About
Rtro - Analog Lab · iOS
01The whole chain, not a colour grade
A real print passes through four physical transformations: light falls on the emulsion and leaves a latent image, chemistry develops it into silver density, the density is printed onto paper, and the paper is scanned back into numbers. Rtro builds a separate model for each of those four stages. It does not take the shortcut of one global filter; the frame walks the whole darkroom in code.
02Colour comes from exposure, not from a lookup table
Every pixel of a digital photograph is, at heart, three discrete numbers: red, green and blue. Rtro traces them back into a continuous spectrum and integrates it against the emulsion's sensitivity to each wavelength, which gives the light the emulsion actually absorbed. Every colour here is the result of photochemistry, not a substitution taken from a preset lookup table.
03Texture lives deep in the process, never on top of the picture
Halation, grain and diffusion are never a noise layer pasted onto the finished frame. They follow physical cause and effect, each in its own stage: halation in the gap between exposure and development, grain set into the silver density, diffusion spreading through the print exposure, and glare and micro-contrast waking up with the scanner. The effects live inside the mechanism, so nothing looks applied.
Credits
- Andrea Volpato
- spektrafilm (github.com/andreavolpato/spektrafilm) · film and paper archives (CC BY-SA 4.0, modified)
- Kenney
- kenney.nl · interface sounds (CC0 1.0)
- Mark Davis / Wordmark
- Cal Sans typeface (SIL OFL 1.1, license bundled)
- IBM
- Carbon Icons (Apache-2.0)
- Fotufilm
- fotufilm.com · grain calibration data (CC BY-SA 4.0, derived)
- Mallett & Yuksel
- Spectral Primary Decomposition, EGSR 2019
- Johannes Hanika (hanatos)
- irradiance spectral basis, 2025
- Giorgianni & Madden
- Digital Color Management, 2008
- Hung
- The Reproduction of Color, 2004
- Hurter & Driffield
- characteristic curve
- Schott / Newport
- KG3 heat-absorbing glass spectrum
- Thorlabs
- dichroic filter spectra
- ISO 2720 · CIE 15:2018 · IEC 61966-2-1
- standard references
- Dorothea Lange
- Migrant Mother, 1936 (public domain)
- Nancy Liu
- For her love and companionship.
Trademarks
Product names such as Kodak, Fujifilm and Ilford are trademarks of their respective owners. Rtro is not affiliated with, or endorsed by, any of these manufacturers.