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Raw files

Page history last edited by GregReser 14 years, 7 months ago

from Adobe XMP SDK http://www.adobe.com/devnet/xmp/pdfs/XMPSpecificationPart3.pdf


Camera raw formats

Many raw formats look like TIFF, but do not behave as expected in various ways. Do not attempt to process

camera raw files with generic TIFF software. Similarly, you should not pass a raw-format file directly to XMP

Toolkit file handlers (XMPFiles), but should use the Adobe Camera Raw (ACR) SDK instead.

When writing your own metadata handler for camera raw files, it can be difficult to distinguish a possible

camera raw file from a generic TIFF file. A pragmatic partial solution is to filter by file extension. Known

camera raw extensions include:

GIF (Graphic Interchange Format)

In a GIF 89a file, an XMP packet is in an Application Extension (see the following figure). Its Application

Identifier is 'XMP Data' and the Application Authenticator is 'XMP'. The Application Data consists of the





From Aperture User Network - David Schloss http://www.apertureprofessional.com/showthread.php?t=837


What I'd like to do is keep my RAW masters in their existing places, open & work on them in Aperture, export the TIffs , or whatever, with metadata embedded and then,export the metadata as xmp sidecars to be stored with the RAW masters on the external drives where they are archived. I can't figure out what to do with metadata text.


"There's no real reason to export a tiff file plus an XMP sidecar. The XMP sidecar file exists due to the limitations of the raw "format" whcih isn't really a format so much as a dump of data off the sensor. Since raw files weren't designed to be end-product files, they don't have a standardized place to put the IPTC data.

TIFF and JPEG do have places for this and so when you export a file in this type, the information is written to the file automatically. No reason for the sidecar file then.

You can also, if you need for some file trafficking purpose, export just the metadata. (File>Export>metadata) which will generate a txt file containing data for all the exported files."


Lightbox XMP that's now available. According to Josh, it provides 3 main benefits. "The first is that by exporting XMP sidecar files for referenced masters, it becomes possible for information you entered in Aperture to be visible in another program, like Adobe Bridge. Secondly, by allowing the user to embed a complete set of XMP metadata into a file, your exported images contain more information, in a standard format, than the build-in export tools provide. Lastly, by allowing the user to export XMP sidecar files with exported images (or just to just export the sidecar files), Lightbox XMP allows the user to access the metadata from Aperture in an open-standards-compliant format." So while it may not be for everyone, if you find that you have a need to export xmp sidecars, check out (www.lightboxsoftware.com/aperture/




DNG (Digital Negative)

DNG is a publicly documented, standardized format created by Adobe for storage of raw image data as

captured by digital cameras. It was created as an alternative to the more than 400 wildly varying formats

all called "camera raw;" see “Camera raw formats” on page 16.

DNG files can embed XMP metadata; they are, in fact, well-behaved TIFF. They can be processed by the

Adobe DNG SDK, by the Adobe Camera Raw (ACR) SDK, or by the TIFF handler in the XMP Toolkit. The

primary difference between the Adobe DNG/ACR handlers and the XMP Toolkit TIFF handler is that the

TIFF handler does not interpret the Exif MakerNote tag.

Metadata can be embedded in DNG in the following ways:

➤ Using TIFF or Exif metadata tags

➤ Using the IPTC metadata tag (33723)

➤ Using the XMP metadata tag (700)

Note that TIFF and Exif use nearly the same metadata tag set, but TIFF stores the tags in IFD 0, while Exif

store the tags in a separate IFD. Either location is allowed by DNG, but the Exif location is preferred. See

“TIFF and Exif tags for metadata” on page 73.

Reference For further information on this file format, see:


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