I haven’t written a technical piece in a while, but I’ve been moderating AVIXA ‘s Control Room Power Hour series of webinars, and a subject that has come up a lot is the use of projection in data visualization environments.
Projectors are still viable in these types of rooms. With the advent of laser projection, issues due to colorshift, dimming of bulbs and long-term projector maintenance have been minimized dramatically, assuring that the Day 365 experience will be very similar to the Day 1 experience with these systems.
Given the sensitivity of data, its importance to decision making and the fine detail that sometimes exists in the content in these systems, there are still some pitfalls to avoid when choosing projection over an LCD video wall or direct view LED technologies. With that, I thought I’d share some common scenarios to avoid to assure your projection system works in the best way possible.
1) Utilize the Native Resolution of the Projector
In many single-chip DLP projectors, the projectors can produce a 4K image, but they do this by moving a 2560×1600 chip to fill different portions of the screen. When watching pictures or moving video, this is not typically an issue, but when you blow up an image to a large scale and show text and data, the movement can become apparent and create fuzzy edges. If you buy one of these units, my advice is to turn off the 4K/UHD mode and utilize the native 2560×1600 resolution. The chip will stay still, and although you have less resolution, you’ll get a sharper image.
If you DO need 4K or UHD resolution, you should go to a projector with the larger DLP chip and native 4K DMD. Or, go to an LCD or SXRD projector with native 4K.
2) Avoid Blending and Stacking
Edge blending is an awesome technology and can be great for multiple projector implementations of art and entertainment, especially when combined with projection mapping in immersive environments. Stacking projectors to get more brightness can also work to help increase brightness and contrast in these environments.
However, in data visualizations, edge blending can be problematic. There may be banding based on overlapping black levels that affect grayscale images, and blend zones may not be as clear and precise when content goes across those zones. If you’re using multiple projectors in data visualization, it may be better to edge match them instead. If you need more brightness, it may be better to purchase a higher lumen projector as opposed to stacking two smaller projectors to increase brightness.
Even if you’re blending and overlaps are dead to rights on day 1, the mechanical alignment can shift over time, and maintenance and recalibration will be needed.
If you do need to blend, avoid stretching detailed content across the blend. Invest in a video processor that allows you to put content wherever you want to avoid the image’s degradation. If you need to stack, some projectors can map pixels to the same physical location with an onboard camera system to digitally maintain pixel alignment even when mechanical alignment shifts slightly.
3) Know Your Screen Materials
There are a lot of screen materials on the market. Front projection materials have added many Ambient Light Rejection (ALR) options, and rear projection may still be designed into some projects as well.
ALR screens have very specific cones. Rejecting ambient light typically means narrowing both the entry angle of the projected light as well as the viewable cone and the half gain angles of the screen. This means the screen may not be as bright for viewers on the edges, or certain short-throw lens options may not work well. Many ALR screens also have reduced horizontal viewing angles that don’t allow for the edge blending mentioned above. Know the tradeoffs that you may make when choosing one of these materials to increase contrast.
As for rear projection, make sure that you plan the entry angle of light from the projector appropriately here as well. With some of the short throw lenses that place the lens above or below the screen, the light from the projector enters the rear projection material at too steep an angle, creating refraction inside the material or ghosting. If you are planning on rear projection, mirror systems typically produce the best results when compared to using short throw lenses that “spread” the light out faster.
If you’re looking to take a visualization room to the next level, and want to create a group VR/AR experience, check out High Frame Rate (HFR) projection. HFR projection can create three separate images on the screen for three unique viewers. With the appropriate glasses, each viewer can move around the room to get a unique and different 3D perspective of the screen, as a computer alternates frames for each viewer and the glasses sort through which images are meant for each person.
It’s like VR without a headset, and the three people can all see and talk to each other as they explore a virtual object from different perspectives. It’s really, really cool.