By Katie Marsal

Published: 06:30 PM EST

When Apple revamped its MacBook and MacBook Pro lineups on Tuesday, the company also quietly changed its methods of reporting battery life and also made clear the eco-friendliness of the notebooks, among other changes.

Although first hinted at in its claimed 5 hours of use for the MacBook Air, Apple has now completely changed its approach to measuring battery life with the introduction of the new MacBook lineup.

Instead of reporting the theoretical peak battery life of each system -- a method sometimes criticized for its at times unrealistic conditions -- Apple now bases the figures supplied for all its notebooks on a "wireless productivity" test. The benchmark assumes a user is browsing various websites on Wi-Fi with the screen set to half brightness. In these conditions, the 15-inch MacBook Pro achieves 5 hours of use, while both the 17-inch MacBook Pro and the regular MacBook run for up to 4.5 hours.

This explains why battery life has, at least superficially, gone down despite Penryn's power improvements over the previous generation. Apple press spokesman Anuj Nayar has informed Ars Technica that, if anything, performance has gone up: previous models often expired sooner in the same conditions.

Apple has in the past regularly conducted three different tests to determine how the notebook runs under ideal, moderate, and extreme conditions, Nayar adds. Previous claims always cited the light-duty "highway test," which was allegedly confusing to users. The wireless productivity test splits the balance between this and a DVD playback test, which is often considered one of the hardest tests thanks to its taxing the energy-hungry DVD drive, CPU, and video hardware.

The new metric is not the only undocumented change by the Mac maker, which also notes that its new systems should be more environmentally friendly than old models -- though not as clean as demanded by Greenpeace and other activist groups. Apple describes the "majority" of either system's circuit boards and internal cabling as free of toxic brominated flame retardants (BFRs) and PVC plastic. In his open letter, company chief Steve Jobs said he hoped Apple would completely eliminate both materials from Macs by the end of this year.

The 17-inch MacBook Pro's new LED-backlit option does continue to meet self-imposed goal of moving to mercury-free displays, though the default display uses a mercury-based cold-cathode fluorescent (CCFL) screen.

Other changes known to have been made to the systems are subtle, but worth noting. Buyers of the 13.3-inch MacBook may be disappointed to learn that the new processors, while faster overall, represent a step backwards in terms of their onboard memory cache: the earlier 2GHz and 2.2GHz Core 2 Duo processors carried 4MB of Level 2 cache, while the new models sport only 3MB each.

Also, Apple has for the first time supplied different versions of Bluetooth with its notebooks: the MacBook Pro supports the more recent 2.1 version of the wireless technology, which permits a far simpler pairing process as well as better security and power use. Standard MacBooks continue to use Bluetooth 2.0. No explanation has been given by Apple for the difference.

Prospective buyers of either system might be disappointed to know that the Apple Remote is now a $19 option for both systems rather than a standard, pack-in feature.