4K Confusion

2023-11-08 / Rob Spearman / Buyer Guide

A Digitalis competitor recently announced a new portable digital planetarium system. See what you think of the announced specifications:

1. 4k resolution: 3840x2160, over 8 million pixels
2. Single lens with no rainbows at the horizon like competing systems
3. Fulldome projection with 190 degree projection angle with 36” springline (unlike 155 degree competing models)
4. No need to learn Linux like some competing models
5. Metal frame, unlike the plastic competition

Sounds great, right? Well, at least to those unfamiliar with digital planetarium market. Let us go item by item and pull these claims apart:

1. While the projector chip is 4k, and indeed has over 8 million pixels, the planetarium system is not 4k! It is actually 2k per industry standards. This is because a single fisheye lens projects only a fraction of the projector pixels onto the dome. Fisheye projection resolution is measured across the diameter of the dome. Here the resolution is precisely 2160 pixels, the same effective resolution as our Digitarium Theta 2 system, for example. So this is extremely misleading. In fact, only 3.66 million pixels make it onto the dome, less than half the pixels in the projector! See the illustration below.



2. We are not aware of any commercially available single-lens planetarium systems with rainbow horizons.
3. To begin with, there are no 155 degree planetarium systems on the market. Secondly, while it may sound impressive, a 190 degree projection means that the lens has to be higher than the projected horizon. That means it will block some sight lines for audience members and/or uncomfortably project into their eyes. It also means the horizon height is not a static number, but will vary with your dome size. See the illustration below. Our Digitarium Theta 2 system has a 175 degree projection angle.



4. No commercially available portable digital planetarium we are aware of has ever required the operator to learn the Linux operating system. (All Digitarium systems run this very stable and secure embedded operating system, but it is completely hidden from the user.)
5. All the commercially available single-lens portable digital planetarium systems we have ever seen use metal frames or enclosures.

Why would a company make such false or misleading claims? I will have to leave that as an exercise for the reader.

If, instead, you want to talk to expert planetarians you can trust in order to discuss your needs or questions, please get in touch.