# Standardized spectral and radiometric calibration of consumer cameras

## TL;DR

This paper introduces a standardized calibration methodology and database for consumer cameras, enabling improved quantitative radiometry and interoperability across devices, with practical procedures for non-experts.

## Contribution

It provides a comprehensive calibration protocol and database (SPECTACLE) for consumer cameras, addressing current inconsistencies and enabling standardized scientific measurements.

## Key findings

- High linearity in RAW data, not JPEG
- Inter-pixel gain variations over 400%
- Flat-field correction factors vary up to 2.79x

## Abstract

Consumer cameras, particularly onboard smartphones and UAVs, are now commonly used as scientific instruments. However, their data processing pipelines are not optimized for quantitative radiometry and their calibration is more complex than that of scientific cameras. The lack of a standardized calibration methodology limits the interoperability between devices and, in the ever-changing market, ultimately the lifespan of projects using them. We present a standardized methodology and database (SPECTACLE) for spectral and radiometric calibrations of consumer cameras, including linearity, bias variations, read-out noise, dark current, ISO speed and gain, flat-field, and RGB spectral response. This includes golden standard ground-truth methods and do-it-yourself methods suitable for non-experts. Applying this methodology to seven popular cameras, we found high linearity in RAW but not JPEG data, inter-pixel gain variations >400% correlated with large-scale bias and read-out noise patterns, non-trivial ISO speed normalization functions, flat-field correction factors varying by up to 2.79 over the field of view, and both similarities and differences in spectral response. Moreover, these results differed wildly between camera models, highlighting the importance of standardization and a centralized database.