What is an ARW file?

ARW is a container: a wrapper that holds streams encoded by something else. It stores a grid of pixels, so enlarging it past its own resolution softens it. It is used for photography and editing.

The extension is .arw, and the full name is Sony Alpha Raw. Both matter less than what the file can hold, which is what the rest of this page is about.

Sony published it in 2005. It comes out of Sony Alpha bodies bodies.

Age is worth knowing here for one practical reason: the older a format is, the more programs have had time to learn it.

Reading it outside the vendor’s own software depends on work done by other people, usually by inspection rather than by documentation. That mostly works and occasionally does not, which is the reason to convert anything you intend to keep.

ARW stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.

ARW has nowhere to record transparency. Anything transparent in the source is filled with a solid colour on the way in — white, unless something chooses otherwise.

Up to 14 bits per channel. It can work in RGB.

More than eight bits per channel is what stops a gradient from stepping when it is edited, which is why it matters in a working file and rarely in a finished one.

Adobe Lightroom, Capture One and darktable read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

ARW can hold EXIF, XMP and GPS coordinates.

The GPS coordinates are the field worth thinking about before sending a file anywhere: they say where the photograph was taken, and almost nothing warns you that they are still in there.

ARW is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

The recurring complaints: programs often show an embedded preview rather than the real data and support outside its home ground is uneven.

None of these is a reason to avoid the format. They are the things worth knowing before you are surprised by one, which is a different claim and a more useful one.

ARW is what every Sony camera writes when set to raw — the Alpha mirrorless bodies, the older DSLRs, the RX compacts. Canon writes CR2 and CR3, Nikon writes NEF, Olympus and OM System write ORF. Each manufacturer keeps its own, and none of them are interchangeable.

That fragmentation is the reason a raw file is harder to open than a JPG. There is no single raw format to support; there are dozens, each undocumented, each changing when a new camera ships. Software has to be taught every one of them individually.

An ARW holds the readings from the sensor before anything has been decided. No white balance applied, no contrast curve, no sharpening, no colour interpretation — just one brightness value per photosite, arranged in the mosaic pattern the colour filter imposes.

Turning that into a picture requires demosaicing, and different software does it differently. This is why the same ARW opened in Lightroom, Capture One and Sony’s own tool produces three subtly different images, none of them wrong. The file is the measurement; the photograph is an interpretation of it.

Sony bodies record 14 bits per channel — 16,384 brightness levels — dropping to 12 in some continuous-shooting and silent modes. A JPG has 256. That difference is the entire practical case for shooting raw.

It means a badly exposed shot is frequently recoverable. Three stops pulled back out of a blown sky, or shadows lifted without them turning into coloured mush, are routine operations on an ARW and impossible on the JPG from the same shutter press. Once the camera has written a JPG, those levels have already been thrown away.

This is the Sony-specific thing worth knowing. For years Sony’s only raw option was a compressed ARW that is not lossless — it applies an eleven-bit delta encoding within blocks of pixels, and on very high-contrast edges it can produce faint posterised artefacts.

In ordinary photographs it is invisible and the debate was mostly theoretical. It becomes visible in the specific case it was criticised for: a hard bright-to-dark transition, such as a branch against a bright sky, pushed hard in editing. Photographers found it, Sony was pressed about it for years, and it is the origin of the compression menu that newer bodies carry.

Newer Alpha cameras offer three settings and the difference is substantial. Uncompressed runs around 50 to 120 MB per frame depending on the sensor. Lossless compressed gives an identical image at roughly half that. Lossy compressed is smallest and is the old scheme.

Lossless compressed is the sensible default and there is no reason to shoot uncompressed instead — the files are simply larger for the same pixels. The one caveat is that lossless compressed ARW is newer, so older software occasionally does not read it while handling the uncompressed variant from the same camera without complaint.

Every new Sony body writes a slightly different ARW, and support has to be added to each program that reads them. Adobe, Capture One and the open-source libraries all publish updates, and there is a gap between a camera reaching customers and that update arriving — historically weeks to a couple of months.

So a brand-new camera produces files that established software rejects as unrecognised, which reads like a broken file and is not. The workarounds are to wait, to update, or to convert to DNG, which is a documented format everything already understands.

Every ARW embeds a full-size JPG preview — the image shown on the camera’s screen, with Sony’s own processing applied. It is why an unsupported ARW still shows a thumbnail in a file browser, and why the picture sometimes appears to change as software finishes loading: the preview is replaced by the real conversion.

It is also a useful escape hatch. If a file will not open properly, the embedded JPG can usually be extracted, giving a usable image at full resolution while the raw waits for software support. It is a fallback, not the raw file — none of the editing latitude is there.

A great deal. Camera model and serial number, lens, focal length, aperture, shutter speed, ISO, the exact date and time, the shooting mode, and — if the camera was paired with a phone or has a receiver — the GPS coordinates.

Almost none of it survives a conversion to JPG or PNG in the way people assume: the exposure details usually carry across and the location may or may not, depending on the tool. If a photograph is going to be published, the location deserves a deliberate decision rather than a hopeful one.

For sharing, printing or handing to a client, convert to JPG at high quality — the result is a photograph rather than a measurement, and it opens everywhere. For further editing outside a raw workflow, or where every pixel must be preserved, convert to PNG or TIFF and accept the size.

Keep the ARW regardless. The converted file has had the white balance, the contrast curve and the colour interpretation baked in permanently, and those decisions cannot be revisited. The raw file is the negative, and there is no way to make another one.