Guide · Updated
Choose a photo above and it turns black and white the way film does: on Street 400 (based on Kodak Tri-X 400) or Press 400 (based on Ilford HP5 Plus 400), behind a yellow, orange, red or green filter, with the film’s grain and its paper’s contrast. Download it as a JPEG. It runs in your browser; nothing is uploaded.
The films are the two black and white films in Clack, a film camera app for Android, ported to the browser. Clack is not affiliated with Kodak or Ilford.
01 · Steps
How to make a photo black and white
- Choose a photo. Any JPEG, PNG or WebP from your phone or computer (HEIC in Safari). It is read in your browser and never uploaded.
- Pick the film. Street 400 (based on Kodak Tri-X 400) is harder with fine grain; Press 400 (based on Ilford HP5 Plus 400) softer with coarser grain.
- Pick a filter. Yellow for skies as the eye sees them, orange or red to darken them, green for foliage, none for the film as it is.
- Download. A JPEG up to 1600 px on its long side. Hold “Hold for the original” to compare first.
02 · Color into gray
Why film black and white looks different from a grayscale
Turning a photo black and white means deciding how much each color counts toward the gray. A grayscale (desaturating, or most apps’ black and white filter) uses the eye’s sense of brightness, where green counts most and blue least. Black and white film sees differently: it is more sensitive to blue than the eye is, so blue skies print pale. A colored filter on the lens changes the mix again, lightening its own color and darkening its opposite.
| Conversion | Red | Green | Blue |
|---|---|---|---|
| A plain grayscale (the eye’s brightness, Rec. 709) | 21 % | 72 % | 7 % |
| Tri-X 400, no filter | 21 % | 37 % | 42 % |
| Behind a yellow filter | 34 % | 60 % | 6 % |
| Behind an orange filter | 56 % | 43 % | 2 % |
| Behind a red filter | 93 % | 6 % | 2 % |
| Behind a green filter | 2 % | 92 % | 7 % |
The share of the gray from red, green and blue: the eye’s weights, then Clack’s model of Tri-X 400 from Kodak’s data, bare and behind each filter. A red filter makes the gray almost all red, so a blue sky has little left to print and goes dark. What each filter does and when to use it is in our guide to black and white filters.
03 · The films
Street 400 and Press 400
Street 400, based on Kodak Tri-X 400, is the harder of the two, with a fine grain and a little crispness. Press 400, based on Ilford HP5 Plus 400, is softer, with a coarser grain. Both are modeled from their makers’ published curves and color sensitivity, and printed on black and white paper. The filter keeps the exposure, as a meter behind the lens would, so you see what the filter does to the colors, not the stops it costs.
A filter on a finished photo works from the phone’s colors, which are already processed; in Clack the filter and the film come first, before the phone’s look. For color films, use the film filter.
Questions
- How do I make a photo black and white?
- Choose it above: it is converted on Street 400 behind a yellow filter at once, and you can change the film and the filter, then download it. In a phone’s gallery or any editor, a black and white filter or turning saturation to zero does it too, but as a plain grayscale, without film’s color response or grain.
- What is the difference between grayscale and black and white film?
- A grayscale weighs red, green and blue as the eye sees brightness, so green counts most. Black and white film sees blue more strongly than the eye: on Tri-X, blue makes up about 42 % of the gray against 7 % in a grayscale. So skies print paler on film, which is why photographers put a yellow, orange or red filter on the lens.
- What does a red filter do to a black and white photo?
- It passes red and stops most blue and green: a blue sky goes dark, near black in a deep blue, and clouds stay white; skin, lips and red things go light. Behind a red filter, red makes up about 93 % of the gray in Clack’s model of Tri-X.
- Is my photo uploaded?
- No. It is decoded and converted by your browser, on your device, and the page sends nothing anywhere.
- Can I turn a black and white photo back into color?
- Not with this tool: once the colors are gone, the gray does not say what they were. Colorizing guesses them, which is a different kind of tool.
- Is the converter free?
- Yes. No sign-up and no watermark; the photos you make are yours.
Sources
- Kodak Tri-X 320 and 400, technical data F-4017 (filter factors)
- Ilford HP5 Plus, technical information
- Kodak, WRATTEN 2 filters (transmittance data)
- Wikipedia, Relative luminance (the eye’s weights, Rec. 709)
- Wikipedia, Photographic filter
The percentages are Clack’s film model (filmData.ts), the same numbers as the black and white filters guide. The converter is Clack’s shader, ported to WebGL2.