up the image) that
they can use to display images. For example, an XGA projector can
display a maximum of approximately 786,000 pixels. This fixed array of
pixels is known as the projector’s native resolution and is
determined by the type of internal LCD panels or DLP chip the projector
uses. Native resolution is the actual physical resolution of the
projector, and the projector cannot display more pixels than this.
Maximum resolution, on the other hand, has nothing to do with
the projector’s physical display. It is actually to do with the format
of the signal being sent from the computer or video source to the
projector. These signals come in many different resolution formats, and
each projector will be programmed to recognise several of these
signals. Maximum resolution is essentially the highest resolution of
signal that the projector has been programmed to process and display.
The different types of resolution: SVGA, XGA, SXGA and UXGA
You will probably have heard the terms SVGA, XGA, SXGA and UXGA
mentioned when referring to a projector’s resolution. These are the
main “standards” of resolution, and simply represent the various fixed
(native) resolutions of a projector's internal panel or chip, on which
an incoming signal must first be mapped before it can be projected. The
four terms above describe common resolutions used by computers and
projectors. The standards WVGA, WSVGA, WXGA and WUXGA describe common
resolutions used by Widescreen (16:9 aspect ratio) home theatre
projectors.
The table below compares these 8 standards:
Resolution
|
Pixels
(horizontal x vertical)
|
Total number of pixels
|
Notes
|
| SVGA
|
800 x 600
|
480,000
|
Popular due to attractive prices and good quality images when projecting simple graphics and presentations
|
| XGA
|
1024 x 768
|
786,000
|
Good for relatively high-resolution images from videos, detailed
documents and graphics. More expensive than SVGA but an equally popular
resolution standard
|
| SXGA
|
1280 x 1024
|
1,311,000
|
High resolution and more expensive than XGA. SXGA products are good
for command and control, engineering and applications where acute
resolution of small details is necessary
|
| UXGA
|
1600 x 12000
|
1,920,000
|
Used for very high resolution workstation applications that require
lots of detail or information. These are expensive projectors that
support a broad range of computer equipment
|
| WVGA
|
854 x 480
|
410,000
|
Known as 480p resolution. Used for home theatre systems and other widescreen applications
|
| WSVGA
|
1024 x 576
|
590,000
|
Known as 576p. The step up from 480p to 576p is generally not thought to be worth the cost.
|
| WXGA
|
1280 x 720
|
922,000
|
Known as 720p resolution. This is the resolution for true native HDTV.
|
| WUXGA
|
1920 x 1200
|
2,304,000
|
Full High Definition Resolution. Dramatic price increase from WXGA.
|
SVGA and XGA are currently the most common resolutions available. SVGA,
being of lower resolution (800 pixels wide x 600 pixels high), is less
expensive than XGA (1024 x 768), but doesn't provide sufficient
resolution to do justice to HDTV signals. Most new laptops are now of
XGA resolution
Scaling: Resolution compression and expansion
Most projectors can process information from sources with higher or
lower resolutions than their native resolution. To do this, when the
projector receives a signal that does not match its native resolution
it converts that signal into the format of its own native resolution in
order to display the image properly. This is called scaling, and
whenever it takes place there is always some loss of signal quality, or
“fuzziness”. If the projector is processing a resolution higher than
its native resolution (e.g. if you have an XGA laptop and an SVGA
projector), the image signal from the XGA laptop will be compressed into
fewer pixels. This means that some of the laptop’s pixels are shared
across the same pixel that the projector displays. With photos and
video this scaling is hard to detect, but with small text the
compression can cause noticeable losses in quality. This is where the
definition between maximum and native resolution becomes important. Just
because a projector can display a higher resolution, it doesn’t mean that it will display it well.
How does resolution affect picture quality?
A higher resolution projector generally means better picture quality,
especially on larger screens where higher resolution images will look
sharper and less block-like. This also means that you can sit closer to
the same screen without seeing the pixilation. Higher resolution
projectors will also be less likely to require signal compression and
its associated loss in quality. For example, HDTV signals will look
better on 720p projectors than 480p projectors.
Does higher resolution always mean a better image?
The answer is no, not always. For example, a DVD has 480 available
lines of video information. If you have a 480p projector, the image
quality will be very good. However, if you upgrade to a 576p projector,
since the projector cannot create additional picture information
beyond that which it gets from the signal, it will need to up-scale the
image and distribute it over 576 lines which can cause a loss in
sharpness.
So what resolution is best for my application?
To choose the right resolution for your projector, you need to know the
resolution of the video source or computer you will use with it. The
image projected will be the maximum quality if your projector
resolution matches your computer's resolution exactly, since then there
is no scaling to worry about. For example, if you normally use a
notebook computer with XGA resolution (and many new laptops are in this
format), you will want a projector with the same native XGA resolution.
If you will be using the projector with several different computers,
the projector should have a resolution as high as the highest computer
resolution.
For DVD, as we have seen, a 480p (WVGA) projector will do the job. This
resolution of projector will also produce very good images with
standard definition TV since this type of signal also has 480 lines of
video information. 480p will display acceptable picture quality from
HDTV signals.
For true HDTV, most people agree that upgrading from 480p to 576p is
not worth the money as this only produces a minor reduction in
pixilation and a slightly better HDTV signal. Upgrading to a 720p
(native HDTV resolution) projector is a more sensible choice to really
see the results of higher resolution, and signals from sources such as
Blu-ray and HD-DVD will also look much sharper.
We hope that this Bamboo AV advice section on resolution has been useful to you!
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