Author Topic: Offset of the tagnames in Nikon raw photos (nef)  (Read 746 times)

Martin63

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Offset of the tagnames in Nikon raw photos (nef)
« on: November 23, 2017, 02:09:25 PM »
Hello again,

after playing around with the commandline options of the Exiftool, and analyzing dozens of nef-files, I've noticed that the embedded jpg in my nef-files, made by MY camera, always starts at offset 42272 (0xA520). Nef's made by other Nikons start on a different offset. What I'd like to know is: the tagname for 42272 is "Preview Image Start".
My question: is there a way to let Exiftool.exe display the tagname AND the offset (hex) of that tagname, so, in my case, something like:

0xABCD Preview Image Start: 42272, where 0xABCD represents the offset of this tagname
(character "P" in Preview...)
0xBCDE Preview Image Size: 161234   
I need the offset of the tagname in my program, written in Lazarus. I know, I already call Exiftool.exe to retrieve number of tags, but I want the NEF being viewed on a form and the imagecomponent only supports jpg. Extracting the jpg with -b to a tmp-file and display the tmpfile takes too much time.
A search to (A520) in an hex-editor doesn't give the desired result.

I'm almost sure Exiftool has a buildin option for this, but I can't find it.

Best regards,
Martin

Phil Harvey

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Re: Offset of the tagnames in Nikon raw photos (nef)
« Reply #1 on: November 23, 2017, 02:59:52 PM »
Hi Martin,

I don't know what you mean by the offset of the tag name, but perhaps it is the offset of the tag value in the file?  If so, you can use the -v3 option to see this (along with probably a lot of other stuff you don't care about).

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).

Martin63

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Re: Offset of the tagnames in Nikon raw photos (nef)
« Reply #2 on: November 24, 2017, 02:49:35 AM »
Hi Martin,

I don't know what you mean by the offset of the tag name, but perhaps it is the offset of the tag value in the file?  If so, you can use the -v3 option to see this (along with probably a lot of other stuff you don't care about).

- Phil

Phil,

you're right, I meant the offset of the tag value. And -v3 gave the answer.
Thanks a lot.

Best regards,
Martin