How to turn black and white negatives into positives in Adobe Lightroom

Lightroom doesn’t have a ‘negative’ filter for turning negative images into positives, so how do you do it? I’ve been going through my old mono negatives, rephotographing them with a camera and a macro lens, and I wanted to figure out how to convert them without using an external tool – and here’s how it’s done! (And it should work in any other software with curves adjustments.)

01 My original negative in Lightroom

Here’s my negative in Lightroom. What’s interesting about using a camera and a macro lens to digitise old negs is that it turns out their tonal range easily fits within the camera’s own dynamic range, and so far I’ve not had to grapple with any shadow or highlight clipping. That’s fine – but now I have to convert this image from a negative into a positive.

02 Cropping to the negative area

There’s one thing I want to do first, though. When I scanned my negs I left a small border around them to help me check that they were straight. I want to crop this out now so that it doesn’t influence the histogram in the next steps. The simplest way to do this is to switch to the Crop tool and choose the 3:2 aspect ratio to correspond to the 35mm film format (or use ‘As Shot’ if that’s the aspect ratio you used when photographing the negative. Now all you need to do is crop out the unwanted film rebate around the edges.

03 Reversing the Tone Curve

The negative conversion is really simple! You need to swap to the Tone Curve Panel, then reverse the slope of the curve – you drag the black point control point from the bottom left corner to the top left, and the white point control point from the top right corner to the bottom right. The curve is now reversed and our negative has become a positive. This image looks pretty flat, though, so we need to fix that.

04 Maximising the contrast

We can fix the poor contrast quite easily. You’ll see from the histogram that all the tones are bunched in the middle with no proper blacks or whites – this is how most of my negatives turn out, anyway. I can fix this by dragging the top left control point inwards to line up with the tip of the histogram and then I do the same with the bottom right control point.

05 Tonal adjustments are reversed!

The one thing you have to remember when you reverse the Tone Curve in this way is that all your adjustments are reversed too. Imagine you’re looking at the Tone Curve panel in a mirror. The white point control point is now on the top left and the black point control point is now on the bottom right. So if I want to make a curve adjustment to brighten the exposure but keep the shadows dense, I need to push the curve up towards the top left, as you can see here.

If you do have a lot of old negatives you want to digitise, I do strongly recommend using a camera and a macro lens rather than a scanner. Flatbed scanners don’t really have the optical quality for scanning 35mm negs, and proper film scanners are expensive, hard to find these days, and slow to use.

For my digitising process I simply use a regular Lightbox, place the neg strips directly on top then move the whole lightbox slightly to frame up the next negative – it’s much easier to stay lined up than constantly moving the camera. Some negatives can be more bowed than others, but I place a weight on an adjoining neg to flatten it down and that seems to be good enough.

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