In this post I’m going to show you how to invert colour negatives in Photoshop.
You’ll also see how to remove the orange mask from 35mm colour film.
Why. Because inverting scans from colour negative film can be frustrating. The results often lack the vibrant colours and good contrast you see from professional film labs.
It gets better:
The results you get will exceed those from some professional film labs.
I will also demonstrate how to invert colour negatives in Photoshop using a photo of the X–Rite ColorChecker, so you can judge the results for yourself.
And this simple technique will work with 35mm black & white film.
The problem with inverting colour negatives
Photos from daylight-balanced 35mm colour film shouldn’t have a significant colour cast. Look at examples from a decent lab: https://www.meinfilmlab.de/en/. Greys look neutral, colours are vibrant and, contrast is punchy!
The biggest challenge to achieving vibrant colours and good contrast from 35mm film scans is successfully removing the orange film mask. When this is done, greys look neutral and the image has no visible colour cast.
I have used many inversion techniques (both paid and free) for processing 35mm film. I use this method now, because:
- It’s quick,
- Produces results better than some film labs.
With that, here are the 4 steps to invert colour negatives in Photoshop:
- Clip the colour channels using Auto Tone
- Apply a gamma correction curve to boost brightness/contrast
- Remove the remaining colour cast to make the mid-tones neutral
- Invert the image
Note: this method works best with negatives saved as linear TIFF files. For all other files, omit step 2 (apply a gamma correction curve), and proceed to step 3 (remove the remaining colour cast).
Step 1. Clip the colour channels using Auto Tone
Open the image in Photoshop and press the Auto Tone command. You have now clipped the endpoints of the red, blue, and green colour channels. Most of the colour cast has now gone, but not all. Look at the R, G, and B values for a neutral tone in the image. The three values will not be equal (and they should be). We will remove the remaining colour cast in step 3.
Step 2. Apply a gamma correction curve to boost brightness/contrast
Next, apply a gamma correction curve using a curve adjustment layer. We do this because we are working with a linear file. To convert a linear to a non-linear file with a gamma value of 2.2 (the standard gamma value for Windows), we shift the mid-tone grey value from 128 to 186. Perform this step if you work with linear files. Skip this step if you work with non-linear files (e.g., raw files taken with SLR cameras).
This step also boosts the brightness and contrast in the positive image.
Note: correcting the gamma of the image using the Levels or Exposure commands will not be as effective.
Step 3. Remove the remaining colour cast to make the mid-tones neutral
A colour cast is not a characteristic of daylight-balanced colour film.
Now you want to remove the remaining colour cast in the image because neutral tones will not be neutral if you just use Auto Tone.
To do this, select a part of the image that you know is middle grey using the Colour Picker tool. I’m using the 18% grey patch on the X-Rite ColorChecker. This step will also work if you select a region in the image that you know should be neutral (e.g., dark shadows, black/grey clothing, grey skies).
Lastly, open the Curves Dialog Box and move the mid-tone input level for the R, G, and B channels until they are all equal (keeping one of them the same). It is that simple! Middle greys will now be completely neutral.
Step 4. Invert the image
Finally, turn the image into a positive image using the Invert command. Job is done! The colours are now opposite to those you have been working with. Edit further if you like for personal taste.
Note: you can record the steps above so that you have an action set that can be used to batch process a bunch of files from the same roll of film.
Life’s too short to mess around getting your photos to look perfect. Especially when results vary from different labs, machines, and operators.
To prove this technique works, here are some more colour photos I inverted using the technique outlined above.
And here a photo of the ColorChecker I inverted using the steps above (top image), and the same image from a high street film lab and a Fuji Frontier SP-3000 film scanner (bottom image).
Note: the washed-out colours and poorer dynamic range in the lab scan. Some people may prefer the lab scan – and why not! I liked it originally until I had something to compare it with.
First Image (my scan); Second Image (lab scan).
Yes, some of the lab scans are shocking! Poor tone and weak colours.
Note: these scans are from a high street film processing store. Results from a professional film lab will be much better.
And please remember, the purpose of this post is to demonstrate how you can achieve good results at home because knowing how to invert colour negatives in Photoshop can be frustrating!
It gets better:
You can invert 35mm black & white film scans using this method. Just omit step 3. See for yourself!
Black & White Samples
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