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RAW Formats

Camera Raw Image Formats

Overview

RAW files are the digital equivalent of film negatives. They contain the raw sensor data before any processing. This makes them ideal for professional editing, but it also means they carry extensive metadata about your camera and shooting conditions.

The good news: most RAW formats are built on TIFF structure, so once you understand TIFF, you can navigate most RAW files. The bad news: every camera manufacturer adds their own proprietary extensions.

Open Standard

DNG (Digital Negative):Adobe's documented RAW format

Proprietary

CR2/CR3 (Canon), NEF (Nikon), ARW (Sony), ORF (Olympus)

DNG (Adobe Digital Negative)

DNG is Adobe's attempt to create a universal RAW format, and it's the only fully documented one. If you have a choice, DNG is the easiest to work with because the spec is public.

Under the hood, it's TIFF with extra tags for camera-specific color data. This makes it straightforward to parse with any TIFF-aware tool.

DNG File Structure

TIFF Header
IFD0
EXIF IFD
SubIFDs
Raw Data
TIFF Header
8 bytes
II/MM + magic + IFD offset
IFD0
500 bytes
Main image directory
EXIF IFD
1000 bytes
Camera metadata
SubIFDs
500 bytes
Reduced resolution images
Raw Data
Variable length
Sensor data

DNG Header

Byte Order (Little Endian)
TIFF Magic (42)
IFD0 Offset
OffsetHexASCII
0000
49492A0008000000
II*.....

DNG-Specific Tags

0xC612:DNGVersion
0xC614:UniqueCameraModel
0xC621:ColorMatrix1
0xC65A:CalibrationIlluminant1

Full DNG Support

PicScrub fully supports DNG files. Because DNG uses standard TIFF structure, we can remove EXIF, GPS, and other metadata using the same approach as regular TIFF files.

Proprietary Formats

Here's where things get complicated. Every camera manufacturer has their own RAW format, and while most are TIFF-based, they all have quirks. The community has reverse-engineered most of these, but documentation is scattered across various projects.

CR2 (Canon)

TIFF-based with Canon-specific IFDs and lossless JPEG compression for sensor data.

Signature: 49 49 2A 00 ... 43 52 02 00 (II + "CR" + version)
Note: CR3 (newer Canon format) uses ISOBMFF container like HEIC.

NEF (Nikon)

TIFF-based, typically big-endian (MM). Contains extensive Maker Notes with proprietary Nikon metadata.

Byte order: Usually big-endian (4D 4D)

ARW (Sony)

TIFF-based with Sony-specific modifications. Contains multiple image strips and proprietary encryption in some models.

Other Formats

  • • ORF (Olympus):TIFF-based
  • • RAF (Fujifilm):Custom structure
  • • RW2 (Panasonic):TIFF-based
  • • PEF (Pentax):TIFF-based

Embedded JPEG Previews

Something that catches people off guard: RAW files usually contain full JPEG previews. Your camera generates these so you can quickly review shots on the LCD. They're also what file browsers use for thumbnails.

Why Previews Exist

  • • Camera LCD:Quick review without processing RAW
  • • Thumbnails:File browser previews
  • • Quick edit:Faster initial load in editors

Privacy Consideration

Embedded JPEG previews often contain the same EXIF metadata as the main image, including GPS coordinates. PicScrub processes these embedded images along with the main file.

Maker Notes

Maker Notes are the wild west of camera metadata. Each manufacturer stuffs whatever they want into this blob, and the format isn't documented. Some even encrypt portions of it.

Privacy Concerns

  • • Camera serial number
  • • Lens serial number
  • • Internal firmware version
  • • Shutter count
  • • Focus point used
  • • Custom settings

Processing Challenge

Maker Notes use undocumented, proprietary formats. Some are encrypted. Complete removal requires understanding each manufacturer's format.

Manufacturer-Specific Tag Ranges

ManufacturerTag RangeNotable Tags
Sony0x7000–0x74C8SonyRawFileType, VignettingCorrection, DistortionCorrection
Canon0xC5E0CR2CFAPattern
Nikon0xC7D5NikonNEFInfo
Hasselblad0xB4C3, 0xC51BHasselbladRawImage, HasselbladExif
Panasonic0xC6D2–0xC6D3PanasonicTitle, PanasonicTitle2
Adobe DNG0xC612–0xC7A8DNGVersion, ColorMatrix, CalibrationIlluminant

How PicScrub Processes RAW

1

Identify Format

Check header for TIFF structure and format-specific signatures

2

Parse TIFF Structure

Navigate IFD chain, identify EXIF, GPS, and Maker Note locations

3

Process Embedded JPEGs

Locate and clean JPEG previews at various resolutions

4

Remove/Zero Metadata

Remove metadata tags or zero their contents

5

Preserve Raw Data

Keep sensor data and essential color/calibration tags intact

Preserved

  • • Raw sensor data
  • • Color matrices
  • • Camera calibration
  • • White balance coefficients
  • • Active area definition

Removed

  • • EXIF metadata
  • • GPS coordinates
  • • Maker Notes
  • • Embedded JPEG metadata
  • • Serial numbers

DNG Conversion

If you're sharing RAW files and want to ensure clean metadata removal, consider converting to DNG first.

Recommended Workflow

DNG conversion strips out proprietary structures while preserving the actual image data:

  1. Convert to DNG using Adobe DNG Converter (free)
  2. Process with PicScrub to remove metadata
  3. Share the cleaned DNG file

This ensures the recipient can open the file without proprietary software, and all metadata is cleanly removed.