While Microsoft"s HoloLens is a fantastical innovation blending your reality with a digital facsimile; one thing it does not do very well is allow you to share this experience with others. Spectator view is a Microsoft-sanctioned hack that combines a bunch of hardware with some clever software tricks in allowing others to look in on your augmented world, in real time and in high quality.
HoloLens already offers a similar functionality via a feature called Mixed Reality Capture (MRC). However, MRC has several constraints due to being built into the device, thus offering a lower quality of capture and other problems associated with capturing input from the first-person view, for example including the user"s head movements, which may be confusing to a viewer.
In simpler terms, MRC offers a first-person perspective of the augmented reality experience, while spectator view uses a DSLR in conjunction with software to provide a third person view of the augmented construction, and at a higher quality. In essence, this is similar to the manner in which Microsoft allows audience members to look in on their reps using a HoloLens at events, though at a fraction of the cost of the setup used.
Not an official product sold by Microsoft, spectator view is more of a DIY hack for those who are familiar with programming and able to follow Microsoft"s rather detailed instructions on GitHub on how to set up your own rig and the accompanying video guide (included above). Alongside the competence to follow them, you will also need a DSLR and a second HoloLens device.
With all of that setup, the DSLR will basically record its surroundings with the inclusion of any holograms you have set up in the space, presenting the ability to both stream live and record video, alongside taking still pictures.
source: Microsoft via MSPoweruser