Street Photography Magazine

(supported by the IPTC committee itself) for

replacing it with XMP. However, such a

change would only affect the format and not

the definition of the IPTC data fields.

The original 1990 IPTC-IIM (Information

Interchange Model) standard, which has been

updated several times since it was introduced,

has now been replaced with the newer

IPTC-NAA (Newspaper Association of

America) standard, which is divided into

‘Core’ and ‘Extension’ data field sets. The

Core fields cover most currently relevant

data, while the Extension set covers more

comprehensive information to describe

content, aid administration and define

licensing and copyright terms. If you want

to ensure backward compatibility for your

images, you should definitely stick to

using the Core data set. Not all applications

are capable of displaying Extension data

fields.

XMP – Snapping at IPTC’s

Heels Since 2004

Like IPTC, the XMP (Extensible Metadata

Platform) format is eminently suitable for

defining keywords for image files. XMP is

generally considered to be more up-to-date

than IPTC (see below). Although the data

fields themselves are largely the same, the

format in which the data is saved is very

different.

XMP data can be written directly to an

image file – as is the case with DNG, TIFF, PSD

and JPEG files in Lightroom –whereas the lack

of standardized RAW image formats makes it

prudent to save RAW metadata to a separate

(.xmp) sidecar file with the same name as the

image file.

Lightroomuses sidecar files to store not

only basic IPTC and Exif image data, but also

the details of any adjustments you make using

the program’s image processing tools. You

can also edit XMP data to include extra

information (such as geodata) that can be

added later.

There are disadvantages to using XMP

sidecar files, especially if either the image or

metadata file gets unintentionally renamed or

moved within the host file system. It is always

safer to manage your images via the

program’s interface.

Sidecar files also have their advantages.

First and foremost, they enable you to work

around the limitations of the countless

proprietary RAW file formats available today.

For example, if you want to add GPS data to a

Nikon NEF file, you can’t even use Nikon’s own

Capture NX 2, whereas an XMP sidecar file and

GeoSetter do the job admirably. And

remember: if you use sidecar files, you can

only ever access your photos in read mode,

which is the best possible way to prevent

damage to the original image data.

Adobe is the driving force behind the XMP

format, and provides a free SDK along with

the original format specifications for anyone

who wants to develop their own ‘smart

assets’. XMP has been around since 2001, and

has been the suggested successor for the

established IPTC standard since 2004.

However, in spite of Adobe’s enormous

market presence and an explicit

recommendation from the IPTC itself, the

changeover still hasn’t fully taken place.

We are convinced that XMP has a bright

future as a universal container format for

many types of metadata, particularly as it has

Image Database Software | Metadata

Rating flags or stars and color codes are

a great aid to sorting images but, because

every program has its own system, they are

not of much practical use as permanent

archiving tools

Rating systems that use stars or color codes are very helpful when

it comes to pre-sorting collections of digital images. The IPTC

metadata standard has no provision for these types of data fields,

whereas XMP includes the ‘xmp:Rating’ field that specifies

star-based ratings.

However, software manufacturers still tend to prefer to do things

their own way. Picasagives us the options of a single star and no

colors at all, while Capture NX 2offers up to five stars and nine

colors, Windows Explorer has up to five stars but no colors, and

Lightroom compounds the confusion with its five stars and five

different color codes. This means that each system is only of use

within its host program, but lacks the necessary interoperability

for use with other software.

Even apparently identical functions are often good for a surprise. For

example, if you add star ratings to a single NEF file using View NX2

and Lightroom, the metadata produced by each program cannot be

interpreted by the other – Nikon saves stars directly to the image

data, while Lightroomsaves them in an XMP sidecar file.

Sorting Images using Stars and Color Codes