Join Date: Feb 2001
Location: Kansas City, KS
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Yes, the pixel size is always the same on the projected image. The screen itself literally uses small glass beads to create a textured yet highly reflective surface. However, the distribution of the beads is random across the cloth, not in rows or ordered. The patterns the beads are in across the screen can interact with the d.p.i. projected on the screen. If the screen and projector were absolutely fixed (impossible), then my guess is the crawlies would occur in only certain areas of the screen where the two "resolutions" were interacting negatively. As both the screen and the projector are moved in relation to one another, the trouble spots will shift.
Believe me, I have seen this time and again - I am on staff at a large church which over the last three years has made the transition from overheads and slide projectors to all video projectors. Initially, the budget was created with the intent of using all the existing tripod mount screens - ten 7-12 year old screens, most of them glass beaded. We soon realized that the video projectors would NOT work well with the glass beaded screens, and began to replace them as well. Only a year ago I had our experiences confirmed at Infocomm by an installer who made the above statements about glass bead/projector resolution interaction. The same goes for old striped "silver lenticular" sceeens - moire all over the place! Anyway, I'm not a visual physicist, and not up to giving the numbers, ratios, and ocular anomolies that cause the problems - I just know they exist. As I said above, be of good cheer! I thought my projector was going bad when it developed some strange noise in the picture. Lived with it for a few weeks while contemplating a new projector purchase before realizing that the outlet had simply lost its ground somehow. After grounding the outlet and conditioning the power ($50), the image was perfect! Always start with the simplest (cheapest) solution. You may be surprised!
[This message has been edited by TSO (edited 04-20-2001).]