luminance information over hue and particularly saturation, switching between the three components as needed, compared to the more regular interleaving of full-resolution luma () with individual half- or quarter-resolution chromas ( + ) as used by later digital video standards. This offered considerable efficiency benefits over RGB. As the Amiga design migrated from a games console to a more general purpose home computer, the video chipset was itself changed from HSV to the modern RGB color model, seemingly negating much of the benefit of HAM mode. Amiga project lead Jay Miner relates: The final form of Hold-And-Modify was, hardware-wise, functionally the same as the original HSV concept, but instead of operating on those three descriptive components (mostly prioritising the V component), it modifies one of the three RGB color channels. HAM can be considered a lossy compression technique, similar in operation and efficiency to JPEG minus the DCT stage; in HAM6 mode, an effective 4096-color (12-bit) playfield is encoded in half the memory that would normally be required - and HAM8 reduces this still further, to roughly 40%. There is a however a payoff for this simplistic compression: a greater overall color fidelity is achieved at the expense of horizontal artifacts, caused by the inability to set any single pixel to an arbitrary 12- (or 18, 24) bit value. At the extreme, it can take three pixels to change from one color to another, reducing the effective resolution at that point from a "320-pixel" to approximately "106-pixel" mode, and causing smears and shadows to spread along a scanline to the right of a high contrast feature if the 16 available palette registers prove insufficient. "Decompression" of the HAM encoded color space is achieved in realtime by the display hardware, as the graphics buffer data is being displayed. Each encoded pixel acts as either a normal index to the color palette registers, or as a command to directly alter the value held in the output DAC (somewhat like updating just one-third of the active palette register), and is immediately acted on as such as it passes through the chipset. Usage When the Amiga was launched in 1985, HAM mode offered a significant advantage over competing systems. HAM allows display of all 4096 colors simultaneously, though with the aforementioned limitations. This pseudo-photorealistic display was unprecedented for a home computer of the time and allowed display of digitized photographs and rendered 3D images.