The best way to color correct C-41 negative film scans
Updated for 2018! Reliably color correcting your scanned film negatives is an exercise in frustration. Not anymore! I've created a set of Photoshop actions that completely automates the process and will get your scanned images looking great with minimal effort and while preserving maximum image quality.
Anyone who scans their own C-41 color negatives at home has felt the pain of trying to get the correct color and contrast out of their photos. I too have felt this pain, and I've spent hours reading and researching different approaches to get the most reliable results with the least amount of effort all while preserving maximum image quality. I've figured it out and packaged a set of automated Photoshop actions for you to use that will get you a perfect color corrected image 99-100% of the time.
I have spent a long time fiddling around with different scanner software trying to get the best result out of my C-41 negatives. In the end I found that you don't need any fancy software, and it's best to use what came bundled with your scanner. In my case, that's Epson Scan, but as long as you have the option to scan as a positive image (or slide film), and you can turn off all adjustments (no color correction, no contrast adjustments, no unsharp mask), and set the color depth to 48 bit (or 16 bit per channel), then you are good to go. With all post-processing options turned completely off, it should not matter which software you use. I like Epson Scan because it's simple and easy to determine when those options are truly disabled - both VueScan and Silverfast have given me trouble in the past, but it's possible to achieve the same result with them.
This method will preserve the film's original tones as well as it's color temperature with no (or minimal - your choice) loss of color information.
Once you have your image scanned, it should look inverted and very orange, just like the negatives look in person. The goal is to remove the orange mask and get a more natural color. It works best if your scanner does not cut out all of the frame edges from your film, because you need to sample it in order to get a perfect black point for the film base. If your scanner cuts out the frame edges, you can use a piece of the film leader and scan it separately so that you can sample the orange color that way. Note that you should not include anything beyond the film edges in your image, such as the film holders or any part of the empty flatbed, as this will make color correcting much more difficult.
You should have something that looks like this:
Setting the black point
In Photoshop, sample the orange film base with the eyedropper tool. Be sure that the sample size (in the top options bar) is set to an average sample (5 by 5 for example). Click anywhere in the middle of the orange film base to sample its color. Next make a new layer and fill it by pressing Shift+Backspace, or by selecting Edit->Fill from the menu. In the Fill options, choose Foreground Color, blend mode Normal and 100% Opacity. You should see the entire screen has been filled with the orange mask color. In the layers panel, set this layer's blend mode to Divide.
Now merge the layer down by pressing Ctrl-E (or ⌘-E), then invert it by pressing Ctrl-I (or ⌘-I). You should see your image looking halfway decent, but it still has a heavy blue cast.
You should have something that looks like this:
Setting the white point
Make a new curves adjustment layer. In the curves palette, click the top-right menu button and select "Auto Options" - this is where you'll really notice a difference.
Select the "Enhance Per Channel Contrast" option, and check "Snap Neutral Midtones". Set the Shadow Clip to 0% and set the Highlight Clip to 0% as well. If you wanted to preserve as much color information as possible, you could stop here and begin working on color correcting your photo. It will likely still have a heavy cyan cast and lack contrast, but you can fix that with adjustments later. If you want a quick and dirty method and don't mind throwing away a little bit of color information, set the Highlight Clip to a very low value such as 0.05%. Play with it a little, increasing it in small increments until you're happy with the result. Keep in mind you are tossing away highlight information here, so be careful not to go too high. I usually settle somewhere around 1%, but it's completely up to you. You can also increase the Shadow Clip setting a little bit if you want more contrast, but again remember that you're throwing away color information that you can't recover later unless you start over from the original scan. How much you choose to throw away is up to you.
Further color corrections
You may be completely satisfied at this point, or your image might still have a slight color cast or lack contrast. To fix this, you can add yet another curves adjustment layer and play with each individual color channel's curve. For example, if your image looks a bit red, change the channel on the curves palette from RGB to Red and move the red curve down ever so slightly until you're satisfied. You can use the arrow keys to bump the curve up or down if you are not very accurate with a mouse or trackpad.
Some people find curves adjustments to be kind of tricky, so I will share an alternative method I learned about recently which more closely matches the method used to adjust color prints made in the darkroom. You need to make three new layers, one filled with pure yellow (255,255,0) and one filled with pure magenta (255,0,255), and another filled with pure cyan (0,255,255). Set all three layers opacity to 0% and set their blend modes to soft light. Now if your image is too green, simply increase the opacity of the magenta layer by a few percent. Likewise if your image is too blue, increase the opacity of the yellow layer by a few percent until you're happy. And if your image is too red, increase the opacity of the cyan channel accordingly.
That's it! You can always increase the contrast more using another curves layer, or by any other method you like - there are always more than one way to achieve the same result in Photoshop.
New Photoshop action
Of course I have combined the above steps into a new Photoshop action that you can download for free. If you found this guide helpful, please consider buying some film on Amazon using my referral link below. It doesn't cost you anything extra and I get a small cut.
Download the Photoshop Action here