SD – This just means Standard Definition as opposed to High Definition or HD. NTSC and PAL are SD video frame sizes. NTSC – This is the standard for SD television monitors in North America, Japan, South Korea, and parts of South America as well. It features a frame size of 720×480 or 720×486, and a frame rate of 29.97 frames per second. The pixels are non-square, since the format was designed before the advent of the personal computer. PAL – This is featured in Europe, Africa, South America, Australia, and much of Asia. For simplicity, we have lumped another standard called SECAM in with PAL – they are pretty compatible, at least as far as digital video is concerned. PAL (SECAM) features a frame size of 720×576 pixels, and a frame rate of 25 frames per second. The pixels are also non-square, but in a different orientation than NTSC. HD – iStock offers two sizes of HD – 1280×720 and 1920×1080. These files originate from either HD capable cameras or computers. The 1280×720 size is common