can easily calculate how many remaining green apples there are, as 20 minus 15 would leave a difference of five. When engineers sought to process and record in real time the huge amount of digital data needed to make the first digital video tape format, keeping the Y, R-Y, B-Y or YUV algorithm was key to simplifying and reducing the initial picture information sampled, saving valuable space. 4:2:2 is Y, R-Y and B-Y; not RGB; 4:2:2 is often erroneously quoted as 4 meaning red, and the remaining 2s standing for green and blue. If this were true, it would produce an uneven recording of green and blue data compared to red. In a given small sample of the video picture - for instance the first four pixels going across horizontally in the top-left corner of the screen, the first "4" means that the more important luminance/black-and-white picture detail was sampled in every pixel in that 4-sample. The next two 2s mean that R-Y and B-Y were sampled at every other pixel, skipping the one in-between. The eye should not be able to see the two in-between pixels not having the actual color information that the originating camera recorded - previous color pixel is simply replicated. Thus with 4:2:2, all color, red, green and blue, is sampled at half the rate of the black-and-white (luminance) picture detail. You could say that 50% of the color is actually recorded - because for the TV screen, it was good enough for the human eye. The popular 1995/96 1/4-inch DV/DVCAM/DVCPro format had a component digital YUV sampling of 4:1:1, meaning only 1 out of 4 pixels or 25% of the color is actually recorded, which is why the color looks "muddy" and not as vibrant when compared to any 4:2:2 recording. This further made perfect green screen mattes impossible on the format. The DV format further compressed the digital data at 5:1, meaning compromising the picture information by 80% to get 25 million bits per second onto a small tape moving at a slow speed. Compare the DV quality to 1986's D1, with 4:2:2, no compression, and 173~226 million bits per second of data preserved. Modern high definition video recorders - like Sony's HDCAM-SR format - SR stands for superior resolution - have the ability to switch between 4:2:2 and full RGB recording for giant-screen motion picture work, thus RGB is sampled at every