Film Negative to Positive: Fix the Orange Cast
Turn a scan or a phone photo of a colour, black and white or slide film frame into a positive. Tap the unexposed film edge to remove the orange cast.
How to convert a film negative to a positive
- Drop in a scan or a phone photo of the negative. It opens in your browser and is turned upright if the camera stored it on its side.
- Choose Colour negative, Black and white or Slide. Only the colour negative has an orange base.
- For colour, press Tap the film base and touch the orange edge outside the frames, or press Find it for me.
- Look at the levels per channel, then move Exposure, Temperature, Tint and Contrast. Switch between Before and After to compare.
- Choose JPG or PNG and press Download positive. The file has every pixel of your photo.
What the orange base did to my test image
I do not have a lab scan to show, so I built a test image. It is 96 × 64 px, a gradient with a black unexposed edge. I turned it into a negative the way film does, by multiplying each channel with an orange mask of 230, 140 and 80 after inverting it.
Then I converted it twice. Plain inversion gave a blue picture. The tool, with the base sampled from the edge, came back within 2 of the original on every channel. A real film stock behaves less neatly than my arithmetic, and I have not measured one.
The test image, plain inversion against the sampled base
| Version | Average red | Average green | Average blue | Mean / worst error |
|---|---|---|---|---|
| Original | 122.2 | 117.2 | 120.2 | none |
| Negative with mask | 119.8 | 75.6 | 42.3 | not a positive |
| Plain inversion | 135.2 | 179.4 | 212.7 | 55.89 / 175 |
| Film base sampled | 122.2 | 117.2 | 120.3 | 0.41 / 2 |
The error is the difference per channel value, from 0 to 255, against the original. Plain inversion lifts blue by 92.5 on average and green by 62.2.
Why a simple inversion turns blue
Colour negative film carries an orange mask, so even the unexposed edge is not clear. In my test the base was 230 red, 140 green and 80 blue. Inverting subtracts from 255, which leaves 25 red, 115 green and 175 blue for what should be black. Every dark tone starts out blue.
The fix is to measure the base and divide it out of each channel before inverting. The darktable manual asks for the same thing: include some unexposed film and sample it for the D min of each channel.
What the tool does to each pixel
Colour mode computes one minus the value divided by the base, per channel. Black and white computes one minus the grey. Slide leaves the value as it is. Then levels run per channel: the result minus its black point, divided by white minus black. The points are where 0.5 % of the pixels clip at each end.
Exposure, temperature and tint are gains in linear light. Temperature 100 multiplies red by 1.32 and blue by 0.758. Contrast turns the slope around mid grey by up to a factor of two.
What it cannot do
This is not a lab scan with a real film profile. It works on the 8-bit values of a JPG, PNG or WebP, while the darktable module also has D max, a scan exposure bias and cast corrections for faded film. A faded negative, a dirty base or a scanner with its own curve will need the sliders. Dust and scratches stay in the picture.
Tips for better results
- Include a strip of the unexposed edge in the picture, as the darktable manual asks.
- Tap a clean part of the base, away from dust and from the edge of a frame.
- On a phone, lock the white balance and the exposure before you photograph the negative.
- Light the negative evenly from behind, with a light table or a white screen.
- Save a PNG if you plan to edit the positive further.
Privacy
Your negative never leaves your device. It is opened, converted and saved in your browser, and nothing is uploaded.
Frequently asked questions
How do I convert a film negative to a positive online?
Drop in a scan or a phone photo, choose the film type and tap the orange film edge. The page inverts and levels each channel. Adjust the sliders and press Download positive.
Why is my inverted negative blue?
Colour film has an orange base, so inverting turns it blue. In my test the base was 230, 140 and 80, and plain inversion lifted the average blue by 92.5. Dividing the base out first brought it back.
Can I do film negative to positive in Photoshop?
An invert command alone leaves the orange cast, so you still correct each channel with levels by hand. This page does that from one tap on the film base, then lets you adjust the result.
Does it work for black and white negatives and slides?
Yes. Black and white mode inverts the grey of each pixel, and slide mode skips the inversion and only sets the levels. Neither needs a film base sample, so the base buttons are hidden.
Is the result as good as a lab scan?
No. It has no film profile and works on 8-bit values, so it is a fast and honest starting point. A dedicated module such as darktable negadoctor models the film more closely.
Related tools and guides
- Turn a negative photo into a positive in your browser: Photograph a negative with your phone or scan it, then turn it into a positive here. Tap the orange film edge, adjust the look and save the file.
- A converter for colour, black and white and slide film: One converter for three kinds of film. Pick the type, set the levels per channel and save the positive as a PNG or a JPG.
- Image Resizer: Resize images by pixels, percentage or longest side.
- Image Cropper: Crop images to exact ratios or popular preset sizes.
- Put your photos together in one image: Join photos side by side, stacked or in a grid, with adjustable gaps and borders.
- Add text to your photo and keep it readable: Put captions on a photo with a gradient, tint or box behind them and a live contrast check.
- I Built the Tools I Kept Looking for as a Photographer: Why these browser tools exist and what I wanted from them.