It lets you increase or decrease image contrast by using two points-
one at the three-quarters point on the curve, one at the one quarter
point.
how much it will increse or decrese the contrast? Â in other words, you
only say where to put the control point, but dont say where are they
new position.
I really suggest playing with it manually by setting the histogram to
cuves.
It gives you control over how steep the curve is in the midtones, but
you're stuck with the two control points it gives you and can't move
them left or right, only up or down. Photoshop is a lot more
flexible, so I don't use this feature.
I believe Vuescan applies curves to the raw data so there may be some
theoretical quality advantage to this approach (but that is then wiped
out by the lack of control over the curves and you then distort it
again in Photoshop to fix it).
and, i am thinking another question: can i get the raw tiff file
compatiable with Photoshop? i guess i can turn off any post control,
including color blance, b/w points, curve modification and grain
reducaton, then the output tiff should be raw. am i right?
You don't want a truly "raw" tiff based on your above posts.
Just set color balance to none, use the advanced workflow and the
resulting 16 bit tiff will of course open in Photoshop.
points setting and film type seledtion, do these still have effect on
output image? if so, i think the output image is still not 'raw'. am
i right?
Keep film type as generic color negative. The black/white points are
not settable when color balance is set to none. If you don't fiddle
with all the settings you will get a less altered scan.
Roger