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When I attempt to rotate a CR2 file in Photo Viewer, a message appears:

That didn't work, RAW files don't rotate. Select edit to rotate and save it as a different file type.

There are many tips to rotate a raw file (not just simply save it in a different file type), e.g. using an exif tool. Apparently it can be rotated. However, I wonder why it shouldn't be rotated at the first place.

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  • \$\begingroup\$ What specific "Photo Viewer" are you using? \$\endgroup\$
    – Michael C
    Commented Apr 7, 2021 at 11:26
  • \$\begingroup\$ the native Photo Viewer of Windows 10 \$\endgroup\$
    – Ooker
    Commented Apr 7, 2021 at 15:35
  • \$\begingroup\$ Would that be the old classic one actually labeled "Windows Photo Viewer" that you only have in Win 10 if you upgraded from Win7 or Win8 (Vista) to W10, or the new one labeled "Photos" that you have if you either did a clean install with Win10 or if you upgraded? (LOL - I don't know if it really makes much difference in this context, but the two are totally different applications with totally different interfaces, so it wouldn't surprise me if they were also radically different under the hood.) \$\endgroup\$
    – Michael C
    Commented Apr 8, 2021 at 10:05
  • \$\begingroup\$ Based on your screenshot, I'm pretty sure that is the Windows 10 "Photos" app, not the older "Windows Photo Viewer" that came with earlier versions of Windows \$\endgroup\$
    – Michael C
    Commented Apr 8, 2021 at 10:07
  • \$\begingroup\$ @MichaelC yes sorry, the newer "Photos" app \$\endgroup\$
    – Ooker
    Commented Apr 9, 2021 at 6:13

2 Answers 2

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You can't actually rotate any file. You only can rotate images, then save those images to a file.

But it is usually not possible to write (in the sense of changing the sensor data) RAW files; it would be possible theoretically, of course (your camera does it), but no software i'm aware of does it, not even the proprietary ones of the camera manufacturers.

What might be possible, with tools like exiftool, is to change some of the other data (aka metadata) contained in the file, like the thumbnail or EXIF fields, and set the flag in the EXIF data which indicates camera orientation to rendering software. Usually this isn't terribly useful since RAW files aren't practical for direct viewing anyway, you typically open them in some image conversion software and save them eg. as JPEG. Or you apply all edits you like "virtually" in software like Lightroom which applies those edits on the fly when viewing the image.

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  • \$\begingroup\$ It's very useful for most raw processing applications to allow a file to be appended with rotation instructions. The next time one opens the same file with the same app, the image is displayed with the instruction applied. And for what it's worth, if I rotate a raw file in Canon's DPP 4, when I open the folder containing that file and windows shows a thumbnail for that image it is also rotated the way I set it with DPP, rather than the way it was set by the camera. So the instruction doesn't have to be proprietary for a specific app. \$\endgroup\$
    – Michael C
    Commented Apr 7, 2021 at 11:30
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    \$\begingroup\$ Yes, like i said it's possible to edit metadata. and of course DPP doesn't have any qualms writing CR2's, other applications typically refrain from doing so as it might destroy the undokumented maker notes. \$\endgroup\$
    – ths
    Commented Apr 7, 2021 at 12:24
  • \$\begingroup\$ There's a difference between "writing .CR2s" - your computer does that every time you copy a .CR2 - and altering the sensor data that is but one section of the many sections of information contained in a raw file. DPP does not, to the best of my knowledge, ever alter any actual sensor data in .CR2 files. But it does alter data in the instruction set regarding how that sensor data should be interpreted, as does any other raw processing program that allows one to save the raw processing instructions within the raw file itself, rather than only in a sidecar file. \$\endgroup\$
    – Michael C
    Commented Apr 7, 2021 at 13:28
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    \$\begingroup\$ because they are raw - ie. the sensor data of the camera which needs to be interpreted by software (and there is no definitive "correct" interpretation) to display. if you want to edit an image, it just makes more sense to save it to a different format like jpeg or tiff which does have a definitive representation. also, raw formats are usually not officialy disclosed by manufacturers. meta data is a diffent thing and can be changed without affecting the stored pixel data. \$\endgroup\$
    – ths
    Commented Apr 7, 2021 at 17:40
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    \$\begingroup\$ @Ooker See this question for more than you ever wanted to know about raw files: What does an unprocessed RAW file look like? \$\endgroup\$
    – scottbb ♦
    Commented Apr 7, 2021 at 21:54
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RAW image files aren't meant to be manipulated directly. If your photo viewer is viewing a raw image file, it is probably looking at the JPEG thumbnail embedded in the raw file. The photo viewer I use, JPEGview, allows you to view the embedded thumbnail in raw files and allows you to rotate the view. However, you can't save the rotation info in the raw file with JPEGview, however, it will allow you to save the edited thumbnail as a separate JPG image file.

Programs that are used to edit raw images don't manipulate the raw file directly. Instead, a script of your changes are recorded. That script is played back when you convert raw format to something viewable like JPEG or TIFF. Programs like Lightroom show a list of the edits you have made which is essentially the script.

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