Observations on NikonScanís Color Negative Film Setting
Previous versions of NikonScan functioned the same as transparency scanning except that it also inverted the image. NikonScan's color negative mode is different in that it also performs substantial post-scan processing and thus has essentially become a black-box operation.
To understand the requirements of scanning color
negatives and context of this note see Scanning
NikonScan 3/4 seems to perform these steps:
If you don't want to use NikonScan's method, I would recommend scanning negatives as positives and using inversion curves. When you consider the time otherwise spent in correction, this method requires less time. I've put up a page outlining several methods to do this: Inverting Negatives to Positives
The Problem with NikonScan's Negative Scan Mode
This is a typical histogram after executing autoexposure on a Kodacolor image with a full range of tones:
A significant part of the tonal range is unavailable and the ability to separate tones is impaired. Trying to analog gain to adjust the image only aggravates the problem. To show that this is a hard limit, the analog gain was set to -0.5. Instead of shifting the distribution left, into values below 30, NikonScan crams more detail against the lower limit, like a wave hitting a brick wall:
The values that were clipped in fig.1 have been moved into the range of imaged values, but pushes some of the shadow tones into the left margin.
Itís clear that the controversial effects of the negative scan mode arise during post-processing and not as a result of setting exposure as I had thought earlier.
NikonScanís negative scan mode makes sense when looked at in the context of a batch processing operation. The method automatically sets the black-white points and achieves a reasonably long tonal range, a real time-saver for the volume user. Why did they choose 30 (this will vary depending on the user's screen gamma selection) as the bottom end? Probably because most printers don't begin to show tonal differentiation until about 30, everything below is black.