Stefan Krohmer wrote:
Hi Stefan,

I'm using 8.4.57, but I think this is the same.

This procedure is rather indirect and not obvious, but not difficult.
It's part of what the manual calls 'Advanced Workflow', which involves
reading the film base color by scanning a piece of the film leader, but
if you're happy with the color you already have, it's not necessary to
do this operation.

What you want to do is go to the Input tab and near the bottom, check
the box for Lock exposure. This will make visible another checkbox,
further down called Lock film base color. Checking this one too will
make yet another one visible below, called Lock image color. Checking
that one will get you the effect you seek. You should now be able to
recrop however you wish, without triggering the automatic algorithms to
recalculate. Do these steps after you have made any color adjustments
you want in the Color tab, such as refining bp, wp, curve lo, hi,
various brightnesses, etc. In other words, just before your step 3. above.

Hope this is what you were looking for.

Best regards,
Mike