So, finally deal with those negatives and slides in dusty cabinets, right? A dedicated scanner is probably the best choice but will put you into trouble when color problems are combined with huge amounts of negatives; it may be too much work to enhance every picture manual. So here is my humble attempt to make life easier. Automation is the keyword. An example of a rotten negative before and after:
Now this article will become a little larger than I first intended so here is a TOC:
Contents
General information
Software
The software in this article is based om the GIMP for image editing. See http://gimp.org/downloads/ for download links.
Platforms
If you're a typical Windows user you may use some of the solutions like basic GIMP editing. However you'll run into trouble with scripts from the command line. You may want to download and install http://www.ubuntu.com/ and dual boot your PC.
Negative color itself
Color negatives look orange. If you scan a piece of a negative between two pictures you'll notice that the positive color of the negative is ~0,44,0 (RGB values) which is the 'black' between the frames. The inverted value is (255 minus value) ~255,211,255, looking a bit orange if you have the negative in your hand and rose after being scanned.
This orange film color results in the greenish appearance of all scanned negatives and is a first step to solve. There are several ways to do this but finally the curves tool is best for this purpose. select green and pull the curve down to the location as shown here. The result is at the right. You may want to do the same for the red channel, pulling it down just a little. I have no idea why the borders are still a bit redisch - see for yourself - after correcting the green channel. The last one is after applying more settings, improving the final result.
Hardware: the scanners
Plustek OpticFilm 7400
Hardware is fine but the software..., no drivers for GNU/Linux. Don't make the mistake I made, buy another one. Anyway, I just want to scan 'as is' so included fancy shrink wrap packages are not appreciated.
IF SOMEBODY FROM PLUSTEK READS THIS: GET FREE DRIVERS FOR LINUX
Image editing: everything automagic
After 200 negatives you refuse to edit anymore. Time for a different approach and ask the Gimp far a helping hand. Automating this may be very helpful. After doing tests with several images it turns out that 'color' > 'auto' > stretch contrast' eliminates color impurities caused by the negative color itself and white balance issues. It leaves space for further modification and that is the easy and hard part. Easy is the fact 'colors' > 'curves' does the rest, simply move the left bottom point to the right. Hard is the question "how much?" is enough as a common denominator. There is no golden rule for this, what is good for a picture on the beach simply ruins a picture in a dark setting. It is dependent on the histogram, a Gimp hacker may be helpful.
At http://www.gimp.org/tutorials/Basic_Batch/ there is a nice example, good enough for modification. read the link to understand what follows.
The command-line becomes something like:
wiebe@beppe:/data/tmp/test/exedir$ gimp -i -b '(batch-post-scan "*.TIF")' -b '(gimp-quit 0)'
In ~/.gimp/scripts you should put the following file batch-post-scan.scm:
(define (batch-post-scan pattern
)
(let* ((filelist (cadr (file-glob pattern 1))))
(while (not (null? filelist))
(let* ((filename (car filelist))
(image (car (gimp-file-load RUN-NONINTERACTIVE filename filename)))
(drawable (car (gimp-image-get-active-layer image)))
)
(gimp-levels-stretch drawable)
(gimp-file-save RUN-NONINTERACTIVE image drawable filename filename)
(gimp-image-delete image)
)
(set! filelist (cdr filelist))
)
)
)