Comment 3 for bug 1649122

> Perhaps this adaptation mechanism at the border ceases
> to work when the exposure is too far off. There might
> even be a built-in limit to prevent side-effects like
> increased noise.

Neither is there an `adaptation mechanism' nor a `built-in limit'.
What you see is just the Mertens/Kautz/van Reeth algorithm at
work. If you dig deeper in this issue database you may even
find a bug report where Enblend did not exactly reproduce the
parts of the images that were not overlapping.

Please review change
    http://hg.code.sf.net/p/enblend/code/rev/04948f29c8ed
where I added some clarifying paragraphs to the documentation.