Two main new features were changed on GeForce 7800 GTX in order to increase the image quality: High Dynamic Range (HDR) and Transparency Anti-Aliasing.

High Dynamic Range (HDR)

The problem of lightning is that in the real world lights have unlimited bright, and  the human eye has a perception of 14 dB  (10^14:1), but the video card using a standard 32-bit integer buffer is only capable of reproducing 2.4 dB (255:1), because it uses only 8 bits to store each video component (R, G, B and alpha). GeForce 7800 GTX, in order to increase video quality, uses a 128-bit register for HDR, using 32-bit for each video component. The difference you can see on Figure 5.

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Figure 5: A comparison between a non-HDR system (32-bit register, 8-bit for each video component) and a HDR system using a 128-bit register (32-bit for each component).

GeForce 7800 GTX uses its floating-point engine to produce HDR, not integer like other video cards.

Transparency Anti-Aliasing

The best way to describe the new Transparency Anti-Aliasing mode is to compare the standard anti-aliasing with this new feature.

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Figure 6: Standard anti-aliasing.

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Figure 7: Transparency anti-aliasing.