General projector help... what is contrast ratio, native resolution?

Question

I'm looking to get a front projector for my basement. I'd like to project a video immage on to my basement wall. I'm looking on-line at projectors and i'm looking at all of this stuff i don't understand. I just need a simple lamens terms explenation for the generic stuff.

Answer 1

Contrast ratio is a measure of the ratio between the lightest and darkest output possible ... the dynamic range of the picture.  The higher the better (although there are various ways it can be measured (full on-off, ANSI, dynamic) and some numbers are inflated, so be careful to compare similar ratings). See the 1st link for a good article on contrast.

Contrast is also the most important of four factors that determine perceived picture quality (others, in decreasing order of importance, are colour stauration, colour accuracy and resolution). A high contrast ratio is responsible, when present, for the "pop" or almost 3D look to a picture.

But anything more than 2000:1 is "destroyed" by ambient light, so don't go overboard to buy a bit higher CR since unless you view in a completely dark room you won't see any difference.

Another term you need to be concerned with is the brightness (normally measured in ANSI Lumens ... where lumen is the unit and ANSI is a standards organization that defines how brightness is measured). projectors are usually rated based on maximum light output (1000-1500 lumens is typical), BUT it is brightness of a properly calibrated projector that really counts ... and this is typically 300-500 lumens for a 1000 ANSI lumen projector. Unless you plan a huge screen (120" or more) or have poor control of ambient light, a 1000 lumen projector is fine.

The other main factor is resolution. There are two types of resolution: Native resolution, which is the number of pixels (dots) wide x the number of pixels high of the output from the projector; and, input resolution, which is the range of signal types (e.g. 480i, 480p, 720p, 1080i, 1080p) that can be accepted by the projector and output in the native resolution (after processing by the electronics in the projector).

The number (in 480i or 480p for example) refers to the number of horizontal lines (or vertical dots) that make up the image. The "p" and "i" in refers to whether the image is "progressive" (every line of the image is scanned sequentially), or "interlaced" (the image is constructed by scanning the odd numbered lines then going back and filling in the even numbered lines). This only applies to the input signal (output from your DVD player, cable box, etc), since all digital projectors display a progressive image.

Projectors fall in three basic classes: 480p, 720p and 1080p. The higher the number (basically it's the number of vertical dots that make up the picture) the more detail possible in the image, and the higher the cost of the projector. 720p and 1080p projectors are considered high definition models.

A few other numbers of interest: throw distance range (the range of distance the projector must be from the screen to give a certain sized image (usually 100"), fan noise level (anything less than 26-28 dB is fine for home use), aspect ratio (the ratio of the width to height ratio of the projected image. For movie/HDTV use most people prefer 16:9).

The 2nd link is to an on-line guide to some of the preceeding specifications.

There -- hope that helps.