What Is an ARW File? Sony's Raw Photo Format, and the Three Kinds It Writes
An ARW file is a raw photo from a Sony camera. Jump to your question below, or read it through in order.
An ARW file is a raw photo from a Sony camera. Jump to your question below, or read it through in order.
An ARW file is a raw photo from a Sony camera. ARW stands for Sony Alpha Raw. It holds what the sensor measured, before the camera turned any of it into a picture. Nothing in it has been finished.
That is why no ordinary viewer displays one, and it is why an ARW gives you room a JPEG cannot. The catch is that Sony writes three different kinds of ARW, and the one most cameras ship on throws data away.
Shoot in raw and your Sony camera skips the step where it decides how your photo should look. What lands on the card is unprocessed image data. No sharpening, no contrast curve, no white balance baked in. What lands on the card is the reading from every photosite, and the settings recorded beside it as notes rather than decisions.
Photographers call that a digital negative, and the name fits. A negative is not the print. It holds more than the print does, and something has to develop it.
Sony has written ARW files since the Sony Alpha DSLR-A100 in July 2006, and has never published a specification for the format. Everything outside Sony's own software came from reading the bytes.
.arwSony cameras do not use CCD sensors. This page said they did for years. One camera did. The DSLR-A100 of 2006 was the first Sony DSLR and the last one with a CCD.
Every Sony body since the A700 in 2007 reads its sensor with CMOS, branded Exmor. If you own a Sony camera made this century apart from that first one, no CCD was involved.
One brightness number per photosite, laid out in the Bayer mosaic the sensor uses. The color you see later comes from demosaicing at development, not from the file. That extra bit depth is what gives raw its dynamic range in shadows and highlights. Beside it sit the shot settings, the lens, the timestamp and often the location.
A full-size JPEG preview sits inside as well. That preview is what your camera shows on its screen. It is also what a file browser displays when it cannot read Sony raw, which is worth knowing when nothing seems to work.
A second, unrelated thing uses .arw. ArtStudio, an old painting program from DrawingHand, saved its pictures with the same extension. If your file came off a Sony camera it is raw. If it came out of a drawing program from twenty years ago, it is not.
Sony writes three kinds of ARW. Compressed is lossy. Uncompressed keeps everything and is large. Lossless Compressed keeps everything and is smaller. Most bodies ship set to the lossy one.
Search for an ARW file and you will be told it holds uncompressed sensor data. Two of the three directories ranking for this term say exactly that, and so did this page until today.
“It contains raw, uncompressed image data captured by the camera's sensor.”
For most ARW files in the world, that is wrong. The mix-up starts in Sony's own menu. There, Uncompressed means nothing was thrown away and Compressed means something was.
| Setting | Loses data? | Size | Arrived |
|---|---|---|---|
| Compressed | Yes, it is lossy | About half of uncompressed | 2008, with the A900 |
| Uncompressed | No | Largest of the three | 2015, with the a7R II |
| Lossless Compressed | No | Smaller, and nothing given up | 2021, with the Alpha 1 |
Sony puts it plainly enough. Lossless Compressed “causes no deterioration in image quality and has a high compression rate”. Compressed makes a file “approximately half” the size of uncompressed.
Check your camera now, not after the shoot. The setting sits under Image Quality, RAW File Type. If your body offers Lossless Compressed, that is almost always the right answer: nothing is thrown away and the files stay manageable.
Compressed raw runs the 14 bits from the sensor through a tone curve that squeezes them into 11 bits. Then it cuts the image into runs of 16 pixels per color channel. It stores the brightest and darkest value in every run, then describes the pixels between them with 7-bit differences.
When a run holds gentle variation, 7 bits is plenty. Straddle a bright edge and 7 bits stops being enough, so the differences cannot describe what was there. DPReview's teardown put it directly.
“the 7-bit values used to note the differences aren't sufficient to precisely describe the original image information”
On screen it shows up as posterization, banding in narrow stripes beside high-contrast edges. Branches against bright sky, rim-lit shoulders, stars beside black. It gets worse when you lift that area in editing, which is exactly when raw is supposed to help.
Most photographers never see it. The artifacts sit at pixel level beside hard edges, and normal scenes rarely trigger them. That is why Compressed was the default for years without much complaint. It matters when you shoot high contrast or push files hard in editing.
An ARW file is a TIFF file underneath. It opens with the same four bytes a TIFF does, and Sony's own data hides in private directories inside it, some of them enciphered.
Sony invented no container. ARW is built on TIFF and follows TIFF/EP, the ISO standard written for this job. So the outer shell is ordinary, and any TIFF reader can walk it.
Every ARW begins 49 49 2A 00, which reads as II* and marks a little-endian TIFF. Nothing in those four bytes says Sony, and nothing says raw.
What identifies the file sits further in: the string SONY in the metadata, and the Sony MakerNote directory beside it. So any tool reading only the first four bytes will call your ARW file a TIFF, and it is not wrong.
| Part | What it holds |
|---|---|
| TIFF directories | Called IFDs. Image size, bit depth and where the raw data starts |
| EXIF | Camera, lens, shutter, aperture, ISO, date, often GPS |
| JPEG preview | A full-size finished picture, plus a small thumbnail |
| Sony MakerNote | Body settings the standard has no field for |
SR2Private | Sony's own area. Partly enciphered, holding white balance and correction tables |
| The raw data | One reading per photosite, in the Bayer mosaic |
The private area is the reason free software took years to catch up on every new body. The standard parts are readable by anyone. The parts that decide how the picture should look are not.
The metadata travels with the photo. Camera, lens, timestamp and sometimes the exact place it was taken. That is useful in your own library and worth thinking about before you hand the original file to anyone else.
Free options cover almost everyone. Windows needs one download from the Microsoft Store. macOS needs nothing at all. To develop a photo rather than look at it, Sony's Imaging Edge Desktop, darktable and RawTherapee cost nothing.
Two jobs here need different tools. One is to open ARW files, the other is to develop them. Seeing your photo is one. Developing it, which means choosing the white balance and exposure your camera left open, is the other.
| Software | Cost | Why choose it |
|---|---|---|
| Sony Imaging Edge Desktop | Free | Sony's own. Color matches the camera, because it uses the same profiles |
| darktable | Free, open source | Runs on Windows, macOS and Linux. Closest free thing to Lightroom |
| RawTherapee | Free, open source | More control than most people need, which is the point of it |
| Lightroom, Adobe Photoshop | Subscription | What most studios run, through Camera Raw |
| Capture One | Paid | A Sony-specific free edition has shipped at times. Worth checking |
| ACDSee, Corel PaintShop Pro | Paid | Photo managers that develop raw files alongside everything else |
Under darktable, RawTherapee, GIMP and dozens of smaller tools sits the same engine: LibRaw, which grew out of dcraw. When free software gains support for a new Sony body, that is usually where it happened.
Sony's old software is gone, and some pages still recommend it. Image Data Converter was retired. Sony's notice reads: “Downloading of Image Data Converter has been discontinued since September, 2018.”
Imaging Edge Desktop replaced it in September 2018. Anything telling you to download Image Data Converter is pointing at a dead link, and the same lists usually name editors that shut down years ago.
Photo files reach other programs too. Heading into layered editing? Photoshop PSD documents are where an ARW usually ends up once Photoshop has it.
Searching for a free ARW viewer is riskier than it looks. The file itself is data and cannot run anything, but the download sites at the top of those searches bundle adware. Use the Microsoft Store, imagingedge.sony.net, darktable.org or rawtherapee.com.
The usual cause is the opposite of what people assume. Nothing is damaged. Your camera is newer than your software, and raw support is added camera by camera.
Most formats break in one direction: old software cannot read new files. Raw files break that way harder than anything else, because every camera model needs its own support added by hand.
Your editor does not read ARW in general. It reads ARW from its own list of camera bodies. Buy one released after your software shipped and you fall off that list.
| What you see | What it usually means | Start with |
|---|---|---|
| Unsupported camera, or file not recognized | Software older than the camera body | Update it, then read on below |
| Opens, but the edits do nothing | You are looking at the embedded JPEG preview | A developer that reads the raw data |
| No thumbnails in File Explorer | Raw Image Extension is not installed | The Microsoft Store, free |
| The DNG Converter refuses it too | A raw variant Adobe has not added yet | Sony's own software meanwhile |
| Looks flat and gray next to the JPEG | Nothing is wrong. Raw arrives undeveloped | Any raw developer |
| Truly unreadable, in everything | A part copy or a bad card transfer | The memory card, before anything else |
In December 2022 the a7R V shipped and Camera Raw answered owners with one line: Adobe Camera Raw does not yet support Sony A7R V files. Adobe added them within the week.
It happened again with the a7 V, which arrived in February 2026 with a new Compressed (HQ) RAW option. Owners reported those files loading as previews only, with no way to edit them. Adobe's own DNG Converter turned them down too. Lossless Compressed files from the same camera worked.
Just bought a Sony body? Update your raw software before the first real shoot, and shoot Lossless Compressed rather than any brand-new variant until you have seen the files open on your own machine.
There is always a way through. Sony's Imaging Edge Desktop supports a camera from the day it ships, because Sony makes both. Develop there, export a TIFF and carry on in whatever you normally use until support arrives.
Sony bodies record 14 bits per pixel, then quietly fall to 12 under certain settings. Continuous shooting is the common one, and Compressed raw is usually what triggers it.
Bit depth is how finely the camera can tell one brightness from the next one. At 14 bits there are 16,384 steps between black and white. At 12 bits there are 4,096. Both are far beyond the 8 bits a JPEG carries, and the difference shows when you pull shadows up hard.
“RAW images recorded using the following models have a resolution of 14 bits per pixel. However, the resolution is limited to 12 bits under certain shooting conditions.”
| Body | Setting | Result |
|---|---|---|
| a7 III, a7R III, a7R IV | Compressed, continuous shooting | Falls to 12 bits |
| a7 III, a7R III, a7R IV | Uncompressed, continuous shooting | Stays at 14 bits |
| a7 III family | Compressed, bulb or long exposure NR | Falls to 12 bits |
| a6400, a6600, ZV-E10 | Silent shooting on | 12 bits, single frames as well |
| a7 IV, a7R V, a7C II | Lossless compressed, any of the above | Stays at 14 bits |
| a6700 | Compressed, electronic shutter | Falls to 12 bits |
Read down that table and one pattern runs through it. Lossless Compressed holds 14 bits where Compressed does not, on body after body, which makes the setting worth more than the storage it saves.
Shooting long exposures or bursts? Check your own model against Sony's table rather than trusting the general rule. The conditions differ between bodies, and on some of them silent shooting alone is enough to halve the steps.
For comparison, a JPEG is 8 bits. Sony notes it in the same document. Even a 12-bit raw file carries sixteen times the tonal steps of the JPEG beside it. So the 14-bit question is about how far you can push a photo, not whether raw was worth shooting.
Develop first, export second. JPEG suits sharing, TIFF suits further editing and DNG suits archiving. Keep the ARW whatever you export, because the export cannot be undone.
Converting raw is not really conversion. It is development. You choose the white balance, exposure and contrast your camera left open, then write the result somewhere ordinary.
| Export to | Keeps | Best for |
|---|---|---|
| JPEG | 8 bits, lossy, small | Sending, posting, printing at a shop |
| TIFF | 16 bits, lossless, layers if you add them | More editing elsewhere |
| DNG | Everything. Still raw, still adjustable | Archiving. See what a DNG file is |
| PSD | Layers, masks, adjustment stacks | A Photoshop project |
ARW is closed, undocumented and tied to how long Sony keeps caring about old cameras. DNG is published, documented and readable by anything that reads raw at all. The Adobe DNG Converter is free and turns ARW files into DNG without developing them.
That matters more than it sounds. Sony drops support for old models eventually, and free software tracks whatever the volunteers can still test. A DNG copy of your twenty-year-old photo is far likelier to open than the ARW beside it.
A JPEG export is not a backup of a raw photo. It is one interpretation, flattened to 8 bits, with your room to change your mind removed.
Delete the ARW and keep the JPEG, and you have thrown away the negative and kept one print.
A JPEG is the camera's finished picture. An ARW is the measurement it worked from. Raw is a category; ARW is Sony's entry in it, and Canon, Nikon and Fujifilm all have their own.
12 or 14 bits per pixel. White balance and exposure still open, wide room in shadows and highlights, 25MB to 130MB, needs a developer.
8 bits per pixel. Every decision already made and baked in. A few MB, opens anywhere and the only one you can send to somebody.
Neither wins outright. Shoot raw when the light is difficult or the photo matters. Shoot JPEG when you need to hand it over in the next ten minutes. Many Sony bodies write both at once, which settles the argument.
Raw is a category, not a format. Every maker of digital cameras built their own, none of them documented it and none of them work together.
| Extension | Made by | More |
|---|---|---|
.arw | Sony | This page |
.cr2 | Canon | See the CR2 file format |
.crw | Canon, older bodies | See Canon CRW files |
.nef | Nikon | See what an NEF file is |
.raf | Fujifilm | See Fujifilm RAF files |
.dng | Adobe, and open | See the DNG format |
You cannot turn an ARW into CR2 or NEF. They come from different companies and wrap different sensors. Nothing translates between them. DNG is the only common ground, and it exists because Adobe built it.
Every one of these has the same weakness. Closed, undocumented and dependent on the manufacturer. That is why how a file format works matters when you are deciding what to keep photos in for twenty years.
One ExifTool command names the format version, the camera and which of the three kinds you have. No hex editor needed.
Sony writes the format version into every file, and ExifTool reads it straight out. It is the quickest way to settle which of the three kinds you hold.
ExifTool is free, comes from exiftool.org and runs on Windows, macOS and Linux. On a file from an Alpha 1 II the answer looks like this:
| Field | Value |
|---|---|
| File Format | ARW 5.0.1 |
| Sony Model ID | Unknown (400) |
| RAW File Type | Lossless Compressed RAW |
RAW File Type is the field that matters most. It reports Uncompressed, Compressed or Lossless Compressed RAW, which tells you in one word whether the file gave anything up.
| Version | First body | What changed |
|---|---|---|
| ARW 1.0 | DSLR-A100, Jul 2006 | The first one. 12 bits, no compression |
| ARW 2.1 | A900, Oct 2008 | Lossy compression arrives, as 11-bit values with 7-bit deltas |
| ARW 2.3 | SLT-A99, Dec 2012 | First 14-bit sensor |
| ARW 2.3.1 | a7R II, Jun 2015 | Uncompressed 14-bit arrives |
| ARW 4.0 | Alpha 1, Apr 2021 | Lossless compression arrives, using lossless JPEG |
| ARW 5.0 | a9 III, Nov 2023 | Global shutter body |
| ARW 6.0 | a7 V, Feb 2026 | A new lightweight raw variant |
Bought a used Sony body and unsure what it writes? Take one photo, run the command above and the file answers for itself. Anything reporting ARW 2.1 through 2.3 is compressed by default, and the menu will have a setting worth changing.
Sony wrote raw before ARW existed. .srf came in 2004 and .sr2 in 2005. .arq is newer and different: four ARW frames combined by Pixel Shift.
ARW did not arrive from nothing. Sony had been writing raw on Cyber-shot cameras for two years, and the Alpha line it landed on was bought rather than built.
| Extension | Arrived | What it is |
|---|---|---|
.srf | Jan 2004, DSC-F828 | Sony Raw File. The first Cyber-shot with raw |
.sr2 | Dec 2005, DSC-R1 | Version two of the same idea |
.arw | Jul 2006, DSLR-A100 | Sony Alpha Raw. What every Sony camera writes now |
.arq | Nov 2017, a7R III | Four ARW frames from Pixel Shift, combined |
ARQ is the one that surprises people. Pixel Shift moves the sensor by one photosite between frames, so every position gets real red, green and blue readings rather than guesses. Sony Imaging Edge combines the four ARW files, and the ARQ it writes is the result.
Over the winter of 2005 and 2006 Konica Minolta handed its SLR business to Sony and left cameras behind. The DSLR-A100 that followed in July 2006 succeeded the Konica Minolta Dynax 5D and was built in a Konica Minolta factory. It kept the Minolta lens mount, so existing lenses still fitted.
The traces are still in the files. Inside an early ARW sits MakerNote data laid out the Minolta way, carrying segments from Minolta's own raw format.
Found old Sony photo files that are not ARW? SRF and SR2 files are twenty years old and most raw software has quietly dropped them. Convert them to DNG for archiving while something still reads them.
Closed, private and never registered. There is no published spec and no IANA media type. Every reader outside Sony was built by reading the bytes.
You do not need this section to open anything. It is here because the gaps in it explain why the rest of the page reads the way it does.
Three things an ARW file is not. It is not a picture, so it is not editable in place the way a JPEG is. It is not JPEG, whatever the preview inside suggests. And it is not one format: the version and the compression setting both change what is in there.
| Property | Value |
|---|---|
| Published specification | None. Sony has never released one |
| Media type | None registered with IANA. No Sony type appears in the registry |
| Quoted in the wild | MIME image/x-sony-arw. The x- prefix marks a type nobody registered |
| Container | TIFF, and TIFF/EP, which is ISO 12234-2 |
| Byte order | Little-endian |
| Signature | 49 49 2A 00 at offset 0, the plain TIFF marker |
| Color filter array | Bayer RGGB, demosaiced at development |
| Bit depth | 12 or 14 bits per pixel, by body and setting |
| Embedded preview | Full-size JPEG, plus a thumbnail |
| Private data | SR2Private, partly enciphered |
The unregistered media type is not a detail. Registering one with IANA means describing the format in public, which is the one thing Sony has declined to do for twenty years.
dcraw began decoding Sony raw in 2006, within days of the A100 shipping. LibRaw grew out of that work and now sits under darktable, RawTherapee, GIMP and most free photo software. Every new Sony body means someone opening a sample file and working out what moved.
A separate volunteer project has documented the SRF, SR2, ARW and ARQ layouts in public since then. It tracks every version from ARW 1.0 in 2006 to ARW 6.0 in 2026. It exists because Sony never published the thing it describes.
That is why new cameras break old software. Nobody is withholding support. Every Sony release means the reverse engineering starts again on that body, and free software waits for volunteers who own one.
Two questions sort out most of what is left. Answer them in order.
Windows needs one free download. Raw Image Extension from the Microsoft Store, and Photos reads ARW. A Mac already does. See section 4.
Then update the software, not the file. Raw support arrives body by body, so a recent camera needs a recent version. See section 5.
Shooting another make as well? Canon CR2 files, Nikon NEF files and the Fujifilm RAF format all have the same closed-format problem on their own side.
Thinking about keeping photos for decades? DNG file archiving is the documented answer, and the TGA image format plus PCX picture files show how quickly an image format can be left behind.
Taking the photo further? The PSD file format is where layered edits live, and the PDF format is what a printer usually asks for.
Working on Windows or a Mac and stuck on the viewer rather than the file? Our Windows fixes and the macOS guides cover the system side.
New to all of this? What a file format is covers the ground underneath, and our file format guides list the rest.
Found something here that does not match your Sony camera? Send us the exact wording on screen and we will check it against the version tables.