Modes

PPRC assumes color negative film by default. Use --mode to process other film types, or to get unmanipulated linear data for another tool. For the flag itself and how to combine modes, see the --mode option.

Quick guide:

Color negative negative

The default. PPRC analyzes the whole roll to compute a shared color profile, removes the orange mask, inverts the negative, and applies a contrast stretch. The result is a neutral, data-rich 16-bit positive: a starting point with plenty of editing headroom rather than a finished, punchy look. Processing a full roll together gives the most consistent color.

Raw raw

Writes the uninverted linear sensor data as 16-bit TIFFs, with no inversion, no orange-mask removal, and no contrast stretch. Use it to hand scans off to another inversion tool such as Negative Lab Pro, ColorPerfect, or Vuescan. Tuning options (clipping, gamma, and so on) are ignored in raw mode, since nothing is adjusted.

The 16-bit shift

Pakon planar raw files contain 14-bit values from the sensor (0 to 16,383), but a 16-bit TIFF holds values up to 65,535. Written as-is, the 14-bit data would occupy only the bottom quarter of the range and look very dark, crushed against the left of the histogram. Some inversion tools may also not correctly rescale data stored this way. To make the raw files more easily digestible, PPRC multiplies every value by 4 so the data spreads across the full 16-bit range and appears more toward the center of the histogram, where you’d expect.

This step is numerically lossless. In binary, multiplying by 4 just appends two zero bits to the bottom of each value, so no precision is lost: the original value is exactly recoverable by dividing by 4. It changes the scale of the data, not the information.

Slide film (E-6) e6

For slide / transparency film, which is already a positive. PPRC applies no inversion and no orange-mask removal, just a contrast stretch, and writes 16-bit output.

Black & white bw / bw-rgb

For black & white negatives. Pakon scans are always RGB (three channels), even for B&W film, so PPRC works in RGB here too: it inverts each channel and applies a contrast stretch. bw then collapses the three channels into one by averaging them, writing a single-channel monochrome TIFF. bw-rgb keeps all three channels, writing a 3-channel RGB TIFF, which is handy if your workflow expects RGB files.

Running multiple modes at once

Request several modes in one run with a comma-separated list, e.g. pprc --mode negative,raw. Each mode’s output goes into its own subdirectory of the output folder (e.g. out/negative/, out/raw/). A single mode writes directly into the output folder.