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filmscanners: Re: nikonscan white clipping



Mike Duncan schrieb:
 
> To extend highlight detail in negatives with NikonScan, use curves.  Leave
> the 255 point alone.  You need to bend the curve downward a little at 230
> input to approx. 215 output and optionally raise 128 input near to the
> straight line level (~114).  With a gray scale color negative this greatly
> enhances highlight detail.  When you get the curve you like, save it.

Hi, Mike,

sorry for contradicting, but if you do it this way, you are in danger of
clipping the highlights first and then just darkening them - this will
seem as more highlight detail but IMHO just turn white into light grey.

Here is how I proceed:

With every single negative, use analog gain until you get a histogram
that, for each of the R/G/B channels, has its "slope" end just before it
"touches" the right side of the scale. Use the auto adjust for the white
and black point *for each channel separately* - this is important
because the RGB histogram just displays sort of an "average" view of the
three color channels. Then - this is important again - push the "white
point" slider of *each color channel* just a tiny little bit to the
right to be absolutely certain no highlights will burn out (the preview
usually "misses" some of the brighter points, i. e. the histogram of the
complete scan will most likely extend a bit more into the highlights and
shadows area than the preview did. By moving the slider you get some
extra "space" for those missed highlights).

Mike, pushing the curve downward like you do, simply speaking, just
transforms an array of 255/255/255 pixels into one of 230/230/230
pixels. The way I proceed will prevent the 255/255/255 pixels from
occurring at all (YMMV).

BTW, you will in many cases be unable to do the same at the "shadow"
side of the histogram because Nikon Scan has a weird aspect of the
histogram - it often looks asymmetric, somewhat like a logarithmic
display. Don't worry, just let the black point automatics do that for
you - as opposed to the white point automatics, the black point is
selected in a "conservative" way, almost never producing clipped shadow
areas.

See ya -

Ralf

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