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Topic: video projectors spec info

Dave Ganoe
Expert Film Handler

Posts: 119
From: Point Marion, PA
Registered: Jun 99

posted 04-20-2004 07:15 PM

Got some questions about video projectors. Thinking of getting a new one with DLP technology and wondered if anyone has had experience with any that are based on DLP and around $1000. ALso would want it have a lamp that doesnt cost a fortune to replace. Is the higher the contrast ratio the better the picture? How is ansi lumens compared to watts in light output? I currently have an infocus lp570 and my screen is about 45 feet away. Does a nice job but want to upgrade to something better. THanks for any info.

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Adam Martin
I'm not even gonna point out the irony.

Posts: 3686
From: Dallas, TX
Registered: Nov 2000

posted 04-20-2004 08:00 PM

You need a visit to www.projectorcentral.com.

quote: Dave Ganoe
ALso would want it have a lamp that doesnt cost a fortune to replace.

Good luck. [Wink]

quote: Dave again
Is the higher the contrast ratio the better the picture?

Yes. The lower the contrast ratio, the lighter the blacks are and the more washed-out it looks.

quote: Dave yet again
How is ansi lumens compared to watts in light output?

Lumens is a measure of how bright something is. Watts is a measure of power consumption. A comparison of the two depends on the type of lamp used, as some lamps are more efficient than others. (A 40 watt fluorescent lamp puts out more light than a 40 watt incandescent lamp.)

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Gilbert Travin
Expert Film Handler

Posts: 101
From: Villeurbanne / France
Registered: Jan 2004

posted 04-21-2004 04:47 AM

Hi Dave !

If you get a dlp model, pay attention to the "rainbow" effect : if you are sensitive for this purpose, it will be quickly very unpleasant to show any video...
Modern projectors have a frequency of 300 Hz, but certain people are still sensitive at this frequency ...
You must test several projectors with several contrasted films ....

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 04-21-2004 02:46 PM

Doesn't the DLP projector "rainbow effect" really depend on scene content? I would assume a fast-moving black-and-white scene with lots of detail would be most prone to the color fringing.

http://www.extremetech.com/article2/0,3973,1153392,00.asp

quote:

One of the leading artifacts of DLP technology is color breakup, also called the rainbow effect. Fortunately, only a small percentage of people are affected by this artifact. I can see rainbows in images with a dark background and bright areas when I move my eyes quickly from point to point on the screen. It can be pretty obvious with fast eye movements when viewing certain black and white test patterns. The rainbow effect appears as a momentary flash of rainbow-like striping typically trailing the bright objects when looking from one side of the screen to the other quickly, or when quickly looking away from the TV to an offscreen object.

The rainbow effect is caused by light passing through a spinning color wheel with colors flashing sequentially.

http://www.audioholics.com/techtips/specsformats/displays_DLP_technology2.html

quote:
What is the Rainbow Effect? The DLP 'rainbow effect' is an artifact unique to single-chip DLP projectors. The artifact appears as a rainbow or multi-color shimmer briefly noticeable when changing focus from one part of the projector screen to another. It appears as a secondary image that appears at the viewer's peripheral vision and is generally noticeable when shifting focus from a high contrast area or bright object. For a quick video sample of the effect, click here (warning: 5MB video).

3-chip DLP projectors, higher wheel speeds, 7-segment color wheels, and archimedes color wheel designs (pending) are minimizing or may altogether elminate the effect.

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Bobby Henderson
"Ask me about Trajan."

Posts: 10973
From: Lawton, OK, USA
Registered: Apr 2001

posted 04-21-2004 06:27 PM

An additional feature I would be careful about in buying a DLP projector is resolution. Most lower priced DLP projectors made for any computer use top out at 800 X 600. You usually have to spend well over $1000 for anything 1024 X 768. The price will usually go well above $2000 for a projector using 1280 X 1024 DLP chips.

The spinning mirrors with DLP remind me of a cool trick I tried out in high school.

Make a traditional color wheel, with your six primary and tertiary colors (Red, Yellow, Blue, Orange, Green, Purple) evenly divided like pie slices across it. Cut the wheel out in a circle and attach it either to a circular saw blade or disc sander. Turn on the power tool. Color wheel suddenly appears as an off white color, just a little grey since your painted colors are subtractive and not additive in synthesis.

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 05-23-2004 04:48 PM

The single-chip DLP also has other tricks that make its specs better than its performance.

Like the spining wheel...they can (if not always) have a white segment to brighten up the picture. This of course, kills contrast but wont show up in a "pixel-on, pixel-off" contrast ratio that projector manufacturers like to use.

DLPs also use dither to help with their brightness graduations...as a result, they don't really have great greyscale resolution (or color depth)...this is the measure of different intensities of grey/color rather than the absolute black versus absolute white. It is one of the downsides of jiggling mirrors.

Another problem DLPs have is static pictures...if you look at a Powerpoint show on a DLP and again on an LCD...the LCD will do a better job. The DLP will have problems not making all the mirrors look like what they are doing...jiggling. The LCD, on the other hand, will put up a rock-steady picture. The down side is that as you approach the screen, it will have a "screen door" appearence. Another downside for LCD is that their colors are not stable. Measure one when new...measure it after some use...the colors will drift.

Steve

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Tim Reed
Better Projection Pays

Posts: 5246
From: Northampton, PA
Registered: Sep 1999

posted 05-31-2004 09:58 AM

quote:
The rainbow effect appears... when looking from one side of the screen to the other quickly

So don't move your eyes. [Razz]

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