How to Invert Colour Negatives in Photoshop
Are you reading this blog post in the hope of learning how to invert colour negatives in Photoshop? Good, because I am going to show you how to get results that exceed those from some professional film labs. I have used dozens of different colour negative film inversion techniques (both paid and free) and I use this procedure now, because: (1) it’s quick, (2) easy, (3) and produces results better than some photo labs. It’s also more accurate than anything else I have used.
Like me, you have probably been frustrated in your past attempts to invert colour negative film scans into positive images with vibrant colours and good contrast (like the pictures you get back from professional film labs).
I imagine you have also spent ages trying to remove the annoying colour cast that is often visible in the final image. Or convincing yourself that the colour cast is supposed to be there – because it’s film! Well, it shouldn’t be there. Correctly processed negatives from daylight-balanced colour film shouldn’t have a significant colour cast. Have a look at photos from a decent film lab: https://www.meinfilmlab.de/en/). Neutral tones should look neutral and colours should look accurate when captured with daylight-balanced colour film.
One of the biggest challenges to achieving accurate colours from scanned 35mm colour negatives is the successful removal of the orange film mask or neutralisation of midtone greys. When this is done properly, neutral colours look neutral and the image has no visible colour cast.
And I am going to demonstrate my technique on a photo of the X–Rite ColorChecker, so you can judge the accuracy of the resultant colours for yourself (rather than on a photo with a limited colour gamut, which makes it impossible to judge whether the technique works or not).
This method works with negatives scanned using VueScan and saved as linear TIFF files (and processed in Photoshop). People who use SLR cameras to capture negatives may still find parts of this method useful (e.g., for removing stubborn colour casts / improving tone).
The secret I have found to get an excellent inversion of colour negative film is to: (1) remove the orange film mask completely (to get accurate colours), and (2) apply a gamma correction tone curve (to enhance the brightness and contrast) before inverting the negative into a positive.
If you use the ‘Auto Tone’ command in Photoshop to remove the orange film mask (which many film inversion techniques use), you will have problems, because neutral tones will not be neutral. Try it for yourself and then 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 if you want the orange mask removed properly). Thus, the inverted image will have a colour cast, which is not an inherent characteristic of daylight-balanced colour film.
Therefore, the only way to remove the orange film mask successfully is to do it manually. But you said your technique was quick and easy – I hear you say! Fortunately, you can save this step and run it as an action set in Photoshop on a whole batch of files taken with the same film stock, and the results will still look great!
Here We Go!
Step 1. Open your file in Photoshop.
Step 2. Press ‘Auto Tone’. We have now clipped the endpoints of the red, blue and green colour channels so that most of the colour cast has gone (p.s. I have seen people do this manually, which is unnecessary).
Step 3. Before we remove the orange colour cast completely, apply a gamma correction tone curve to the image using a curve adjustment layer, where you shift the midtone grey value from 128 to 186. This step is performed because we are working with a linear TIFF file, not a non-linear file. And to convert a linear to a non-linear TIFF file with a gamma value of 2.2 (the standard gamma value for Windows), you need to shift the midtone grey value from 128 to 186. This step also improves the brightness and contrast in the positive image.
Note: Correcting the Gamma using ‘Levels’ or ‘Exposure’ commands will not be effective (I have tried!).
Step 4. Next, you want to remove the residual colour cast in the image, because as I said above – neutral tones will not be neutral if you just use ‘Auto Tone’. To do this, select a part of the image that you know should be a midtone grey value using the ‘Colour Picker’ tool. I am using a grey patch on the X–Rite ColorChecker, but this step will still work if you select a region in the image that you know should be grey (e.g., dark shadows, black / grey clothing, grey skies, etc.,). Then, open the ‘Curves Dialog Box’ and move the ‘midtone input level’ for the R channel up a little, and the B channel down a little, so that all three midtone levels are equal. It really is that simple! Midtone greys in the image will now be pure grey (i.e., neutral).
Note: Colour correction can be improved across the whole image by sampling ‘White’, ‘Grey’ and ‘Black’ tones within the image (easier if you have a photo of a ColorChecker), but is overkill in most cases. This extra work may also remove the inherent characteristic of film, where highlights can sometimes have a pink hue, and shadows a blue/green hue).
Step 5. Invert the image. Job done! Process further in Lightroom if you like for personal taste.
Record the steps above so that you have an action set saved that can be used to batch process a whole bunch of files from the same roll of film (and other files from the same film stock if they were developed at the same time). The results will be good enough. Life’s too short to mess around getting the photo looking perfect when there’s no such thing! I mean, results vary from lab, machine, and operator.
To prove this technique works, here are some other colour photos I inverted using the technique outlined above.
Colour Negative Samples
And here is another photo of the ColorChecker I inverted using my technique (top image), and the same image from a high street film lab that used a Fuji Frontier SP-3000 film scanner (bottom image). Notice the washed out colours and poorer dynamic range in the lab scan. But some people may prefer the lab scan – and why not! I liked it originally (but then I had nothing to compare it too!).
More Lab Comparisons. First Image (Mine); Second Image (Lab).
Yes, some of the lab scans are shocking! Poor tone and inaccurate colours. Note: these 35mm 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 blog post is to demonstrate how you can achieve good results at home, because for many people inverting colour negatives in Photoshop can be very frustrating! Not helped by the fact you often have nothing to compare the results with, so you do not know whether your photos are any good or not.
Oh, and my technique works with black & white film scans too (just omit step 4 above). See for yourself!
Black & White Negative Samples
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