Sony T90 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Sony T99 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 T90 and T99 sensor size comparison.
Sony T90 and Sony T99 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.