Samsung TL225 has a
12.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor . On the other hand, Samsung ST6500 has a
16.0MP 1/2.3-inch (6.08 x 4.56 mm ) sized CCD sensor .
Below you can see the TL225 and ST6500 sensor size comparison.
Samsung TL225 and Samsung ST6500 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 Samsung TL225 has 32% larger pixel area compared to Samsung ST6500, it has potential to collect more light on pixel level hence have less noise in low light / High ISO images.