Projection Training at InfoComm
May 27, 2014 10:20 AM, With Bennett Liles
And how does keystone correction affect the sharpness of the projected image?
Actually keystoning is a projection purist’s nightmare. Ideally you really want to be straight up to the screen and when you tilt the projector, you’ll definitely see some degradation because the image is created from millions of square pixels and when you shoot straight on the pixels maintain their square shape. Any time you project at an angle, the little squares become trapezoidal and they’ll distort your image. In simple keystone correction where a line is originally straight on one column, to correct it there’s pixilated stepping that occurs on a straight line over multiple columns. You’ve probably seen this when you’re playing around in Paint or something like that or where you’re just bending a line on your computer, so it’s creating a straight line over multiple columns. Then there’s a process that occurs to smooth those lines where it displays two pixels at half brightness instead of one pixel at full brightness. As a result, it can visually make that horizontal line look like spun twine. The same thing for a vertical line, with vertical keystone. [Timestamp: 5:46]
When I put just one little unit of keystone correction into a projector I can immediately see the image get softer.
Oh, absolutely. It’ll make it more blurry because it’s trying to typically smooth those lines. And it’s definitely going to be a lot more prominent if you have an image with horizontal or vertical lines and it’s keystoned in that orientation. [Timestamp: 6:04]
And you can have a very good projector just having to fight the ambient light in a room that’s poorly lit for projection. That can be a big factor, just having the right ambient lighting.
Right. Ambient light is actually really important when you’re calculating the target brightness of a projector and the application. So extra light in the room means that there’s gonna be more light on the screen and it can make an image look much more washed out. So you really want to account for all the light in the room when you’re spec-ing in a projector. A lot of times there’s also a screen material that’s made specifically to enhance your image and your application, so while in your case you may use a different projector, you could use different screen types to actually make the image look much better. [Timestamp: 6:43]
One of my pet peeves with the facilities people is that they don’t have separate lighting controls near the classroom podium so that you can, from there, just control the lights right in front of the screen. Just something as simple as that could make it appear as if you have another couple of thousand lumens from the projector.
Oh, absolutely. If you can turn any lights off near the screen then you’ll get a lot more light reflected off of the screen straight from the projector. So any light in the room really reflects it.
Yeah, I’m sure ambient light is often overlooked when planning rooms for projection or just retrofitting a room with a projector. Now you talk to a lot of people and you conduct these courses. What in your experience is the most misunderstood aspect of projection technology? What do you get the most questions about?
Honestly, signal distribution. So this actually comes from my experience working with our applications engineering group. So if the signal isn’t strong enough to get to the projector, it won’t display it. Sometimes it’s the quality of the cables or the length of the run or the processor in between the source and the projector – something that’s causing the signal to weaken so much that the projector won’t accept the signal. Many times signal degradation is due to the impedance mismatch that can be aggravated by longer cables. So some displays, like flat panels, they have a higher threshold in accepting weaker signals and they might display the image which isn’t really a fair test to determine the projector’s functionality and if the projector is actually failing at this point. A high-performance projector needs a high-performance signal and a lot of times that signal isn’t strong enough to get to the projector. [Timestamp: 8:17]
And what do you look for in rating screen material? You get all kinds of surfaces being used, including walls. What do you look for in rating the kinds of materials that you’re going to use for the surface of the image?
Screen manufacturers make materials to fit all kinds of applications so if you’re in a dark room, again with controlled lighting, a unity gain screen, which is usually white, would be best. If your application calls for overhead lights like we spoke of before, then you may want to look at a low-gain screen, usually gray in color, that will absorb a lot of the light making those colors look a lot more rich and not washed out. There’s also angular light rejection screens made of layers and ridges that reject overhead light reflecting back to the audience and on the screen. And then there’s perforated screen material that allows you to install speakers behind the screen to let sound easily travel through the perforations. So some factors to keep in mind when you’re spec-ing in a screen would be ambient light, sound design, audience size and intensity of the light hitting the screen. There’s not actually a one-type-fits-all kind of screen. [Timestamp 9:17]
Well, there’s a whole lot to this, a lot more than people tend to think about until they really get into it so a lot of people are coming to your courses at InfoComm. Those are going to be Understanding and Designing Warp and Blend Applications and the other will be Solid State Illumination and Projection Technology 101 and I think it’s going to be a full house.
Yeah. Last year we had some full houses for every class. We were packed out. We have some new content. We have a new laser projector coming out this year so I’m trying to focus more on our solid-state illumination and get that information out there. There’s not another three-chip laser projector on the market right now, so we’re kind of taking a turn and actually teaching people about the technology. [Timestamp: 10:00]
It’s going to be interesting when the people get to talk to you face to face and ask their questions. Thanks Erica for taking the time out to give us a preview of it. Erica Strickland, Training Manager for the Americas at Digital Projection. I know you’re going to have a great show this year.
Absolutely. Thank you so much, Bennett.
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