.CR2

Introduction

CR2 is the raw photo format of Canon digital cameras from the mid 2000s until 2018, when Canon introduced CR3 with the EOS M50. A CR2 file holds the data read from the sensor, several previews and the camera’s settings, so the photo can be developed later with full control over white balance and exposure.

Canon has not published the format. Its layout is known from the work of independent developers, and every major raw converter reads it.

Structure

A CR2 file is built on TIFF. It starts with a little-endian TIFF header (II, 42 and the offset of the first directory), and then, at byte 8, the letters CR, the version 2.0 and the offset of the directory that holds the raw data.

Four image file directories follow. The first holds a full size JPEG preview and points to the Exif and maker note data, the second a small thumbnail, the third an uncompressed reduced size RGB image, and the fourth the raw sensor data, compressed without loss using lossless JPEG and stored in vertical slices.

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