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Color correct scans of negative film material using Vuescan

The following is based on Vuescan Version 7.6.46
Vuescan - in contrast to many other scanner software products - offers the opportunity to improve scan results by switching to the manual mode as well as setting and fixing the main parameters like film base color and white balance. Ed Hamrick, the author of Vuescan, describes the process as "advanced workflow suggestions".
Precondition for the following is that main settings are done already: scanner type, scanner resolution, file destination, file name, file format etc.

1. Set color balance to "manual":
   You can find this option on the "Color" tab.
   
   
   This is how a scan would look like using manual default settings for color neg. film
   
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2. Setting the correct film type:
   This is done on the tab "Color" by using the three options "Negative Vendor", "Negative Brand" (trade name); and "Negative Type" (emulsion, production lot etc.). Depending on the exact type negative films show - in contrast to slide films - very different behaviour which schould be considered in the lab when prints are made.
   
   
   The same scan after switching to correct film type
   
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3. Prescan a piece of unexposed film.
   A piece of film from the start or end of a role can be used as well as the unexposed area between two frames. Then crop to this piece of unexposed film.
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4. Set exposure value:
   Set the "lock exposure" option on the tab "Input". This adjusts the sanner light source to the strongest possible value without overexposing the CCD sensors in the most transparent areas of the film.
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5. Set film base color (mask color):
   Do another prescan and select the option "lock film base color" on the "Input" tab. The three values "Film Base Color Red", "Film Base Color Green" and "Film Base Color Blue" will appear in the "Color" tab.
   
   
   After determining the film base color
   
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6. Setting gray/white balance:
   You have to find a frame on the role of film with an area in a neutral grey color (ideally this would be a grey chart photographed with sunlight or flash illumination (for correct color temperature of the light)) and right-click this area with the mouse. This will change the values "Neutral Red", "Neutral Green" und "Neutral Blue" on the "Color" tab, the amount of change depends on those factors like treatment of the film (storage time and temperature) and processing in the lab.
   
   
   After white balance (right click on the small white or grey houses)
   
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7. Scan:
   Regardless of the lighting conditions, shutter speed and aperture of each frame in the roll, you should use these fixed values for exposure and film base color for scanning all frames on that particular roll of film.
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8. Image processing (?):
   Color negative film is able to capture a much wider range of intensities than slide film. Slide film maps a density range of 0:2.7 to an intensity range of 1:500, but negative film maps a smaller density range of 0:2.4 to a larger intensity range of 1:4000.
   Imagine taking a picture of a typical outdoor scene with a bright blue sky with fluffy clouds along with a person standing in a shadow under a tree. Further, imagine taking this picture with both slide film and negative film.
   When taking this picture with slide film, the photographer has to set the exposure to either capture the details of the sky and clouds, or set the exposure to capture the details of the person standing in the shadow under the tree. Once the picture is taken of one of the two intensity ranges, there's no way to get back the other intensity range after developing the film. However, when taking this picture with a typical consumer camera with negative film, the camera will usually set the exposure so that both the details in the clouds and in the shadows are captured on the film.
   This very large range of intensity captured by color negative film results in a very flat contrast curve. This can be countered by using the "contrast" tool in an image editor, the side effect will be clipping (and thus loss of detail) in the bright and dark areas of the image. Much better results can be achieved by using the "curves" tool in the more advanced image editing software packages (like e. g. Picture Window). Contrast can by increased in the mid-tonal-range without losing too much detail in highlight and shadow areas simply by applying a "S"-shaped kurve.
   
   
   Final result after using curves, perspektive correction, unsharp masking
   
   

   New from version 8.3.xx

   • Histograms have been moved to a new location.
   • Important improvement: By selecting: Image - Graph Curve in the main menu (or by using "Curve low/Curve high" in the "Color" tab) you can tune the contrast curve either graphically or by number so the above mentioned last step of image processing can now be done directly within the scan software.

   All other steps and settings are the same as for version 7.6.46.

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