Capability and size of the sensor grid is everything. And in the heart of the Nikon D90 lies a slightly modified Sony IMX021 CMOS (Complementary Metal-Oxide Semiconductor) sensor grid, churning out 4288x2848 photosites grid image via a 12-bit A/D converter. Now, that's good enough for most users.12 bits-per-pixel tonal range may not seem like much, but it translates into the ability to render 4096 shades of an individual color - Red, Green & Blue. This alone result in image quality that even our human eyes can no longer differentiate.
If you are familiar with the CCD/CMOS story, one would agree that CMOS generates more noise in its harder-to-design, cheaper-to-make model. Speaking of noise, do take note of the following to minimize noise being introduced in your shoot
- Avoid long shutter exposure
- Shots are exposed to low blue or red wavelength of light
- Very warm environment
- High ISO set