Open a
.RAW file.

.CR2 · Canon

CR2 is Canon's RAW format from 2004 until CR3 replaced it. Most Canon DSLRs of that era write CR2, and a great many of them are still working. If your files are older than about 2018, this is almost certainly what you have.

CR2 is a TIFF container with the sensor data stored inside it as lossless JPEG. That pairing is why a CR2 is appreciably smaller than the raw readout it came from while nothing has been discarded: it is compressed, not reduced.

It covers the whole Canon DSLR era. The 5D and its three successors, the 7D, the 6D, the two-digit bodies from the 20D to the 80D, the Rebel and xxxD line, and the 1D professional cameras all write it. If your files came out of a Canon and predate about 2018, this is what you have.

The first CR2 files were 12-bit. Fourteen arrived in 2007 with the 1D Mark III and the 40D and stayed, which is four times as many tonal steps to work with when you lift a shadow — and the single most useful thing to know about the age of a Canon file.

CR2 is old enough that most systems ship something for it, so outright refusal is rarer here than elsewhere. The commoner failure is quieter: your viewer shows the JPEG preview Canon embedded in the file, at a size that looks convincing, and then will not let you recover a highlight — because it never decoded the RAW at all.

.CR3 · Canon

CR3 is the RAW format Canon has written since 2018, when it replaced CR2. Canon's mirrorless bodies write it - the EOS R line among them - as do the later DSLRs. It is a newer container than CR2, which is why older software often refuses it.

CR3 is not a new version of CR2 so much as a different kind of file. Canon left the TIFF container behind and moved to the ISO Base Media File Format — the same box structure that holds an MP4 — with the image data in a new codec called CRX. That is why software which had opened every CR2 you ever shot failed on the very first CR3: there was nothing to extend.

The format carries two compression modes and the camera menu chooses between them. Plain RAW is lossless. C-RAW is lossy and lands about thirty to forty per cent smaller at the same resolution, which is a real saving and a real decision.

Every EOS R body writes it — the R, RP, R5, R6, R3, R7, R8, R10 and R50 — along with the last DSLRs, the 90D and 250D, and the EOS M50 that introduced it.

This is the format most likely to be refused outright rather than badly. It arrived in 2018 inside a container nothing else in photography used, and open decoders took years to work it out. An operating system that shipped before your camera has no CRX decoder at all — and for an OS a few versions back, no update is coming that adds one.

.CRW · Canon

CRW is Canon's first RAW format, from the earliest EOS digital bodies. It predates CR2 and is the format most likely to have been abandoned by whatever program you tried first. The files are old; they are not unreadable.

.NEF · Nikon

NEF - Nikon Electronic Format - is what every Nikon body has written since 1999. Both the DSLRs and the Z-series mirrorless bodies use it. It has changed a great deal internally over twenty-five years while keeping one extension.

NEF is the oldest RAW format still in daily use. Nikon has written it since the D1 in 1999 and the extension has not changed in twenty-five years, which is a quiet achievement and a small trap: what is inside has changed a great deal.

A NEF can be uncompressed, losslessly compressed, or lossily compressed, and that is a menu item rather than a property of the format. Two files with the same extension, from two bodies, can be built quite differently — which is why software sometimes opens one Nikon file and not the next.

The Z8 and Z9 added High Efficiency modes, HE and HE*, built on intoPIX's TicoRAW codec. They bring a full-resolution frame down to roughly 22 and 33 MB respectively. They are also, being the newest thing in a twenty-five-year-old extension, the NEFs most likely to be turned away.

The extension is the problem here. Your system has decoded NEF files for two decades, so nothing warns you that this NEF is different — a High Efficiency file from a Z9 has almost nothing structurally in common with a D700's, and a viewer that opens one may simply fail on the other with no explanation worth reading.

.NRW · Nikon

NRW is the RAW format Nikon uses on its compact cameras. It is a relative of NEF rather than the same thing, which is why some software opens one and not the other.

.ARW · Sony

ARW - Sony Alpha RAW - is the format the whole Alpha line writes. Every mirrorless Alpha body produces it, and it is one of the most common RAW formats in circulation.

ARW arrived in 2006 with the Alpha A100, the first camera Sony shipped after taking over Konica Minolta's SLR line, and it replaced the SRF and SR2 formats the earlier Cyber-shots had used.

Its compression has a history worth knowing. For roughly fifteen years Sony's compressed ARW used an 11+7-bit delta scheme — eleven bits of base value plus a seven-bit offset — which is lossy, and which put visible posterisation on high-contrast edges under exactly the conditions photographers noticed. Properly lossless compression only arrived in 2021, on the A1 and the A7 IV among others.

The whole Alpha line writes it: the A7, A7R and A7S families, the A9 and A1, and the APS-C A6000 series. It is one of the most common RAW formats in circulation, which is also why so much half-working software claims to read it.

ARW has been through several internal revisions under one unchanging extension, so age is what decides. Something that reads an A7 II file happily can refuse the file your current body writes, and the error will say nothing about which of the two it did not understand.

.SRF · Sony

SRF is the oldest of Sony's RAW formats. It comes from the early Cyber-shot cameras and is now genuinely rare - which is precisely why the files are hard to open when you find them.

.SR2 · Sony

SR2 is an early Sony RAW format, used before ARW settled in. You will meet it on Cyber-shot bodies of the mid-2000s. Support for it has quietly disappeared from most current software.

.RAF · Fujifilm

RAF is Fujifilm's RAW format, and it is unlike the others. Which RAF you have depends on the body. The GFX medium-format line and the X-A series use ordinary Bayer sensors. Most X-series bodies carry an X-Trans sensor instead, whose colour filter array is a 6×6 pattern rather than the Bayer grid — a layout that needs a demosaic written specifically for it. Rawnd has one, so both kinds open here.

Fujifilm has written RAF since the FinePix S1 Pro in 2000, which makes it one of the older RAW formats still in daily use. The extension never changed; what changed underneath it is the sensor, and that is the part which decides whether any given piece of software can open the file in front of you.

X-Trans arrived in 2012 with the X-Pro1. Instead of Bayer's repeating 2×2 quartet, Fujifilm laid out a 6×6 pattern with green pixels in every row and every column, so the sensor could drop its optical low-pass filter without printing moiré across fabric and brickwork. It works — and it also means every demosaicing algorithm written for Bayer is inapplicable to it, not merely suboptimal.

That is why X-Trans is a real dividing line between programs rather than a checkbox on a feature list. A decoder can parse the container perfectly and still have nothing to show you until someone writes a demosaic for that particular mosaic. Rawnd carries one, and it runs in the browser: the 6×6 mosaic is interpolated on your own machine, with nothing uploaded and no conversion step standing between you and the picture.

The hard part is colour rather than detail. Only eight of every thirty-six photosites read red and eight read blue, so those two channels are rebuilt from sparse evidence — and a naive interpolation paints false colour along anything finer than the mosaic itself, which is why a twig against a bright sky can come back green or magenta. Getting that right is most of the work in an X-Trans decoder, and it is why the format took years to be handled well anywhere.

.DNG · Adobe

DNG is Adobe's open RAW format, published in 2004 and adopted by many makers. Leica, Ricoh, Sigma and a number of drones and phones write it directly. Converting another RAW to DNG also produces one.

DNG is the only format on this list that is not a manufacturer's private container. Adobe published the specification in September 2004, built on TIFF/EP, and left it open — anyone may implement it, which is exactly why the oldest software you own is likelier to read a DNG than a CR3.

Plenty of cameras write it straight to the card: Leica, Ricoh and Pentax, Sigma's fp bodies, Hasselblad, DJI's drones, and Apple's ProRAW on recent iPhones. It is also what the Adobe DNG Converter produces from something else, so a DNG in front of you may be an original or a conversion, and the file does not always make that obvious.

There are two shapes of DNG and the difference matters. One holds the sensor's undemosaiced mosaic, exactly as it was read — a real negative. The other holds a demosaiced linear image, which has already had a decision made on your behalf that you cannot take back.

DNG is the format an old system is most likely to open, being published and twenty years old. When one does fail it is almost always a recent file rather than an old one — a ProRAW frame from a current iPhone, or a 16-bit DNG from a phone's expert mode — using parts of the specification that were added after the software reading it was written.

.RW2 · Panasonic

RW2 is the RAW format of Panasonic's Lumix cameras. The Micro Four Thirds bodies and the full-frame S series both write it. Older Lumix cameras used a plain .raw extension instead.

.ORF · Olympus

ORF is the RAW format of Olympus, now OM System, cameras. The OM-D and PEN bodies write it, as do the current OM System cameras that followed them.

.PEF · Pentax

PEF - Pentax Electronic Format - is what Pentax bodies write by default. Pentax cameras can usually be set to write DNG instead, which is why a Pentax card sometimes holds both.

.SRW · Samsung

SRW is Samsung's RAW format, from the NX cameras. Samsung left the camera business, and support for SRW went with it in a good deal of software. The files themselves are fine.