ERF File (.erf): What It Is and How to Open It

The basics

What is an ERF file?

ERF is the raw format of one small family of cameras: Epson's R-D1 digital rangefinders. Epson announced the R-D1 in March 2004 as the world's first rangefinder digital camera. Cosina built the body, based on its Voigtländer Bessa R2 film camera, and Epson supplied the electronics and image processing. It takes Leica M-mount lenses and has a 6.1-megapixel APS-C sensor.

Camera	Released	Notes
R-D1	2004	The original
R-D1s	2006	The same hardware with new firmware; added RAW+JPEG recording
R-D1x, R-D1xG	2009	Sold in Japan only; Epson announced the end of the R-D1x in March 2014

So every ERF file was shot on one of these cameras, and nothing has written new ones since production ended. That makes ERF a rare format, but not an obscure one: rangefinder photographers still use the cameras, and the major raw developers kept their support.

Like any raw file, an ERF holds the sensor's readings before processing: no demosaicing, no white balance, no tone curve. The camera's own rendering is only in the embedded preview. That's why an ERF opened in a raw editor can look flatter than the same shot on the camera's screen.

Anatomy

What's inside an ERF file

Epson never published the ERF format; it's documented through reverse engineering. This outline uses PRONOM's signature for the format (fmt/641), which fixes the first bytes and a run of text at byte 308, and ExifTool's tag tables, which describe the maker notes and the compression. Bytes marked xx and the positions after byte 308 vary between files. No real camera file is shown or offered.

R-D1 raw file (structure outline)

R-D1 raw file (.ERF): structure outline

offset  bytes                                part
000000  4D 4D                                "MM": big-endian
000002  00 2A                                42: a standard TIFF header
000004  xx xx xx xx                          where IFD0 starts
000008  …                                    304 bytes: IFD0 entries and values
000134  45 50 53 4F 4E 20 44 53 43 20        "EPSON DSC Picture" + 00
        50 69 63 74 75 72 65 00
        53 45 49 4B 4F 20 45 50 53 4F        "SEIKO EPSON CORP." + 00
        4E 20 43 4F 52 50 2E 00
        52 2D 44 31                          "R-D1"
…       Exif IFD                             exposure, date and time
          927C  MakerNote                    → Epson maker notes
        45 50 53 4F 4E 00                    "EPSON\0": maker-note header,
                                             the same layout as Olympus's
          0280  PreviewImage                 → JPEG preview
          0400  SensorArea                   (ERF only)
          0401  BlackLevel                   (ERF only)
…       raw data                             one value per photosite,
                                             "Packed RAW" (TIFF code 32769)

14D 4D 00 2A
A TIFF header
MM (big-endian) and 42, the same start as a big-endian TIFF. PRONOM notes these are the same first bytes as TIFF/EP files and gives ERF priority over both, so identification tools don't stop at "TIFF".
2000134: EPSON DSC Picture …
The text that identifies it
Three null-terminated strings 308 bytes in: a description, the maker (SEIKO EPSON CORP.) and the model. They're tag values from the first directory. PRONOM's signature matches R-D1, which also covers the R-D1s and R-D1x names.
345 50 53 4F 4E 00
Epson maker notes
Epson's private settings start with EPSON and a null byte. ExifTool reads them with its Olympus tag table, because the layout is the same as Olympus's maker notes.
40280 PreviewImage
The JPEG preview
A JPEG made by the camera. ExifTool notes this tag in ERF files and in JPEGs from some Epson models. Quick viewers show this picture rather than developing the raw data.
50400, 0401
Raw-only settings
The sensor area and the black level, the reading that means "no light". ExifTool marks both as found in ERF files only: a raw developer needs them, a JPEG doesn't.
6Packed RAW (32769)
The sensor data
ExifTool lists Epson, with Nikon and Samsung, as a user of TIFF compression code 32769, Packed RAW: sensor values packed tightly into bytes rather than compressed. Each value is the brightness under one red, green or blue filter.

How to

How to open and convert an ERF file today

Epson's own software for the R-D1s was Photolier, plus a raw plug-in for Photoshop. These were written for the Windows and macOS versions of the time. Today the practical options are third-party tools:

Software	Support
Adobe Camera Raw, Lightroom	R-D1 since Camera Raw 2.3, R-D1s since 3.4, R-D1x since 5.4, according to Adobe's list
macOS Photos and Preview, iPhone, iPad	R-D1, R-D1s and R-D1x are on Apple's current raw list
LibRaw and tools built on it	LibRaw lists all three models; it powers Microsoft's Raw Image Extension for Windows Photos
RawTherapee, darktable	Free raw editors that read many older cameras; test your own files, since rare models get less testing

terminal

# the camera's JPEG preview, without developing the raw data
exiftool -b -PreviewImage EPSN0001.ERF > EPSN0001.jpg

# camera settings, including Epson's maker notes
exiftool -a -G1 EPSN0001.ERF

Archiving

Keeping ERF files readable

A raw format with three cameras and no published specification is a long-term risk: the Library of Congress warns that any proprietary raw format may not be supported for the long term. For ERF the situation is good today, but if the files matter, two steps help:

1Convert a copy to DNG with Adobe's free DNG Converter. DNG has a published specification and many independent readers, and it keeps the raw sensor data. DNG can also embed the original ERF, if you want a single file.
2Keep the originals next to the DNG copies. Conversion is one-way, and a future tool might get more out of the original data.

If you just need pictures, export full-size JPG or 16-bit TIFF files from a raw editor as well.

Troubleshooting

Why won't my ERF file open?

The program doesn't support raw files at all, like a browser or a basic image viewer. Use one of the tools above, or extract the embedded JPEG.
It opens as a strange TIFF. The file is TIFF-based, so a generic TIFF reader may load it and show nonsense or only the preview. Use a raw developer.
Old Epson software won't install. Photolier and its plug-in were made for operating systems of the mid-2000s. Use current raw software instead.
Colours look different from the camera's JPEG. Each raw developer has its own rendering of R-D1 colours. Adjust white balance and choose a profile, or start from the embedded preview.

Comparison

ERF vs DNG and JPEG

	ERF	DNG	JPEG
Holds	R-D1 sensor data, preview, metadata	Sensor data from any camera, preview, metadata	A finished picture
Specification	Not published	Published by Adobe	Public standard
Cameras	Three Epson models	Hundreds of models, plus converted files	Practically every camera
Edit white balance and exposure later	Yes	Yes	Only a little
Future readability	Depends on a few tools	Many independent readers	Assured

Privacy

Metadata in ERF files

The R-D1 has no GPS, so ERF files don't contain a location unless software added one later. They do contain the date and time, exposure settings and Epson's maker notes. Check with exiftool -a -G1 file.erf before sharing. ERF files contain no scripts or macros.

Sample files

There are no sample ERF files on this page. Only Epson's R-D1, R-D1s and R-D1x write them, so a real test file has to come from one of those cameras.

Put it online

Have an ERF file? Give it a link.

Drop an Epson raw file on 99helpers and it gets its own web address. Browsers can't display raw files, so anyone who opens the link downloads it to develop in their own software; add a JPEG if people just need to see the photo.

Put an ERF file online

Questions

ERF files, frequently asked

What is an ERF file?

A raw photo from an Epson R-D1, R-D1s or R-D1x digital rangefinder: unprocessed sensor data, a JPEG preview and the camera's settings in a TIFF-based file.

How do I open an ERF file?

Use Lightroom or Photoshop (Camera Raw), Photos or Preview on a Mac, RawTherapee, or Windows Photos with Microsoft's Raw Image Extension. Browsers can't open it.

How do I convert ERF to JPG?

Open it in a raw editor or Preview and export as JPEG. To get the camera's own preview instead, run exiftool -b -PreviewImage file.erf > file.jpg.

Should I convert ERF files to DNG?

For archiving, it's sensible: DNG is documented and widely supported. Use Adobe's free DNG Converter and keep the original ERF files too.

Which cameras make ERF files?

Only Epson's R-D1 (2004), R-D1s (2006) and R-D1x/R-D1xG (2009, Japan only).

Is ERF the same as TIFF?

It's built on TIFF's structure, so it starts with a TIFF header, but the image inside is raw sensor data that only raw software can develop properly.

Related formats

Other file types explained

DNG file TIFF file RAW file JPEG file PEF file RW2 file All file types

Keep going

Host an ERF file

Put an Epson raw file online at its own address.

Share an ERF file

Send a raw photo as a link instead of an attachment.

Hosting guides

How to put files, reports and sites online.

Sources

Last reviewed 27 October 2026.