Why is my Space so Noisy?
What happens when scanning a site with low light? Unfortunately, what the camera sees is not exactly what our eyes see and when you try to introduce ambiance by dimming the lights, or just using the available light at a low lit restaurant/coffee shop, image noise will happen.
All cameras have three settings they can adjust to change the exposure of the recorded image - Shutter Speed, Aperture, and ISO. Because Matterport is fully automated, it's preprogrammed to optimize these three settings to get you the best result possible - for it's purpose. Meaning, if you are in a low lit restaurant and want to give your Space that romantic atmosphere feeling, unfortunately, the camera doesn't know that and will do everything it can to crank up the brightness to get you a well balanced exposure.
In order to get that well balanced exposure or brighter image, in this case, the camera can't increase the aperture size since it's setup to focus on everything from near to far, which requires a small aperture. It can't slow down the shutter speed too much either since that will start taking way too long to scan each position. This leaves only one option, increasing the ISO.
The ISO is like the volume control on your stereo. If you turn up the volume, you'll hear the music louder, but you'll also hear the static and noise louder too. Images are the same and when you increase the ISO to brighten the image, you see the image noise stand way out.
But the question is how do you know when there isn't enough light for a good quality image. This is impossible to answer since everyone's threshold for quality and what is acceptable differs. For that reason, I've linked below 10 Spaces I did as a test to see what the image quality will be at different light settings. I used a Lux light meter, more about that below, and started scanning at 200 Lux working my way down to 5 Lux - which is very dim light. Keep in mind there was no light coming in from outside, so in most common cases, having that window light would increase the overall amount of light quite a bit. Having more light, to an extent, allows for even better noise management.
Checkout the linked Spaces to find your minimum Lux setting. Get yourself a Lux meter and know the results before you scan in low light.
Keep in mind as the light dims, the camera is trying harder to increase the brightness. This not only increases the noise in the shadows, but also makes the bright spots in the room overexposed.
Can anything be done to improved image noise after processing the Space? Unfortunately no. The pano images captured cannot be edited or filtered in any way at this time.
The Lux meter I used was the LX1330B selling for $40 on Amazon and you can see it in each of the test Spaces. There are also meters available from $16.