The discussion linked to below suggests setting the RGB to grayscale on the 400 Series using the Y16 format.
Regarding scaling down, you could use post-processing with a Decimation Filter.
SDK 2.0 has a post-processing sample program.
Thank you for your quick reply MartyG!
I looked into the links you sent me, but to be honest, I do not know how I would have to do that in my ROS setup.
I saw that the decimation filter in combination with the ROS wrapper is an open issue on Github. See: No available methods to filter depth stream · Issue #313 · intel-ros/realsense · GitHub
Also. ideally I would like to have not a grayscale pointcloud, but one without any color at all. But also grayscale would be better than rgb. However, the link you sent me also discussed this issue using the API, whereas I'm lookin for a solution using the ROS wrapper.
Do you have any suggestions?
I was not able to find support for decimation filtering yet in ROS.
In regard to your other question about removing color in ROS ... a question was posted, with an accompanying script, where the problem was that they had a white point cloud. So their problem could end up being your solution if you make use of their "wrong" script.
Edit: apparently the white point cloud was due to something in Rviz rather than produced by the script. So that is not likely to be the solution. My apologies. I will keep looking,
Edit 2: one approach is to disable the color image in the launch file, as discussed here: