[ismaelg]

Hi,

I'm scanning old negatives and some images have a noticeable green cast. I've tried reducing the saturation in the green channel but the contrast is heavily affected. I also tried adding red or orange filters in post process but I'm not satisfied. On another image, magenta seems to be the dominant cast. I'm I on the right track? How can I address those color casts?

Thanks,

[Nesster]

We'll need a bit more information: what type of film (and exact name if you still have that), what scanner, what scanner software?

Depending on these, there probably is a way to get better color.

[ismaelg]

Hi,
The film is Kodak Gold 100. The scanner is an old Epson Perfection 2400 photo and I'm using Vuescan.
I scan in tiff and play with the parameters to get the best possible tiff. Then try to do color correction in Photoshop CS5.

Thanks,

[Nesster]

I find vuescan very difficult to use, though if done properly it can do better than Epson software.

Try the 'set film base' technique
Advanced Workflow Suggestions
but these sites explain it better:
Scanning Color Negative Film with Vuescan
Flickr: Discussing VueScan lock exposure tutorial in I Shoot Film

[artobest]

Here is my workflow for scanning negatives: I scan them as 16-bit positives (not sure whether your scanner offers 16-bit) and set the white and black point for each channel individually to the start and end of the histogram, leaving a little headroom to prevent clipping. Then, I import the image into my image editor and invert - hey presto, a pretty good scan that usually requires only minor colour correction.

[GeneV]

I also scan BW negs as a positive. I haven't seen quite enough benefit to 16bit to merit the file size, though.

[artobest]

The file size of 16-bit scans is not really an issue on modern computers. The bottom line is, if you're planning to do significant colour or tonal correction on your scans and you care at all about quality, you have to have 16-bits to play with. I know that sounds absurdly prescriptive, but with experience it quickly becomes self-evident - it's not voodoo, it's simple mathematics. By all means store the finished scan in 8 bits though (that is, if you're confident that you can never improve it at any time in the future ).

[vladimiroltean]

About editing the black and white point for each channel, do you find too that the histogram is rather posterized (with plenty of spikes) after this process?

[wombat2go]

Hi Isma
I am starting out with the Epson V600 and trying various ways.
The best method so far:
Turn off all correction in the Epson and just scan the negs directly as color negatives (they come out as positive jpg)
From the density vs exposure graphs for the film (UMAX400):
-calculate "Reciprocal_Gammas" to bring the 3 densities back to gamma=1 ready for the gamma 2.2 out to the sRGB monitor.
B=0.57
G=0.54
R=0.52

-the Green and Red densities have to be boosted by the following ratios:
G=3/2.4=255/204
R=3/2=255/170
Blue stays at 3/3=255/255

I put all these in a preset Level file in Gimp for easy general use an all negs.
The results are not perfect but the closest of a few other ways tried.
The values work OK with 15 year old Kodak negs too.
On a neg by neg basis, it is sometimes necessary to correct the black and white levels which is easy just trimming the level line which stays with gamma=1.

[Vertex Ninja]

Try This tutorial. Make sure to scan in 16bit. (read the comments, there is some valuable pointers there)

Advanced Color Correction Tutorial that will Knock Your Socks Off!

It's best to get it close to right in the scanner first. The above tutorial should help you get an idea of what the images should look like and where to place your white, black, and gray points. Maybe try scanning the photo at low resolution, CC in Photoshop, and then go back and do a better scan using your corrected image as reference.

[artobest]

About editing the black and white point for each channel, do you find too that the histogram is rather posterized (with plenty of spikes) after this process?

Not if you scan in 16-bits.