Street Photography Magazine

Product photos in online shops can be
protected using invisible watermarks,
although visible watermarks are still more
common for this type of application as they
are easier to apply. Online shops don’t usually
rely on the aesthetics of a product photo to
make a sale anyway.

Analog Reproduction

Watermarks also have their uses when it
comes to preventing analog (i.e., print)
reproduction of high-resolution digital images
downloaded from the Internet. In the past,
people tended to use only low-resolution
images in online situations, but the trend is
moving quickly toward higher online
resolutions. The thumbnails that used to be
popular look unimpressive, even on today’s
handheld devices. You need images with
at least three megapixels of resolution if
you want them to look good on the
2048 x1536-pixel screen built into the current
model iPad. Commercial websites are sure to
follow this trend, thus increasing the risk of
analog reproduction of digital image data.

Conclusion

Digital watermarks are the only way to reliably
embed copyright information in an image
without altering it visually, and they also make
it possible to locate stolen photos. Previous
attempts at creating robust watermarks
proved too easy to crack, and the last test
performed by our German sister magazine in
2009 showed that all it took to deactivate
most watermarks was to rotate an image by
one degree. The tests documented on the
following pages take a close look at the latest
watermarking developments. The Chroma
digital watermarking technology introduced
by Digimarc in 2010 claims to be more robust
and less conspicuous than any of its
predecessors’ methods. Read on and find out
for yourself what’s good and what’s not.

Invisible Watermarks | Overview

Digital watermarks are similar to

steganographic techniques in that they

embed additional information in digital

image files. In fact, some of the techniques

used to create digital watermarks directly

involve steganography. Steganography

hides invisible information in a carrier

medium in such a way that it can only be

read by the intended recipient. This can,

for example, be a text string hidden in an

image. The image remains the same

visually while the additional information

remains hidden. The main aim of the

steganographic process is to hide

information, whereas invisibility is only the

first degree of protection offered by digital

watermarks. Robust watermarks are

designed to be embedded in the carrier

medium in such a way that the carrier

itself will be destroyed if someone

attempts to remove the watermark

without appropriate authorization. In this

case, it is the irreversible embedding

rather than the hiding of the information

that defines the process. Watermarks are

designed to aid the discovery and

recovery of stolen images, and the

addition of hidden copyright information

is more or less a side effect of the main

process.

Steganography vs. Digital Watermarks

Digimarc watermarks can be read using a Photoshopplug-in or dedicated

Windows client software

The Digimarc online watermark monitoring service is only available

to users who take out a paid subscription