Sony W220 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Sony H55 has a
14.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor and features Bionz processor.
Below you can see the W220 and H55 sensor size comparison.
Sony W220 and Sony H55 have the same sensor sizes so they will provide same level of control over the depth of field when used with same focal length and aperture.