This is a page where I will be putting up information on the software I am writing for the Mac that will convert “RAW” scanned negatives into color positives.
Update April 24, 2012: Latitude is available for a few brave souls to try. Email me for the download link.
Check out the version history for changes.
Added some keyboard shortcuts (active when the image preview is clicked on and white frame appears around it) and the ability to compare the image to a reference sample that has already been produced (lab scan, or earlier scan you made and exported).
The goal is to turn the image on the left into the image on the right….
Overview of the current user interface. On the left is a pane where open images can be selected for editing. Center pane is the image viewing pane. Right pane is where adjustments are applied.
Two tab panes. ”Film + Scanner” tab allows for adjustment variation in development, and color correction that can be readily applied across multiple negatives from the same roll, same film stock, etc. ”Image” pane applies adjustment to the positive image after it has been created by toning the negative into a positive.
Sliders allow for adjustment of the “printing” curve to turn the idealized linear response image into a best quality print. “All soft” (Left) vs “All hard” (Right) type curves compared here:
To generate the positive image from the “RAW” film scan a look up table (LUT) of the tone curve is applied. This look up table is created by profiling the film + development + scanner using a test roll of film with captures of a test target. From this data, the film+scanner response curve can be built. Shown here is the response for Ektar 100 scanned on a Nikon Coolscan 9000:
To create look up tables (LUTs) for new films+scanner combinations a series of test exposures are scanned. In “Calibration Mode” you can drag a box over the exposure patches and it will grab the values once you set the number of patches, and the exposure value (relative to others) entered as a shutter speed. In the “curve builder” window (above) you then enter in the reference exposure values for the patches. I have been using a X-Rite ColorChecker Passport. The curve is then built by the software using curve fitting relying a penalized linear least squares curve fitting algorithm.