Sony is set to add higher resolution image sensors to several of its digital still camera models.

The DSC-W55 and W35 both sport 7.2Mp (megapixel) image sensors, which is an upgrade on the 6Mp W50 and W30 models currently on sale. Similarly the DSC-S650 and S-700 both offer a 1Mp jump over the current 6Mp S600 model.

The image resolution bump puts the W35 and W55 at the same level as Sony's W70 model. All three cameras offer 7.2Mp resolution while the top-of-the-line W100 model packs an 8.1Mp sensor.

Other major features remain unchanged. All four cameras have a 3X optical zoom lens, blur-reduction setting and internal memory so some pictures can be taken without a memory card. They all accept Memory Stick Duo-type memory cards.

The W35 and W55 will be available in the US in February for $180 and $200 respectively. Both the current W30 and W50 cost $200 so the prices represent a drop for the former model and a higher-spec at an unchanged price for the latter camera. The S650 will go on sale in the same month for $150 and the S700 will be available from March for $180.

Sony will begin accepting US preorders online from 23 January.

Overseas launch plans have not been announced, but Sony typically follows with local announcements within days or weeks.