Recently I bought a second guitar, before I had for almost 8 years just one guitar and did not noticed that its action was quite high. When I took the guitars of others I often wondered that they where much more comfortable to play, but I thought it was an issue of the guitar itself and I had no idea how to adjust this. As I got my 2nd guitar I noticed the same, and also noticed that the saddle was much lower.
So I did some research and found out that replacing (or sanding) the saddle can help lowering the action, so I did this with my first guitar getting the action from 6mm down to ~4mm, see the picture:
But I am trying to get it even lower, but the saddle is already quite low. So I did some further research and found out that this could be achieved by adjusting the truss rod.
But before doing this, I would like to know. What bending of the neck is considered normal? I could not find any comparing pictures on the internet, so I am asking. My other guitar has also a slight bend, so I guess some curve in the neck might be normal, but I wonder what degree might be normal (so that I do not adjust my guitar wrongly)?
So what bending is normal? Or should I aim for as flat as possible?
As written here:
Ideally we are adjusting the truss rod to render the neck as flat as possible without creating too much string buzz.
and they also write the optimal action is between .004-.006in (~0.127mm, see this sheet), so their might be plenty of room to adjust my action of 4mm.