XX1 chain line on a 256 frame

[carbonazza]

I'm on chain worries today...

I don't know the theory behind the chain line.
And what is a good or bad chain line.
And if this plays a role in chain wear.

But it looks odd to me that the chain is straightest when on the 3rd smaller sprocket.
See the picture.

I was expecting the chain to be straight when sitting in the middle of the cassette.
Do you have the same angles?

[Pedalphil]

Have you got a steel rule to run across the larger cogs to use as a gauge to check the angles, as its hard to tell from the photo.

[carbonazza]

I don't have a steel rule or similar. I'll try to find one. Thanks.