These files can be used with the process described in my post Scanning Color Negative Film
Details on the process are in the post linked above.
To process a color negative scan you will need:
ACEScg-elle-V4-g10
from elles_icc_profilesThe main steps to the process are:
density balance.js
is a photoshop script that calculates density balance and automates the creation of adjustment layers from two gray color samples. It can be used with a film photo of a color checker.
To use the script and create an action:
density balance.js
script with: File > Scripts > BrowseColor Lookup
adjustment layer with inverse_01.cube
The process can be baked into a 3d lut that can be used directly in acr/lightroom.
The python script neglut.py
will generate a 3d lut cube file that will:
The lut is limited in what it can do, but can be very useful for quickly getting a finished image or flat positive for editing. The only adjustments that can be used are Exposure and White Balance. Changing any other setting would disrupt the linearity of the negative.
After you have decided on values to use for density balance in the ACEScg color space, Open the python file in a text editor.
redScale
, greenScale
, and blueScale
to your density balance values.savename
to the film name or filename you want to use.paper
to True or False, for whether or not you want to use the paper curve.# values for density balance in ACEScg
redScale = 1.0
greenScale = 0.807
blueScale = 0.579
savename = "ektar" # film name
paper = False # True / False: use paper lut
Run the script and it will write the .cube file.
To make a profile in Adobe Camera Raw or Lightroom:
file | lut | function | input | output | input range |
---|---|---|---|---|---|
inverse_01.cube | inverse | $\frac{0.01}{x}$ | linear(negative) | linear | 0-1 |
density.cube | transmittance to density | $\log_{10}(\frac{1}{x})$ | linear(negative) | density | 0-1 |
10^x.01_4.cube | density to luminance | $10^{x}\cdot 0.01$ | density | linear | 0-4 |
inv_density.cube | inverse density | $\frac{1}{10^{x}}$ | density | linear(negative) | 0-4 |
paper_a.cube | paper print curve | density | linear | 0-3 | |
paper_invert.cube | paper print curve | linear(negative) | linear | 0-1 |
A lut to simulate the response curve of photographic paper.
Use an exposure adjustment layer before this lut to adjust exposure and contrast.
paper_a
: use in place of 'density to luminance'. offset controls exposure, exposure controls contrast
paper_invert
: use in place of 'inverse'. exposure controls exposure, gamma controls contrast