Tagging your images is so cool, compared with using plain old folders…at least that’s what everyone seems to say. But how do your carefully created keywords get attached to your images? What are EXIF, IPTC and XMP? And most of all…why should you care about all of these acronyms? Understanding the different types of image metadata will help you better manage your pictures. Read on to find out what happens behind the scenes of your image tags.
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Why is image metadata cool?
Image metadata in general is defined as “data about data”. In particular, image metadata is information about a specific picture. There are two types of image metadata: technical information about the image and information about the contents of the image. I usually refer to these two types as: technical information and content information. Technical information contains things like: camera type, ISO speed and aperture value. This type of information is created by your camera each time you take a picture. Content information, on the other hand, contains things like: subject, country, category and keywords. Content data is created by you, the photographer, since you’re the only one who can provide content data.
The easiest way to distinguish between different types of image metadata is to think about who needs to create each type. Technical information about an image (EXIF) is created by the camera, while content information (IPTC/XMP) is created by you, the photographer.
What about all these names like: EXIF, IPTC, XMP?
All of these names represent standards for saving technical and content information about images. They are essentially standards for data portions that can be added to image files. While EXIF and IPTC have been designed specifically for image file types (.jpg, .gif, .tiff), XMP data can be embedded in multiple document formats including PDF. Because XMP (developed by Adobe) is newer, it has been developed as a super set (that means that it contains) of IPTC core elements. This means that software usually can save content information in both formats.
Here is an easy way to remember how these names are being used: EXIF is the standard for representing technical information about an image while IPTC and XMP are standards for representing content information about an image. The first is created by the camera while the second by humans.
EXIF contains technical characteristics of the picture
EXIF contains information generated by your digital camera each time you take a picture. It contains technical information about the picture itself like:
- Date picture taken
- ISO speed
- Aperture value
- Exposure
- If the flash fired or not
As you can see, this type of information is generated by your camera and represents all the technical characteristics of your picture. However, it does not contain any information about the contents of your picture. Also, another characteristics of EXIF data is that you are not supposed to modify it. There is software that will allow you to modify EXIF data, but this data is not intended to be modified. It doesn’t really make sense to change it anyway since it is generated by your camera.
IPTC contains information about the contents of the picture
IPTC contains information created by the photographer and entered into the IPTC fields using some software program. The key difference is that the information contained in the IPTC fields represents information about the content of the picture. It is obvious that a camera would have no idea about the subject of the picture, so there is no IPTC metadata in any pictures when you shoot them. Your camera knows nothing about IPTC…and it shouldn’t anyway. Here are some examples of IPTC metadata fields:
- Country
- Subject
- Category – a list of preset categories
- Additional Category – this is free form and you can add text in here
- Keywords – this is where you place your keywords. This is probably the most widely used IPTC field
Again, as you can see, this data is about the content of the picture and you alone as the photographer can enter this data. This is where you need to use software like: Adobe Lightroom, iTag, iMatch, ACDSee Pro and others to manipulate the IPTC information for your pictures. Once you add this information in your software you have to make sure you save it to each image file. Otherwise all this information will stay only in your software.
What’s the point of all this image metadata acronyms?
Again…let’s recap: EXIF contains technical information about a picture while IPTC (and XMP) contains information about the content of a picture. Remember that this information is saved as part of your image file. This means that your image file size will increase…very little though because this information is simple text. The whole point of saving metadata along with each image is to provide information about the image: both technical and content information. So, when your image “travels”, the information about the image “travels” with your image file.
Do you really need to save metadata?
Why would you need them when you can have all this information stored in your software? Well…it’s pretty simple. If you don’t save all this information with each picture, then nobody else but you (using your software) would be able to see this information. If you don’t care about the portability of your metadata (including keywords), then you don’t really care about IPTC (or XMP for that matter). But if you want to pass your pictures to news agencies or most photo sharing websites, you need to do this because they will want to know information about the content of your pictures without having to open and view each picture. This is it on this subject…at least for now.
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I missed this conversation earlier. One of the practical problems with XMP the last I looked is that it it tends to treat all properties as strings. But a whole lot of useful metadata is about objects; an author is not a string Jane Doe but a person that has the name Jane Doe and so forth. This has practical consequences for users and applications. But this all depends on what you need. I raised the issue in an earlier comment in part because I thought Krita has some connection to KOffice. I would think, then, that you might want to look into a common metadata approach and code, API, etc. In that case, XMP would yield problems.I could be wrong in that assumption, though. If the scope of this will only ever be images in Krita, then it might be fine to use XMP.
Ilaria…that’s correct in terms of metadata attributes as being strings. This is the standard that exists. Both XMP and IPTC make all the metadata flat meaning that there is no relationship between keywords in particular. Adobe is trying to insert parent child relationship between the tags saved with Lightroom bit that is not in the XMP or IPTC standards. This is where your folders come in handy because visually you can have relationships between events and categories.
I mostly have .jpeg images in my personal collection but also have a fair amount of photoshop files & MS Office files. I am looking for user friendly D.A.M. software that will save the IPTC/XMP data to the file without subjecting it to another round of .jpeg compression. I would also like to have a captioning/description field and batching capabilities. What software options are there given the above criteria? I would prefer the software to recognize both IPTC & XMP if possible.
Brooke…there are a few options at least. I’m not sure exactly what software doesn’t perform the compression when adding metadata. You can try XnView which is free and has excellent metadata compatibility (both IPTC and XMP).
Another option would be PIE made by PicMeta which is a German program that is very lightweight and has excellent support for IPTC and XMP, but it doesn’t have much else…it’s a fast viewer with great metadata support.
PicMeta is not free, but it’s inexpensive and it will also do batch processing for image metadata…their site is http://www.picmeta.com and look for the PIE product.
Try https://pics.io It is user friendly D.A.M. tool that uses your Google Cloud storage, and you do not pay for the storage. It reads and writes all XMP/IPTC/EXIF and other meta tags and even let you create and save your own meta tags to the files.
Thanks, Vlad. Yah I wanted to add some data to images such as copyright information. Sounds like InfranView can help me with that.
Thanks!!
Mike…yes InfranView will work. Look for the Copyright field in the IPTC fields. This is the field intended for this use.
Check this link out: EXIF Fields.
Glad to hear you found my site helpful.
Are there any programs that will let you easily add cutom metadata to image?
I’m looking for a program that you open, select an image or images. Type in your custom data, and save it.
Thanks for any reply.
Mike
Mike…thanx for your comment. I’m not really sure what you mean by custom metadata. If you mean entering keywords then there are quite a few free programs that would help you to do that. A couple of my favorite free programs are IfranView, XnView and GeoSetter. They would allow you to edit the IPTC metadata that contains keywords.
Hope this helps.