Exposure problems and foremost color balance handling: yes,
this are the problems which I also experience with NikonScan.
Vuescan is of great help here.
Scan of negatives with NikonScan is also very troubled.
Especially, I notice from the histograms that NikonScan
never maps darkest gray to 0. All histograms seem to
indicate an offset of approx. 25%!
It does if you tell it to, Thomas.
However the default setting results in a black level which depends on
the density of the film base - that is what defines the black point on a
negative. The autoexposure will adjust this to ensure that the CCD
level is matched but not saturated in any of the colour channels and,
once inverted, the saturation level becomes peak black. Consequently
the film base level is therefore offset from this level by an amount
dependent on the density of the film base itself - which varies from
film type to type. I have never seen this get above 10 percent
(histogram black level=25).
There are two simple solutions to this.
First, set a global adjustment to the exposure that brings the black
level to 0 for the film type you use and then save that as the default
user setting or a specific film type setting. This approach has the
disadvantage that the film base can be a slightly different density
depending on the processing used, even on the same film type.
Consequently you might find that some blacks are actually clipped and
you need to rescan at preview level to get acceptable results. The
advantage of this technique is that you get a few percent extra in
dynamic range due to increased exposure and better use of the full CCD
dynamic range. Since negatives don't actually have anything like the
density range that the scanner can cope with, what actually matters is
the improved signal to noise ratio, which is dominated by shot noise on
the illumination itself. In practice the difference is almost
negligible - a 10% increase in exposure improves the SNR by around 3%,
so hardly a big deal. Even at your extreme 25% level, this is only
going to improve things by 5%, which is pretty negligible.
Second approach is just to define a black level on the curves window and
save that as a user default or film type setting. The advantages and
disadvantages of this approach are pretty much complementary to the
first solution.
Given the marginal disadvantage of operating the CCD close to
saturation, I prefer the latter, since I can make minor adjustments to
the black point without getting another preview on the rare occasions
that I just throw film at the scanner without checking which type it is
and choosing a setting I have previously created.
I haven't had NikonScan transfer an image into Photoshop which did not
have a good black level, (or histogram distribution for that matter)
since the day I bought the LS-4000 and started using it.
As for your problems on colour balance - once you get a default setting
that gives good blacks, find or create a test negative with good whites
and grey content - a colour chart is a good start. Then use the eye
droppers in the curves window to determine the white point from the
white areas of the image - you might need to make a few adjustments to
the final levels to give you a safe margin, depending on your preference
settings. Then use the gamma dropper to determine slope correction in
each colour channel from any of the grey sections. Store these with
your defaults for that film as well. Perfect colour balance (or at
least matching the colour of the light the image was shot under) every
time thereafter.
