Many of us film shooters are copying our negatives using digital cameras. Unfortunately, Lightroom doesn't contain an invert function to make a negative positive, and setting the curves to invert the image results in the sliders all working back-to-front. So I wanted a solution. I'm an ex-software guy, and currently using a Mac for my photo stuff. I'm offering the information about how I process negatives to positives, in the hope that it will help others. I'm probably not up for providing masses of support if anyone tries doing it my way. This is probably for the more geeky Mac user, if there is such a thing.
Summary of method:
I've written two bash scripts to control Imagemagick, which can produce inverted TIF files from camera raw files (in my case Sony ARW files). You CD to the directory containing your ARW files, and run ~/process_all_negs to produce TIF files that match the ARW files in the same directory.
Homebrew installed (see https://brew.sh/
Imagemagick brew installed (see http://brewformulas.org/Imagemagick
The first script, I call process_one_neg and the source looks like this:
outputfile="$(basename "$file" .ARW).TIF"
echo $file started $(date)
convert -contrast-stretch 0.25x1% -negate -colorspace Gray $file $outputfile
echo $file finished $(date)
The second script, I call process_all_negs and the source looks like this:
ls ./*.ARW | xargs -P 8 -n 1 ~/process_one_neg
I put both these scripts into my home directory on the Mac, and chmod them to be executable.
Things you might need to change:
The code above is for ARW files. If your camera makes a different type of raw file, you will need to change ARW to be that file type.
The setting "-P 8" in process_all_negs makes the computer use 8 simultaneous threads, because the CPU in my Mac has 8 threads. If your processor has more/less, you may like to change this setting.
I hope someone else finds this useful. It works well for me, and has allowed me to keep using Lightroom. Needless to say, you should use at your own risk.