60 frames per second: What this means to you and your visitors.

We all know that a visitor’s experience is one of the most important things to our planetariums and these days, with fulldome theaters, we can now present them with even more impressive shows to enjoy. However, there are still ways that we can improve upon the process and deliver an even greater visitor experience.

One of the improvements that we’ve been working on here at the Clark Planetarium is to shift our productions from the current 30 frames per second (or “fps”) standard to a new 60 fps standard. And we’re not alone. Right now, the film industry is also experimenting with faster frame rates to increase the quality of their films and enhance the viewing experience. Full dome institutions can also benefit from this improvement in pronounced ways.

Let's outline the key elements of a 60 fps full-dome production and what it can bring to your audiences.

The FPS Shift

At 30 fps, we are seeing 30 discreet frames per second projected onto our domes. When we increase the frame rate to 60, not only are we doubling the frames being shown per second, but we are also doubling the amount of perceived detail a scene actually contains.

Frame Rate vs Refresh Rate

To understand how this works, we need to look at how frame rates compare to refresh rates. The frame rate refers to how many discrete, or individual images, are projected on the screen each second. The refresh rate is the number of times a second the display hardware (a monitor or projector) draws the image. This rate is measured in Hz. So, for example, when you play back 30 fps content on a 120 Hz projector, the display hardware is projecting four frames of information for every frame of content. To achieve this, it has to repeat each frame four times (4x30=120).

At 60 fps, on the other hand, the projector is only duplicating frames twice a second, thereby doubling the information presented each second.

In our tests at the Clark Planetarium, we've noticed that there are tradeoffs to increasing the frame rate. While there are certainly benefits to increasing it from a quality perspective, there are also increased costs associated with it as well.

Benefits of 60 fps Content

  • Smoother Playback
  • Increased Visual Quality
  • Clearer Colors (less muted)
  • Increased Sense of Motion

Smoother Motion and Depth

When comparing 30 fps to 60 fps, in the latter, objects traveling across the dome are smoother, crisper, and have a greater feeling of depth. For example, stars in a star field no longer jitter while moving across the dome. To fully appreciate this, however, you have to experience it for yourself. We have a 60 fps full-dome demo available to you for free, and we also have a few demos for you to check out online: Compare Frames Per Second

Perceived Increased Detail

As we mentioned before, content played back at 60 fps has double the amount of perceived visual information displayed as content played back at 30 fps. Content rendered out at 60 fps also adds motion that is absent in content displayed at 30 fps. This equates to literally twice the amount of information being displayed.

Increased Sense of Motion

With double the amount of information being displayed, the viewer is much more sensitive to motion on the dome. Moving through even simple environments is much more immersive, and the increased smoothness of the motion playback draws audiences even further into the show. For those of us who have been working in the fulldome field for a long time, it actually brings back the sense of wonder in feeling motion that we have lost over the years through repeated exposure.

Not only is the planetarium industry shifting to a faster “frames per second” standard, the film industry itself is also moving in that direction.

"Film purists will criticize the lack of blur and strobing artifacts, but all of our crew - many of whom are film purists - are now converts. You get used to this "new look" very quickly and it becomes a much more life-like and comfortable viewing experience... There's no doubt that we're heading towards movies being shot and projected at higher frame rates." - Peter Jackson switching to 48 fps
James Cameron Demos the Future of Cinema at 60 FPS.

Cost/Benefit Comparison of 60 fps vs. 8k

Of course there is extra cost associated with a 60 fps production. The jump from 30 fps to 60 fps doubles the render time, and similarly increases the required storage capacity for the frames. Both are expenses that need to be taken into consideration for your production.

Typical planetarium productions are currently rendered at a resolution of 4k (or 4096 pixels by 4096 pixels per frame). We’ve done tests where we have quadrupled the frame resolution to 8k while leaving the frame rate at 30 fps. How did this compare to 4k images being displayed at 60 fps? Based on our experience, public observers didn’t notice a big difference in image detail when going from 4k to 8k. But they *did* notice, even at the lower resolution, that content at 60 fps had less frame jitter and motion blurring for objects moving at even a moderate pace across the dome.

When you consider that it takes eight times the amount of time to produce true 8k detail over 4k (because the area calculation goes up exponentially) and compare that to taking only twice the amount of time to double the frame rate at 4k, the cost/benefits winner becomes clear. Not only that, there are savings on storage space, render times, and compositing times. Audiences will notice improvements far more readily with a faster frame rate than they will with greater image resolution.

Here at the Clark Planetarium, we're getting a lot of positive feedback from our audiences. They greatly prefer the smoother motion and depth, perceived increased detail, and heightened sense of motion. In their words, they say over and over that the scenes "feel more real" and "less like a movie."

As Mr. Jackson mentions above, this is the future.

Test Our Demo On Your System!

We have developed a 3-minute demo of 60 fps content for anyone who wants to try it on their system (provided your hardware and encoding can support the higher frame rate). Send us a hard drive and we can supply you with the master frames (118 Gb PNG files). We already have an encode available for Digistar systems. Mail your drive to Mike Murray, Clark Planetarium, 110 South 400 West, Salt Lake City, UT, 84101 USA.