More and more photo inkjet papers are being touted as ‘fade-resistant’ and ‘archival-safe’, but experts say these marketing pitches don't always provide good information on how long it will take for skin tones to turn green and paper to yellow on precious family photos.

Because there's no standard for measuring inkjet print longevity, it's difficult for consumers to make comparisons of photo papers. Consequently, experts say, people may find that some photos expected to last for decades will start to fade after just a few years.

The latest salvo in the longstanding debate has come from HP and Epson. The companies have dismissed claims by third-party paper vendors such as International Paper, Kodak and Staples that their paper will produce archival-quality prints on any inkjet printer.

Specifically, Epson and HP strongly dispute Kodak's claim that prints made on their printers with Kodak's special paper will last 120 years before fading. Similarly, the printer vendors dispute International Paper's claims that prints made on the company's recently introduced National Geographic Premium Paper High Gloss will last "more than 100 years”.

At the heart of the inkjet photo paper debate are conflicting opinions on how best to test printed photographs in order to project how long an image will last before it begins to fade.

For years, under the auspices of the International Standards Organisation (ISO), printer makers and third-party providers of digital imaging products have been trying to settle on a mutually agreeable way to predict image longevity. But with no standard in sight, Wilhelm Imaging Research, an independent research laboratory, earlier this year announced that it would begin certifying digital imaging products for print longevity in order to assist consumers in making buying decisions.

WIR has tested Kodak and Staples papers, and its print longevity projections for those products fall far short of those achieved by HP and Epson papers. For example, WIR projects that images printed with Kodak photo paper using HP Photosmart 145 and 245 printers will last only 11 years, 109 fewer than Kodak is claiming.

All labs, including WIR, project image longevity based on tests involving exposure to light, heat, humidity and air pollution. And all labs use a procedure called accelerated fading to test for resistance to light exposure. Basically, accelerated fading involves exposing images to intense light and using mathematical formulas to project when the picture might degrade to an unacceptable level.

But WIR and others don't see eye-to-eye on how to test for light fading. Kodak and Staples say WIR's methodology places too much weight on fading due to exposure to light. They argue that WIR doesn't sufficiently factor in the importance of an image's resistance to heat, humidity and ozone pollutants.

WIR counters that Kodak's tests aren't sufficiently stringent, and that Staples has provided no scientific data to back up its claim that its photo paper is ‘fade-resistant’. In general, WIR says, consumers should be wary of vendor claims that aren't explained in detail or supported by independent testing.

Ultimately, the best way to extend the life of your images is to keep them in a photo album or even a shoe box. Displayed on walls, images are affected by light and air pollutants. And it's best to keep digital copies of pictures on a CD or DVD.

"Consumers can't put all the responsibility of preserving images on the photo paper," says Dan Burge, a scientist with the Image Permanence Institute.

"It's up to the consumer to take good care of their images if they want them to last," he says.