How does this old Panasonic camcorder compare today?

The HDC-TM900 and its predecessor, the TM750, often sold with a lens adapter that allowed users to shoot 3D video. The limitations were:

1. The small apertures required lots of light,
2. No zoom, fixed focus.
3. The 3D effect was perceptible only for subjects around 10-15' distant.
4. 3D video could be edited only with software that supported 3D.
5. To view the video required a 3D display and special glasses
6. It is difficult to blend 2D and 3D video, other than by "stretching" the L or R frame of the 3D portion, resulting in reduced resolution.

3D content remains scarce, and the general public never became very enthusiastic about it. The industry then shifted to 4k and maybe eventually to 8k. Amateur video capture, meanwhile, shifted largely to phones. The versatility and connectivity of phones is hard to beat. The basic question is whether video viewed by a phone looks appreciably better if shot with something expensive and new, versus something old. The honest answer is probably "not much." By far the more important variables are content, editing, lighting, and audio.

The contrast-detect auto-focus struggles in low light or at long zoom. That remains true of just about all Panasonic imaging products. But the TM900 does allow for manual focus via a ring at the front of the camera, which can also be used to control iris / aperture , shutter speed, or video gain manually. The EVF is not particularly good, but the flip out touch-screen can rotate 180 degrees and is quite adaptable.

In some cases, used TM900s sell for under $300. It has both a mic and headphone jack. Its fan prevents over-heating, although its low humm sound can be heard faintly in video shot in a quiet setting, unless one turns down the gain manually. In good light, the video quality is acceptable for most uses. If has 5-channel audio, something no 4k device seems to offer. Time-lapse and low-lux modes are available. The 2-axis stabilization is helpful, but the small size of the camera will make hand-held shots a bit wobbly, particularly in long zoom. For long shots, a monopod is helpful. The AVCHD codec is not suited for color grading, but most people don't engage in that anyway.

Concerning 4k, what I've noticed is that lots of people with 4k displays don't really see 4k resolution. One reason is that, if a display is set to true 4 resolution, the size of text is too small to read, so they zoom the settings to 150%. Another reason is that one must be very close to a screen for eyes to see "real" 4k. Then there is the fact that our acute focal vision covers only a small portion of our fields of view. With some people obsessed with narrow depth of field, a lot of the frame may be blurry by design. Finally, how can anyone's eyes, with or without presbyopia, discern 4k on a phone screen?