Topics: Developer Forum
Mar 3, 2008 at 5:49 PM
I dumped the info returned from the PhotosGetExif call on a set of images and have a few questions.

1. I happen to notice this for the capture device make tag (Tag = 271), the TagSpace returned says "TIFF" and TagSpaceId is 1. At first I thought that was because the tag, 271, is the same for both EXIF and TIFF. However, I can find another tag where the tag is the same in EXIF and TIF, yet the data returned from the call is TagSpace "EXIF" and TagSpaceId = 0 (3347...capture conditions f number) . So, what's the logic used by Flickr as far as what it gives for TagSpace and TagSpaceId?

2. As far as when the image was taken, I get back 2 different tags (the raw and clean data values are the same for both):

a)Tag = 306, Tag Space = TIFF, Tag Space Id = 1
b)Tag = 36867, Tag Space = EXIF, Tag Space Id = 0

Mind you for (a) there's an EXIF tag with the same number (306) for that correlates to the same piece of data. Likewise, for (b), there's a TIFF tag with the same number (36876) that correlates to the same piece of data. So, I guess I'm curious as to why I didn't see a consistency between the tags in (a) and (b)?


Mar 4, 2008 at 9:28 AM
Edited Mar 4, 2008 at 9:40 AM
I doubt very much whether Flickr has much to do with what is in the actual EXIF data. It usually depends on which camera took the photo and how that camera manufacturer decided to store the information.

Basically the tag space appears to be the 'group' of tags - the TIFF and EXIF are the first two, but others exist, usually manufacturer specific tag spaces.

Looking at one of my photos Tag 306 is the TIFF format's date/time [1].
Tag 36867 is the EXIF date/time [2].

Mar 5, 2008 at 2:07 PM
Tag 36867, for both EXIF and TIFF, is the date/time the original image was taken.
Tag 306, for both EXIF and TIFF, is date/time the image was last modified. Typically those tags will have the same value. For each piece of meta data that I'd like to search for in the hash table returned from the PhotosGetExif call, I'm setting up a table that says look which tag space id and tag id to look for. One way to setup that table would be to just use a bunch of test images to see what I get back from PhotosGetExif call. In liue of that, I was hoping there was some description of what flickr would stick in the hash table for each piece of meta data it comes across in the image a far as tag space id and tag id, as well as which pieces of meta data would even try to pull from the image.
Mar 5, 2008 at 3:03 PM
Flickr doesn't 'put' anything in the EXIF data - it only reads whatever EXIF data is in the image.

What EXIF is stored inside the image file depends on what the software inside your camera, or software you are using on your computer writes into the file. Each piece of software is likely to create its own unique tags, which will be used by no other software, so it would be impossible to create a definitive list of all tags.

Tag Id 306 is in Tag Space "EXIF" and Tag Space Id 0.

Tag Id 36867 is in Tag Space "TIFF" and Tag Space Id 1.

The Tag Id 306 should only appear once in the returned data - if it is returning more than once then let me know the photo id and I'll take a look.