target appear lighter than your current layer, move the midpoint up to
lighten the layer and better match your target. Use small increments, and
continuously use your eyes to evaluate the changes.
If things don’t look quite right still, locate the lightest shade of grey (but
not white, as this could be a specular highlight — not something you want
to factor in much, with compositing) on the target image, and do the same
with figure 2. With your eyes darting between these two greyscale shades,
move the white slider on the Curves dialog box until the shades visually
match. Next, do exactly the same process with the darkest part of the
image, moving the black slider in the Curves dialog.
Curves adjustments for the red channel