When I draw in Krita, it shows a very light line until I either let go of the left mouse button or lift my pen off the tablet, in which case it then darkens the line.
Is this normal and if so, can this setting be changed?

Are you using the line drawing tool in a vector layer? If so, that is normal behaviour because krita shows a 'construction' line before drawing in the line with full properties after you finish dragging and positioning the construction line. I don't know of any way to change that behaviour.

If you draw a line in a paint layer then stop moving the end point for a short time, it will show a preview of what the completed line will look like.

I'm using the freehand brush tool. As long as I either the pen nub is still on the tablet or the left mouse held, it will not bring the line into full opacity.(even when paused and held) If I'm working zoomed out a bit at high resolution, it's a bit difficult to see my progress.

I've not seen or read about anything like that so I can't give any advice. Questions that other people may ask are as follows:

What OS and version of krita are you using?
Have you been using krita for long and has it always been like this?
Have you made any changes to settings, etc that might have caused this?
Can you provide (via Imgur or similar) a full .png screenshot of this happening?
Have you tried it with different brushes?

Hello, maybe you can try to desactivate "instant preview" in the "view" menu...

mcoudert wrote:Hello, maybe you can try to desactivate "instant preview" in the "view" menu...

That's exactly what it was! Much appreciated:)

That is curious, because that certainly shouldn't have the described effect.

boudewijn wrote:That is curious, because that certainly shouldn't have the described effect.

Using windows 10...I don't believe it did it with all the brushes. I don't think the gel pens and such did it. But the paint brushes and pencils certainly did. How is that feature supposed to work?

boudewijn wrote:That is curious, because that certainly shouldn't have the described effect.

@boudewin : i have noticed it before on windows (with old version like 2.9.x) but never report it because i have a recent PC and i always deasctivate instant preview mode...
By the way, in the latests versions i haven't noticed it (since 3.1 i think)

mcoudert wrote:

boudewijn wrote:That is curious, because that certainly shouldn't have the described effect.

@boudewin : i have noticed it before on windows (with old version like 2.9.x) but never report it because i have a recent PC and i always deasctivate instant preview mode...
By the way, in the latests versions i haven't noticed it (since 3.1 i think)

I've got version 3.3.1....but your suggestion appears to have resolved the issue.

WarBeer wrote:

mcoudert wrote:

boudewijn wrote:That is curious, because that certainly shouldn't have the described effect.

@boudewin : i have noticed it before on windows (with old version like 2.9.x) but never report it because i have a recent PC and i always deasctivate instant preview mode...
By the way, in the latests versions i haven't noticed it (since 3.1 i think)

I've got version 3.3.1....but your suggestion appears to have resolved the issue.

Maybe you can try the 4.1.1 with preview mode activated and tell us if the problem appears?

Maybe you can try the 4.1.1 with preview mode activated and tell us if the problem appears?[/quote]

Installed 4.1.1 and there's no issue with either setting:)