Pentax K100D has a
6.0MP APS-C (23.5 x 15.7 mm ) sized CCD sensor . On the other hand, Nikon D90 has a
12.0MP APS-C (23.6 x 15.8 mm ) sized CMOS sensor .
Nikon D90's sensor provides 6MP more than Pentax K100D'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 K100D and D90 sensor size comparison.
Sensor Size and Resolution Comparison image of Pentax K100D and Nikon D90 Cameras
Pentax K100D and Nikon D90 have almost the same sensor size, so neither of them has any significant advantage over the other in terms of providing control over depth of field when used with the same focal length and aperture.
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
Pentax K100D
or the
Nikon D90 ,
including hyperfocal distance.
