Higher Efficiency with Truncated Projection
Single projector systems are much more efficient when using truncated projection. The image below illustrates why. Fulldome projection (orange) is limited to the vertical resolution of the panel, while truncated projection (blue) uses the full horizontal resolution. For a typical 16×10 aspect ratio, this translates to 67% higher resolution and brightness in the image.
What resolution do I need?
While important, resolution alone does not guarantee good image quality. Color saturation, contrast, and frame rate are equally and sometimes even more important than raw pixel count.
Color Saturation: Laser and LED light engines have improved the color saturation of single chip DLP projectors so that they now rival 3-chip projectors. All OmniFocus systems offer excellent color saturation.
Contrast: All projection systems project some light, even for black. This is known as “video black”. Typically, this is only important for blended multi-projector solutions and dark images (i.e. stars in the night sky). When the image is bright, the contrast is limited by cross-illumination from one side of the screen to the other. Elumenati’s LED products offer great LED color saturation while eliminating video black and cross illumination for fantastic image contrast.
Resolution and Frame Rate: Can HD be higher resolution than 4K? The answer is yes. If an HD display is run at 120 Hz frame rate and the 4K at only 60 Hz, the lower resolution display will offer better resolution for any object moving faster than 2.5°/sec. For perspective, that object would need 72 seconds to sweep across the 180° of a GeoDome Portal!
Experience Design with Truncated Screen Shapes
As a rule of thumb, fulldome projection is optimized for concentric seating, while truncated projection is optimized for theatrical seating where all the audience is facing forward.
Fulldome projection into a 180° hemisphere puts all the image above the audience. While this is great for night sky astronomy, it forces the subject matter to be at the top center of the dome which is not ideal for many immersive experiences – especially feet-on-the-ground stories like walking through the pyramids of Egypt, understanding geological features, or walking through 360° spaces in client design reviews.
Truncated screen shapes allow us to use theatrical seating with the audience all facing forward, and further allows us to extend the screen below the audience horizon. This greatly enhances the storytelling capabilities. With the exception of the Evolver, all GeoDome screens extend below the horizon, vastly improving the audience’s sense of presence.
Many modern dome theaters use theatrical seating combined with a tilted fulldome to compensate for the limitations of fulldome projection. This provides some image below the audience (in front). On the other hand, the image quickly moves above their horizon and the rear 25% of the screen is rarely even seen at all! Rather than trying to force fulldome projection to work with theatrical seating, we recommend considering truncated instead.