Angles Of View
Craig Park is Vice President, Integrated Solutions for Intellisys Group, engineered design/build systems integrators in Mountian View, CA which he joined in 1996, Prior to that he spent 10 years as Principal and the Director of Audiovisual Services for Paoletti Associates, Acoustical and Audiovisual Consultants in San Francisco, and 15 years designing audiovisual systems and facilities for the Hubert Wilke organization initially in New York and then as Manager of its Los Angeles office. A Fellow of the Society for Marketing Professional Services, Mr. Park has made numerous contributions to the education of our industry. He can be reached at firstname.lastname@example.org. He is interviewed here on the subject of
Planning a Visual Display - Getting it Right the First TimeDa-Lite: One of the many paths along which you must guide your clients as they seek to acquire a presentation system is the one that leads to Screen Selection.” What steps do you take to ensure that the very best available screen gets specified?
Park: First and foremost we insist that we talk specifically with the people who will actually be using the space for presentations. Very often in a designer’s daily life we are faced with clients (architects or end users) who are not in fact the people who will use the space being commissioned. As such they are not the people responsible for building the media to show the information they want to get across.
But if you can talk specifically with the people in the client organization who are building the content about the nature of that content and about what their expectation is for what they’re showing, you can create a successful facility. Because with that knowledge, you have the ammunition to go back to the architect or the facilities manager and say, OK, for this kind of data you need images of this size if they are to be readable by audiences that you have defined as the program for this project.
Da-Lite: Which formula do you use to size a screen?
Park: The formulas have been out there for years and years and you can argue whether or not 6w or 6h, 8w or 8h, 4h are the right formulas but I think ultimately it’s going to vary with the very specifics of the kind of data being presented. An accountant is going to be more likely to want to push the envelope because he’s going to want to show facts and figures at a scale much smaller than what one would normally want to design for. But if you want to accommodate him and if he and his staff constitute the group that’s going principally to use the room then you have to make the argument to whoever’s in charge that this room will not function to anyone’s expectation if you don’t accommodate its users. When the politics of the situation prevent you from talking with the real users of the system you’re specifying, then there’s a very high risk that expectations will not be met and that the clients will be unhappy.
Da-Lite: When you can speak with the actual users, what do you say?
Park: Easy. "Show me." You want to take a close look at the kinds of overhead transparencies they’re producing, the kinds of slides they’re producing and, if they’re doing computer imaging, the kinds of graphical images they intend to show.
With the computer stuff you’ll get lots of variety, from the person who is used to doing her presentations with a pre-formatted, good guideline, no more than 7 lines of text on what I’ll call a slide but which may in fact be a direct computer- to-displayed image, to the guy who’s interested in showing C++ code which, on his 17-inch monitor, is displayed 50 or 60 lines deep. And the audience, which may be a group of ten people or a group of 100 people, all need to be able to read that.
Now, to a certain extent, you have to educate your clients to the laws of visual acuity. Unless we make that character two inches tall when we show it, once you get past 50 feet you’re not going to see it anyway. So, to make 50 lines of codes visible at that scale may require a screen size well beyond what the building will support.
You can see why you may have to compromise. But as long as everybody’s educated about what that compromise is (and everybody remembers it when the project is done), then everybody wins. But in most cases I think you can say that in conventional building design for rooms of the kind we’re talking about which, after all, generally seat about 25 people, that it’s very easy to get appropriate screen size and appropriate room volume around it so that the image is up at a place where people can see it.
Da-Lite: Do you mean see or, do you really mean read?
Park: Absolutely I mean read. Over the past five years everyone has learned to be guided much more by the issues of reading than of seeing. We will always argue that to design for the former will satisfy the latter. In my experience there are very, very few facilities being designed these days which do not have readable alpha-numerics as the key criterion.
Da-Lite: How about when the image content is purely graphical, when, for instance, it’s highly detailed CAD material?
Park: Well, here you start to push the issue of what a building can accommodate. In a conventional office building, it’s virtually impractical to put in a screen that’s more than six feet tall, given the norms of slab to slab construction. So when your client wants to display that high a level of resolution on an image large enough to take it, you have to rely on the computer’s ability to zoom up on at least a portion of the image so that its readable. The good news is computers will do that. And conventional optical media, slides or overheads, won’t. At least not on an ad hoc basis, when I need it, right now.
Da-Lite: Whre do you come out on the subject of front projection versus rear?
Park: My position is that in any facility where one of the imperatives is interaction between the participants, whether it be in a corporate boardroom, or a symposia-lecture setting, or if it’s in training or in sales or marketing, rear projection is the preferred methodology to display imagery. If the point, conversely, is to establish what I call a theatrical” presentation, a show, a staged event, front screen is normally and perfectly acceptable.
Da-Lite: When doing rear screens, how averse are you to using mirrors?
Park: Not nearly as much as I used to be. Of course, if you have the opportunity to design a building envelope, you want to avoid mirrors because they cost you brightness. But most of the time you don’t have that luxury and the extra 150 square feet of leased space is too expensive to your client not to warrant at least looking at a single mirror bounce to reduce that throw distance.
Da-Lite: When, for whatever reason, you’re obliged to use front screens and the application isn’t, as you put it, theatrical, what about the issue of lighting?
Park: I have been arguing recently that with advances in high gain front screen formulations (like your Silver Lenticular and the High Power material) that if you can do careful lighting control, that is, with as close to zero vertical foot candles incident to the screen’s front surface as can be managed with zoning, switching, dimming, scene selection, etc., you actually can get close to 30 usable horizontal foot candles on what I call the desktop or the audience laptop.
I will say the perceived image quality will be better if it’s a rear screen application, but the same rules apply. If you take a fully lighted room, turn off the lights in the front third and leave the back two thirds at half the original, fully lighted level (whatever that may have been), then, front or rear, you’ll get perfectly acceptable imagery.
Da-Lite: What about the question of audience size versus audience configuration?
Park: This goes back to the issue of visual acuity. I generally work with a ratio between image height to audience depth of 6:1. That goes against the current published 8:1 guideline, but when the clients are relying on computers to generate imagery which is likely to be something like a Windows® 95 full screen display, you need the bigger size.
Eight to one is still OK as long as you can say that you’re going to work within established standards of no more than 14 lines of text and preferably only seven lines of single-spaced text. But especially when the system includes what I’ll call video foils or a graphics cameras taking the traditional overhead transparency and converting it into a 3:4 video image, the 6:1 ratio gives me the ability to make that page of text big enough.
Da-Lite: If 6:1, then, tells us how best to size a screen relative to the back row, what can you say about the front row?
Park: That’s a tougher question, because it’s much more forgiving. If you want to provide a comfort zone for the presenter at the front of the house, using 2H will give him sufficient space to work the stage. However, there are many other facilities where 1H is perfectly acceptable. And by that, I mean that I can sit 1H back from the screen and read the data without having them be compromised. Thinking about it in terms of screen width, I’d say at least 1W and maybe more, maybe 1½ W. Two times W is extravagant..
Da-Lite: Are there any width limitations for an audience array?
Park: Yes. I don’t want anybody seated more than 60º off the transmitted (or reflected) angle by which I mean that I want no one positioned before the left side of the screen to be outside of a cone formed by the outermost light ray passing through the right side of the screen and line forming a 60º angle with that ray. In addition I think that ideally no row should be wider than 3W.
Da-Lite: Is another limiting factor of contemporary displays resolution?
Park: You bet. As we've seen video become the dominate display technology there has been a related convergence of traditional optical technologies into that same video field. And when you introduce clients , for example, to the various scanners, or to slide-to-video conversion devices, or to graphics cameras as replacements for overhead devices, they are sorely depressed when they see what 525 lines does to that old, zillion line slide that they had or that overhead transparency they spent so much time working on. Those once fine images now look pretty poor: soft, fuzzy, out-of-focus.
Of course the other side of the argument is that now that it’s in video I can do with it whatever I please in terms of where it goes or to how many people it goes and all the other potentialities which the medium enables.
Da-Lite: And what about screen gain? Do you have preferences?
Park: I am a practitioner and I base my recommendations and my designs as much on experience as on theory. Hence over time I have become convinced that a flatter gain surface, with a more even resolution across the visual field-of-view is better in all cases than a higher gain surface which sacrifices a wide field-of-view. Uniformity is more important than gain.
In my office we stay with the low gain screens: Matte White fronts and the 1 to 1½ gain rear screens are our bread and butter. However, there are cases where screen brightness beyond SMPTE standards (18 foot candles for video and 24 foot candles for slides) is required and when that happens I pitch, as strongly as I can, Fresnel-Lenticular screens because of their uniformity. Selecting and sizing the right screen is important. It is, after all, the one thing the client is sure to look at.