Sony T900 has a
12.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized CCD sensor . On the other hand, Sony TX20 has a
16.0MP 1/2.3-inch (6.17 x 4.55 mm ) sized BSI-CMOS sensor and features BIONZ processor.
Below you can see the T900 and TX20 sensor size comparison.
Sensor Size and Resolution Comparison image of Sony T900 and Sony TX20 Cameras
Sony T900 and Sony TX20 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. On the other hand, since Sony T900 has 32% larger pixel area compared to Sony TX20, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.
Sensor size sets the circle of confusion, so it drives how much depth of field each
of these bodies gives you at a given aperture. You can calculate it exactly for the
Sony T900
or the
Sony TX20 ,
including hyperfocal distance.