What information is lost when converting a RAW file to 16-bit TIFF?
Asked 2/26/2019
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RAW files can store extensive shooting information such as ISO, lens data, and sometimes additional camera-specific metadata. If I convert a Canon CR2 RAW file to a 16-bit lossless TIFF in Photoshop CS6, what information or editability will I lose compared with keeping the original RAW?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
7y ago
2 Answers
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Well, first, the image will be demosaiced, white and black levels set, white balance adjusted, and a tone curve applied. With 16 bits to play with, most of this can be adjusted later without much problem — but it is lossy. The demosaicing is irreversible. None of this is metadata, but it is important to know. See more at What is lost when RAW is exported to TIFF for editing? and Does converting RAW files to TIFF lose image quality?
Second, there is information stored in something called "maker notes". This often holds things like focus point selected, face detection information, and other non-standard metadata. Sometimes this is even encrypted. Some programs will ignore this completely and so not copy it to your new file — in particular, Adobe tools like Photoshop and Lightroom apparently drop makernotes.
The best source of info I know for manufacturer-specific details is the exiv2 metadata library documentation.
Originally by user1943. Source · Licensed CC BY-SA 4.0
user1943
7y ago
0
Generated from our catalog & community — verify before relying on it.
The main loss is not ordinary EXIF like ISO or lens info, but the RAW sensor data and some camera-specific metadata.
When you convert RAW to TIFF, the image is rendered: the Bayer data is demosaiced, black/white levels are set, white balance is applied, and a tone curve is applied. A 16-bit TIFF preserves a lot of quality for further editing, but this rendering step is still lossy because you can no longer go back to the original undecoded sensor data.
What may also be lost is maker-note metadata: proprietary camera information such as selected focus point, face-detection data, and other manufacturer-specific fields. Some software may ignore or fail to copy these maker notes into the TIFF.
So in practice:
- Standard metadata may remain.
- RAW processing flexibility is reduced.
- Demosaicing is irreversible.
- Some proprietary camera metadata may be lost.
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