Inverting a Negative


Today’s Question: I have scanned a [color] negative into Lightroom. I have tried to use the Tone Curve to turn it into a positive without success. Is Tone Curve the best approach or is there something else I should be doing?

Tim’s Quick Answer: Within Lightroom, the Tone Curve adjustment is your best option for inverting a scanned negative to convert it to a positive image. However, because of the sophisticated adjustment that will likely be required, you may be better off re-scanning the image using the software included with your scanner to convert from a negative to a positive image.

More Detail: While it is simple to invert an image from a negative to a positive (or vice versa), a photo captured on negative film doesn’t represent a simple inversion of the original scene. Therefore, a more sophisticated adjustment will be necessary.

To begin with, there may be some overall tonal variations in the negative that need to be compensated for when inverting to a positive. The bigger problem, however, is going to be color. Color negative film generally includes an “orange mask” that is designed to help improve color accuracy in the original capture. Of course, that orange mask can also lead to problematic color in the direct scan of the film (as opposed to producing a photographic print with a chemical process).

A very basic inversion of the negative image can be created with the Tone Curve in Lightroom. First, make sure you are in the Point Curve rather than Parametric mode for the Tone Curve. In other words, you want to be sure that the Highlights, Lights, Darks, and Shadows sliders are not visible below the Tone Curve itself. If those sliders are visible, click the Point Curve button at the bottom-right below the Tone Curve to switch to Point Curve mode.

Then simply drag the black endpoint from its position at the bottom-left of the Tone Curve up to the top-left corner, and drag the white endpoint from its position at the top-right of the Tone Curve down to the bottom-right. This will create a straight-line line for the Tone Curve going from the top-left to the bottom-right, and representing a tonal inversion of the photo.

At this point some fine-tuning of the overall tonality may be necessary, but the more significant issue is going to be the color. To be sure, you could make some general progress using the Temp and Tint sliders to adjust the overall balance of colors. But in reality you are going to need to apply some careful adjustments to the overall colors in the photo.

There are two approaches you can use here, and in many cases you’ll want to use both approaches to correct the color for a scanned negative. The first is to apply a Tone Curve adjustment for each individual color channel. For each channel (red, green, and blue) you’ll need to apply a Tone Curve to shift the balance of colors within the photo, with a different shift commonly needed for the shadow areas versus the highlight areas.

You can also improve the color with the Hue, Saturation, and Luminance sliders in the HSL section of the right panel in the Develop module, shifting the Hue (overall color balance), Saturation (color intensity), and Luminance (color brightness) for each individual color.

It can take considerable work to get the color just right when working with a scanned color film negative. In most cases, the software included with your scanner will provide you with a much better starting point for a scanned negative. Even though each film stock has different issues related to overall color, most scanner software does a good job of providing a reasonably good starting point for the image in terms of the overall tone and color quality of the initial film scan. In other words, you may find that it is much less work to go back and re-scan the original negative rather than applying some sophisticated adjustments to your initial scan.