Sony Compressed vs Uncompressed vs Lossless RAW: 60 Files Measured (2026)

Published September 28, 2026 · Daniel Tello · RevelRaw

Sony Compressed RAW kept at most 2,029 distinct tonal values in 17 files; Lossless L and Uncompressed kept up to 16,365 on the same scenes (RevelRaw lab, 60 CC0 ARW files, 14 bodies, macOS 27.0, September 28, 2026).

Every Sony guide to this setting repeats the same three definitions and the same a7 IV frame-rate example. None of them measures the files. So on September 28, 2026, we downloaded 60 public-domain ARW files covering 14 Sony bodies in every RAW file type each one offers (except Lossless M/S on the a1 and a7C II), read what each file stores, and opened all of them on one Mac. If you're new to the format, what an ARW file is comes first.

What each Sony RAW file type does

Uncompressed. Every sensor pixel stored in full, 2 bytes per pixel, so the file is the same size whatever the scene. Sony added it in 2015 (a7S II at launch; a7R II by firmware 2.0 on October 19, 2015, per DPReview). The biggest file and, in our test, the fastest to open.

Compressed. The original Sony RAW, and the only one the a7 II, a7 III, a7R IV and a7S III offer besides Uncompressed. Sony's guides call it "approximately half" the size of Uncompressed. It is a fixed rate, and it is lossy; how it loses is in the tonal-steps section below.

Compressed (HQ). New on the a7 V and a7R VI. Sony's a7 V guide says images "can be recorded in a higher image quality than when shooting with [Compressed]" and stops there; it doesn't say how the two differ or whether HQ is lossless.

Lossless Compressed L. Full-resolution sensor data packed like a zip archive: the same values come back out, in a smaller file whose size depends on the scene. Sony's wording, on the a7 IV guide and its siblings, is that it "causes no deterioration in image quality and has a high compression rate". It arrived with the a1 in 2021 (DPReview's review calls it the first Sony Alpha with lossless RAW) and is on the bodies that followed, the a6700 included.

Lossless Compressed M and S. Reduced-resolution sizes added by firmware to bodies that already had L: a1 firmware 1.30 in June 2022 (PetaPixel), a7 IV firmware 1.10 in August 2022 (DPReview). Sony says only that they "reduce the image size, so the image resolution will be lower than that of the L size". What they store surprised us; see below.

Two rules from the same Sony pages apply to all of them: L is selectable only in full-frame, and both card slots have to use the same RAW file type.

The dataset: 60 Sony ARW files, 14 bodies, one Mac

File sizes in MB, one file per cell, 14-bit L files unless marked. * All modes shot on the same scene within a few minutes (the a9 III within about half an hour; the a7 IV with slight framing drift). Unmarked rows compare loosely: the a7R IV pair differs in exposure, and the a7 II, a7S III and a7 III files are different scenes (the a7 III's Uncompressed was shot the next day). The a7R IV and a7 III also gave us 12-bit twins; those have their own section.

Four same-scene sets show the three variables behind the findings below. Distinct tonal values is our lab metric: how many different sensor values the file actually uses. Render time is the median of three full-size renders on the M5 Pro, including writing the JPEG.

Sony lossless compressed vs uncompressed: same data, smaller file

Within a body, Compressed ran 0.503 to 0.583 of Uncompressed across 12 bodies, right on Sony's "approximately half", and Lossless L ran 0.559 to 0.720 across the eight bodies with all three modes.

Lossless is the only mode whose size depends on the scene. Uncompressed stores a fixed 16.0 bits per sensor pixel and old-style Compressed a fixed 8.0 (all 14 and all 17 of our files, to the decimal), so those files are the same size whatever you point the camera at. Lossless L ranged from 8.72 to 11.37 bits per pixel across 11 files from 10 bodies, median 9.68, because how well the data packs depends on how much fine detail and noise the scene has. On a low-detail scene it gets close to Compressed: the a1 II's Lossless L file, that overcast sky, is 57.91 MB versus 53.44 for Compressed. On a busy one it doesn't: the a1's is 81.58 compared with 63.22. Card and drive math for Lossless has to use your scenes, not a spec sheet; for photos per card from 32 to 512 GB, see our RAW file size study. (Whole-file sizes also carry the embedded preview JPEG, which is why two files with identical sensor data can differ by tens to a couple of hundred kilobytes.)

Lossless gives the sensor data back intact. Lossless compression is reversible by definition, Sony's guides say the L size "causes no deterioration in image quality", and in the same-scene table above Lossless L stored about as many distinct tonal values as Uncompressed (within 3%) on every set (a7R V: 14,636 versus 14,148). We didn't compare a lossless and an uncompressed frame of the same exposure pixel by pixel, so read this as the tonal range being intact, not as a pixel-level proof.

Render time is the one cost we measured. In all eight bodies with all three modes, the lossless file took longest to render at full size and the uncompressed file was quickest, with Compressed in between; the a7R V's 1.50, 1.19 and 0.92 seconds in the table are typical. Unpacking costs work, the difference is a fraction of a second per frame, and it's one of two things Uncompressed still wins, the other being software old enough to predate Sony lossless.

Is Sony compressed RAW really 14-bit? It keeps about 2,000 tonal steps

Compressed files use a 14-bit scale but keep at most about 2,000 steps on it. Of our 17 older Compressed files, 14 carry a 14-bit tag and three a 12-bit one (an a7R IV, an a7 III and an a7 II file); Sony's file-type tag for Compressed carries no bit label at all, only the Uncompressed tag says "14-bit". Either way the stored values sit on a 14-bit scale, and the count of distinct values never passed 2,029, which is about what an 11-bit curve allows (2,048 codes). The same-scene table shows the gap: a7R V 1,778 versus 14,636 lossless, a1 2,029 versus 16,358, a1 II 1,151 versus 3,393 on that flat sky. In the brighter half of each file's values the stored numbers step in gaps of 8 to 32, where lossless and uncompressed files step by 1 or 2. The counts vary with scene and exposure, which is why the same-scene pairs matter more than any single number.

Why is in a RawDigger teardown from March 2014. First a tone curve squeezes the 14-bit values into 11 bits, which is where most of the missing steps go. Then each row is cut into 32-pixel blocks, and each block stores its brightest and darkest value in full plus the other pixels as small 7-bit steps between those two. When a block's range is small, the steps are fine. When it holds both a bright edge and a dark background, the steps get coarse and the block may posterize, and that is where the artifacts live.

They've been photographed for years. diglloyd showed them in February 2014 as 32-pixel-long lines surrounding two bright star trails on a reader's Sony a7 frame. Stephen Bay's real-world examples (August 2019, updated November 2020) add a cityscape after sunset, fireworks and, from an a7R IV, the moon. DPReview's 2015 analysis puts them at high-contrast edges, says they get worse when you brighten the file, and adds the line every forum quotes: the impact "isn't often visually significant". Both are true, because most frames never show it and the ones that do are the ones you push hardest.

12-bit vs 14-bit Sony RAW: the 12-bit file saves nothing

There is no 12-bit setting to pick, and when the camera drops to 12-bit on its own the file doesn't shrink. Sony's RAW File Type pages don't say when that happens; AlphaShooters' a7 IV test (December 2021, updated June 2022) reports Compressed as 12-bit in continuous drive and DPReview's a7 IV review lists the same, other testers report other depths for other bodies, and we didn't test burst files, so treat it as a report, not a spec. The size, though, is settled by the formats themselves: Uncompressed always stores 16 bits per pixel and old-style Compressed always 8, whatever the camera fed them. Our set had two pairs of files that differ only in bit depth, a7R IV Uncompressed at 12 and 14 bits and a7 III Compressed at 12 and 14 bits, and the sensor-data blocks are the same size to the byte: 122,419,200 bytes for both a7R IV files, 24,337,152 for both a7 III files. The 12-bit Uncompressed file uses only every fourth tonal value inside the same 14-bit box, and its own label still says "Sony Uncompressed 14-bit RAW".

Sony Lossless M and S aren't real RAW files

Thirteen of the 14 Sony Lossless M and S files we measured store processed color pixels, not sensor data. The camera has already turned the sensor data into finished color pixels, applied white balance and shrunk them (the file's own metadata says three channels at 15 bits each in a luminance-plus-color layout, the arrangement JPEGs use, with color sampled more coarsely in M than in S). That covers 12 full-frame files from six bodies plus the a7 IV's APS-C S. What you get is an editable, high-bit-depth, losslessly packed image at a lower resolution, and the tools that need sensor data can't use it. Lightroom's Denoise declines M and S files for that reason, per community reports on Adobe's forum (October 2023, community experts, not an Adobe statement). darktable's camera-support page lists ARW 4.0 and 5.0 "downsized lossless" files as explicitly not supported. The open-source RAW reader many editors share added them in January 2026 under the name "pseudo-RAW".

S isn't even efficient. Per output megapixel, Lossless S cost 2.10 to 2.81 MB versus 2.04 to 2.28 for Uncompressed L, more than the same body's Uncompressed on all seven S files; an a7R V Lossless S file is 42.36 MB for 15 megapixels, its Uncompressed L 134.7 MB for 61. M does better, 1.53 to 2.32 MB per megapixel, cheaper per pixel than Uncompressed L on four of six bodies, but it's still processed pixels. If you want a smaller full-resolution file, that's what Lossless L is for. If you want fewer pixels, shoot L and downsize on the Mac.

One exception, and it's an odd one: the a7 IV in APS-C crop. There, "M" is just the crop's own pixel count, and the file is still sensor data at 14 bits. The 12 processed-pixel files the Mac opened rendered at their reduced M or S size, as expected.

The a7 V and a7R VI: Compressed (HQ), and no Uncompressed

The a7 V's RAW File Type menu has three options and none of them is Uncompressed: Lossless Compressed, Compressed (HQ) and Compressed, with no M or S, per Sony's guide, in a new file version, ARW 6.0, per its spec page. The a7R VI's guide lists the same three. Our a7 V files add two facts.

First, Compressed (HQ) is not bigger than Compressed. On the same scene a minute apart, the a7 V's full-frame HQ file is 23.23 MB and its Compressed file 23.31; in APS-C crop, 11.48 versus 12.10. The only thing inside the file that marks HQ as different is a quality flag; both carry the same internal format name and the same ARW 6.0 version, and both sit at about 0.52 to 0.54 of the Lossless L file from the same scene. So HQ is not a size decision, and Sony's guide is the only public word on what it buys you.

Second, the a7 V's Compressed is a new format, not the old one at a new size. The old Compressed was a fixed 8.0 bits per pixel; the a7 V's Compressed and HQ files came out at 4.47 to 4.96 bits per pixel, and variable, with the two crop files at different rates than the two full-frame ones. Per output megapixel the full-frame file is 0.71 MB, against 1.03 to 1.34 for full-frame Compressed on every other body in the table. We couldn't count its tonal steps: no reader we had opens ARW 6.0 Compressed except the Mac's own.

Put those next to Sony's buffer table and the a7 V verdict writes itself, with one hedge. HQ gets Lossless's small buffer (about 170 frames, mechanical shutter) while its files are Compressed-sized. So: Lossless for quality, Compressed for bursts, and HQ only to save card space against Lossless, if you trust Sony's "higher image quality" without a definition. Sony doesn't say what HQ changes, and we haven't measured an a7R VI file.

Burst rate and buffer: where Compressed still wins

Lossless costs nothing in quality and something in speed, and Sony's guides put numbers on it per body. Every figure below is from the continuous-shooting page of the body's help guide unless the source column says otherwise; Sony gives buffer counts as approximate and for a specific card (a CFexpress Type A where it names one), so treat them as relative.

Read those against the file sizes and a pattern shows. On the a1, a1 II, a7R V and a7C II, Uncompressed has a smaller buffer than Lossless and a bigger file; only the a7 IV gives the two the same speed and the same buffer, and the a1 and a1 II share only the 20 fps cap. That is why Sony could drop it on the a7 V and a7R VI without anyone losing a picture. Our a7 IV, a7R V and a6700 editing guides cover the rest of those bodies.

What your Mac opens: 59 of 60 Sony RAW files on macOS 27

All 14 bodies are on Apple's macOS 27 camera list, dated September 22, 2026, and all 14 show up in this Mac's own Raw Support list. Of the 60 files, 59 opened at full size with the Mac's built-in RAW support, run from Terminal through the pipeline Finder, Quick Look, Preview and Photos share: every Uncompressed, Compressed, Compressed (HQ) and Lossless L file, and 13 of the 14 M and S files.

Not everything matched the list. Apple footnotes exactly one Sony body, the a7 V, as "Lossless compressed format only"; our four a7 V Compressed and Compressed (HQ) files, full-frame and APS-C, all opened at full size as real renders, not the embedded JPEG. And the one file that failed carries no footnote at all: the RX1R III's Lossless M returned "Cannot extract image from file" on all three runs, while the same camera's L and S files opened. If an RX1R III M file shows a blank thumbnail on your Mac, that's why; the general checklist is in why a RAW file won't open on your Mac, and the ARW-specific walkthrough in how to open ARW files on a Mac.

Preview, Photos and Quick Look use that same support underneath, but we didn't run each of them on the 60 files, so a difference in one of those apps is possible and untested. To check any file's own mode without installing anything, drop it into our free in-browser EXIF viewer: the RAW file type and quality fields are the ones to look at, and nothing is uploaded.

Which editors open which Sony RAW mode

Support for the older modes is settled; the a7 V's formats and the M/S files are where editors differ. Cells are what each maker's own documentation or forum says, with the date. Blank cells mean we found no dated statement either way; the first row's modes have opened in mainstream editors for years.

Sources: Adobe's Lightroom Classic 15.2.1 announcement (March 18, 2026); Capture One support note (2026, snippet only); DxO forum thread (user reports; no DxO staff posted in it); darktable camera support; RawTherapee issue 7570. If you rely on DxO, darktable or RawTherapee and own an a7 V, the matrix decides the setting for you.

Which Sony RAW file type should you shoot?

Lossless Compressed L wherever the body has it, Compressed when the burst matters more than the file, Uncompressed only on bodies with no lossless option or for software that predates it. The table says where the lines fall per body; Lossless M and S are off the list everywhere, for the reasons above.

Uncompressed buys nothing in quality where Lossless exists, and costs space, roughly 1.4 to 1.8 times the file, plus buffer on every lossless body we have figures for except the a7 IV. Its two remaining uses are software that predates Sony lossless (darktable added it in mid-2023, and Adobe reportedly needed a 2021 release) and the faster render we measured, which adds up if you cull thousands of frames on an older Mac. Sony has already removed it from the a7 V and a7R VI. Our a7 III guide covers that body's editing options, and if you're still deciding whether to shoot RAW at all on a Sony, RAW vs JPEG on Sony Alpha is the step before this one.

FAQ

Is Sony lossless compressed RAW the same quality as uncompressed?

Yes. Lossless compression is reversible by design, Sony's guides say the L size causes "no deterioration in image quality", and on the same scene our Lossless L files stored about as many distinct tonal values as Uncompressed (within 3%) (a7R V: 14,636 versus 14,148). Lossless L ran 0.56 to 0.72 of the Uncompressed size across eight bodies. The measured cost is render time: lossless files opened slowest on our Mac in all eight bodies with all three modes.

Are Sony compressed RAW files 12-bit or 14-bit?

The values sit on a 14-bit scale, but Compressed keeps far fewer steps inside it: at most 2,029 distinct values in our 17 older Compressed files, versus 14,636 (Lossless) and 14,148 (Uncompressed) on the same a7R V scene. Fourteen of those files are tagged 14-bit and three 12-bit; the camera decides that, and the 12-bit file is no smaller. A 2014 RawDigger teardown explains the loss: a tone curve to 11 bits, then 32-pixel blocks with 7-bit steps.

Does Sony compressed RAW reduce dynamic range?

Slightly, in the shadows, per DPReview; the black-to-white scale is unchanged. Compressed files span the same 14-bit range as Uncompressed but keep far fewer steps inside it, mostly through a tone curve to 11 bits. DPReview's 2015 analysis says "the compression curve throws away more shadow data than would be ideal: reducing dynamic range". In practice that shows as posterization and edge artifacts after big shadow pushes, and rarely otherwise.

Are Sony Lossless M and S real RAW files?

Not in the usual sense. Thirteen of the 14 Lossless M and S files we measured store finished color pixels, not sensor data. S costs more per pixel than Uncompressed L (2.10 to 2.81 MB per megapixel versus 2.04 to 2.28); M is often cheaper. Lightroom's Denoise declines them because it needs sensor data (community reports, not an Adobe statement), and darktable lists them as explicitly unsupported. The a7 IV's APS-C M file is the exception: still sensor data.

Why does my Sony a7 IV only shoot 6 fps?

Because the RAW file type is set to Uncompressed or Lossless Compressed. Sony's a7 IV guide says continuous shooting slows with either; AlphaShooters measured 6 fps versus 10 with Compressed (December 2021), and DPReview's review agrees. The a1 and a1 II cap at 20 fps instead of 30, and the a7R VI at 15 instead of 20 with the electronic shutter. The a7 V loses no speed, only buffer: about 170 frames instead of 1,000 or more.

Why won't Lightroom, DxO or Capture One open my a7 V RAW files?

The a7 V writes a new file version, ARW 6.0, and its Compressed and Compressed (HQ) modes needed new support. Adobe added them in Camera Raw 18.2.2 (March 12, 2026) and Lightroom Classic 15.2.1 (March 18, 2026). Users on DxO's forum report PureRAW 6.0.1 still refuses them, and Capture One's support note reportedly allows Lossless only. Shoot Lossless until your editor catches up; macOS 27.0 itself opened all four of our a7 V Compressed and HQ files.

Editing any of these on a Mac

The lab above tested macOS itself, not RevelRaw, so here is what we can say about our own editor without stretching it. RevelRaw opens a RAW with the Mac's built-in RAW support first, and when the Mac declines a file it falls back to its own second reader; the choice is made by the outcome, not by which mode you shot. In our own test run over the whole raw.pixls.us archive, it read 1,931 of 1,940 files, and the nine it couldn't were not Sony files. From there, AI scene detection ranks 40+ curated presets for the photograph, you fine-tune and export, and nothing leaves your Mac. Everything else about the ARW format and editing Sony RAW on a Mac lives on those two pages.

Related reading: What is an ARW file? · How to open ARW files on a Mac · Free sample RAW files (CC0)