Assignment 3: Revisited - Metadata

This is the first of a couple of posts to follow up on the tutor feedback for assignment 3, this one just for metadata (data about data) as it is potentially a large subject to cover.

The tutor comment was "the absence of metadata should be attended to before submission for assessment". I think this is because I don't always write out the metadata in the assignment notes document I provide to the tutor but in fact the selected metadata is always available via this on-line log. And so this post is to explain a little of the metadata processing that goes on in my current workflow, how to access that data and to highlight some potential metadata deficiencies.

First up it seems worth defining a couple of terms:

• XMP or Extensible Metadata Platform which is Adobe's standard for processing and storing standardized and proprietary information
• EXIF or Exchangeable image file format data which can be thought of as the technical data relating to the exposure, camera settings and lens
• IPTC or International Press Telecommunications Council data which can be thought of as commercial and descriptive data

The process starts with a digital camera body (Canon) which records metadata along with image data and in my case this is normally stored as a raw file (.CR2). The camera records EXIF data and in the case of Canon some limited IPTC data such as Author and Copyright text which can be set using the Canon EOS Utility software. The image files are then transferred to a PC (I use the LR Import to do this) and at this stage only a very limited amount can be done with the raw files based on what the operating system can do (I use Windows 7, 64 bit), for example thumbnails and previews can be seen if the appropriate RAW codec has been installed and some basic properties can be viewed, though Canon do not fully support 64 bit operating systems at this point in time!

If such a raw file is opened in Photoshop then the File Info looks something like this:

Lightroom reveals some extra data such as exposure compensation, subject distance etc:

And holds the IPTC data, some of which has been added as part of the import processing (and which can be written to xmp sidecar files if required for subsequent processing in other applications):

When exporting a developed image from LR, by not ticking the "Minimize Embedded Metadata" option the metedata is written out to the jpeg file. All my exercise and assignment photographs are made available through the blog by being published to Picasa and Picasa then allows some of the metadata to be viewed for each image, by clicking the "more info" link under Photo Information, for example:

Here's an image link so you can try it:

From Bo'ness

So what are the deficiencies with this metadata approach?

Some data is not recorded:

• Use of filters (e.g. ND grads, polarisers etc)
• Use of Extensions tubes (strictly speaking not actual lenses)

Some data is partially recorded:

• Off camera flash (OCF) firing will not be recorded if it was triggered by a sync cable or similar 'dumb' method. However it will record if attached with a TTL cable or with the PocketWizard Min/Flex radio triggers.
• Coordinates can be recorded by a GPS unit (Geotagging) and the GPS data merged later with the image metadata, typically by matching timestamps. Read more on Capturing GPS data for photo locations.

Some data is on the camera but does not appear later:

• Flash Exposure Compensation (FEC).
• Focus point selection (which can be shown as a red dot on the camera display panel).

Historic data

Having all this metadata does allow for some historic analysis, using something like Lightroom and a spreadsheet application makes for some easy graphical interpretation. For example here is some analysis performed on my 2009 metadata.