I combined two smartphone makro-lenses and took some pictures of my prints. What do you think? Do you prefer an fully closed toplayer or an absolute flat toplayer?
Edit: 0.4mm-100mm/s-10.000mm/s²-PETG
Very good @Stephanie_A is a great judge for these
I would say I’d depends on the part. Flat for appearance, fully closed for strength or moisture resistance.
I like it closed. See Eric’s comment for what that says about me.
Watertight.
If your using slic3r try setting the top infill 0.05mm smaller than your nozzle is 
for example 0.35 for a 0.4 nozzle
@VolksTrieb To reach what?
@Rene_Jurack to reach a smooth surface
@VolksTrieb the surface is as smooth as it can get. I’m talking about the ends and beginnings of the tracks of the topfill and their typical “blobiness”. After playing around with all the parameters that affect this, I figured that I can either have a very even and flat toplayer or a closed toplayer at these spots. Even orientating the topinfill to 90deg does the same, at least on 2 sides of the part.
@Rene_Jurack Jup but thats the point. This is the theory but it works: setting the top layer width lower than your nozzle lets room to fill out the gaps and NOT overfilling the ends of a line. Ill try to take a photo Well the thick ends of the line are the printhead slowing down, in the hotend the filament wants to expand and so it does, also at corners of perimeters. Cranking up your jerk and acceleration helps a lot but there is a limit to our “not-as-rigit-as-a-milling-machine-printers” and also to the motors. Printing slower helps and printing with more accerlation helps and also my advice of setting the line width
when setting a smaller nozzle size for the toplayer, I simply get an underextruded toplayer. This is trading the one for the other :-/
@Rene_Jurack no dont change the nozzle size change the top solid infill line width