Kodak Astro AZ651 has a
21.0MP (1/2. ) sized CMOS sensor . On the other hand, Olympus TG-4 has a
16.0MP (1/2. ) sized BSI-CMOS sensor and features TruePic VII processor.
Kodak Astro AZ651's sensor provides 5MP more than Olympus TG-4's sensor, which gives a significant advantage in real life. You can print your images larger or crop more freely.
On the other hand, please keep in mind that Max sensor resolution is not the only determinant of resolving power. Factors such as the optical elements, low pass filter, pixel size and sensor technology also affects the final resolution of the captured image.
Below you can see the Astro AZ651 and TG-4 sensor size comparison.
Kodak Astro AZ651 and Olympus TG-4 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.