HP has questioned an international standard created to give consumers information on the amount of pages an inkjet cartridge can print.

Compromises by manufacturers and time constrictions have meant important things have been overlooked in elements of the standardisation, HP has said.

The International Organisation for Standardisation (ISO) standard for ink cartridges came into effect in December 2006. It was created by a consortium of printer manufactures including HP, Canon, Epson and Lexmark after the Office of Fair Trading critisied them for not informing consumers about the lasting power of inkjet cartridges.

The standard is based on a test in which a black cartridge is run continuously alongside a colour one in a printer until the printer's “out of ink message” appears for both. The test conditions include breaks for changing paper and temperature and humidity, which can often vary in a home environment.

However, Whitney Loper, writing systems engineer at HP, said certain oversights and time constrictions have meant that the standard is not a true measurement of cost of ownership.

“Whilst we welcome the standard as an overall way of regulating the industry and giving consumers information, there are some important aspects that we feel have been left out,” she said at the HP Lab event taking place in Portugal this week.

“For starters the standard specifies that a printer manufacturer must run the test continuously until the ink runs out, however this is not indicative of a true consumer print which will often span across months of stopping and starting.

“Time constraints have stopped this. It takes a week for a continuous print, so conducting the test to consumer conditions would take too long,” she added

Printers often perform much better on a continuous print then they would by stopping and starting because ink gets stuck in nozzles and causes ink to fade.

Loper outlined the problems that arise with such an oversight, by disclosing results of HP research that tested the print quality of stopping and starting over a week with a four hour stop and starting rate. It found that this method put a strain on the ink and fading occurred far more quickly than that in a continuous test.

“This is something we have said all along but we have had to compromise with certain aspects of this standard because of the amount of manufacturers and industries taking part,” said Loper.

She also claimed the testing did not take into account the differing absorbtion rates of other types of paper, as “consumers like to print photographs on glossy paper”.

Although HP has said that the standard will probably not be approved until the end of 2008, it suggested that a working draft examining how different photo inks perform on the different media’s will be out within the next few months.