I am TERAI, a guest researcher.
At the event for new technology introduction at the restaurant on March 27, I will create equipment for customers to call a waiter using Kinect by Microsoft. In this project we will use projectors, so I researched projectors for the installation.
The latest projectors support various new features such as 3D supported and high vision picture quality. In order to use them for the installation, I think people only have to pay attention is to check the following summarized points.
There are two kinds of projectors characteristically different which I have now; an MW824ST which is a new model by BenQ and an EH-EH-TW400 which is an old model released about 2 years ago by EPSON. So, I want to check which projectors will fit to use by projecting images on screens in real time.
Note: An EPSON EH-TW400 is shown in the left of the photo and a BenQ MW824ST is shown in the right
Near focus (binocular vision)
It’s not “simple”, but “near” focus. For example, when people want to project a hundred inch image, it matters how far projectors should be placed to be able to see the image. The projector which needs to be placed at 2 meters is more “near focus” than the model at 4 meters, and near focus model is more convenient for a Kinect installation in an inside of a restaurant where spaces are limited.
The picture on the left is an MW824ST projector with more near focus. Both projectors are placed at a distance of 1 m from a wall, but due to the angle of field differences, the display size is different by this much. For example, when people want to project images at a ceiling, since the height to a ceiling is generally 2.5 meters, the nearer the focus is, the bigger images people can project at a ceiling.
*As TW400 is not a near focus projector, people can see the picture plane much brighter in comparison.
Max brightness (lumen)
The darker an event site is, the more beautiful images a projectors to be used in the installation can project. On the other hand, since the event site is a restaurant this time, its main purpose is dishes no doubt. The fluorescent light fittings are assembled to make the dishes delicious, so we cannot make the site completely dark without careful consideration. So, it is important to consider both “picture plane” and “projection instrument (projector)” so that people can see projected images even at brighter site.
As a result of getting a preview of the restaurant, for a proposed projection spot for the Kinect installation, I thought I would choose one from wall surface glass, wall surfaces, ceilings, tables, objects, and projection mapping to objects. I thought projection to wall surface glasses was the best choice in order to surprise guests, and I tossed around the idea if images loomed out on the glass by attaching netted doors (amid screens) and agricultural polyvinyl (polid screens) to glass; however, as the result of consideration, the idea of projection to glass was deferred by considering the site brightness. I will introduce this verification in another entry. For an actual status, projecting images to ceilings is a possible choice.
Projection instrument (projector)
When people want to project images at a bright site, the brighter brightness is, the clearer people can see images. Besides brightness, contrast ratio is also a benchmark to choose projectors, but when I asked a shop stuff at a home appliance retailer, he told me that contrast ratio is not a reliable factor to that extent. I found some comments about that on the internet. I got a MW824ST projector with 3200 lumen and a TW400 bright projector with 2600 lumen.
Trapezoidal shape change and mirrored image inversion
In case of site layout, a place to put projectors on is also a point to check. It is not so usual to be able to project images in front of picture plane. The latest projectors have an up and down angle adjustment feature and right and left shape change feature depending on the models.
Caution: Even TW400 which does not have near focus feature can project images to a large screen within a certain distance, and only this model has a right and left shape adjustment feature, so a projector can be projected obliquely by itself.
In addition, with a rear projection feature, by using amid screen and polid screen as I told before, when images are projected from the rear, as a rear pro is, in other word, a mirror-reversed display, it is useful when images are projected with inverting projector’s images to a mirror.
Projecting inverted images to a ceiling by setting a mirror in front of TW400. Because mirror images are inverted when reflected to a mirror, by using a rear pro feature on the projector, the images are displayed accurately. Because the other projector MW824ST has a near focus and wide field of view, the images projected are easy to project off the mirror unless the mirror is big enough.
openFrameworks Tips：This time I will create an application for installation at openFrameworks.
OpenFrameworks has an add-on called “ofxQuadWarp”, and by moving each corner of images to display, it perfectly fits intto a targeted object by changing shapes and inverting images.
I did not take consideration this time but here is another following method for installation projectors.
Projecting images with several projectors
There is a method to project images to the same surface with several projectors all of which air the same pictures, which is often used outside installation where vast amounts of brightness are needed. Although PCs which air pictures become overloaded with making tracings and there is a risk in proportion to the units of projectors as noises and amount of heat generation are bigger, because brightness can be doubled, the method is often used in installation events with big budgets and scales.
I tested two new and old projectors this time but I thought that the one is not always almighty and each one has a natural inclination to be used to fit depending on the environment of installation sites. By allowing for these projector’s characteristics written here, it will be important to look at the event site beforehand.