movie was converted to PsF format and recorded to HD-D5 videotapes. This allowed for the creation of a digital master that was nearly identical to the original film, and made it possible to edit digitally at the native frame rate. The same digital master appears to be used for the 2006 Blu-ray Disc transfer of the movie. PsF has been recognized by Recommendation ITU-R BT.709 as a legitimate way to transport progressive frames within an interlaced system. 25PsF and 30PsF rates have been added to the specification in addition to the more established 24PsF. "Fractional" frame rates, having the above values divided by 1.001, are also permitted; the resulting 23.976PsF and 29.97PsF rates are used in 59.94 Hz systems. No change from 59.94 Hz systems to 60 Hz (although provided for and anticipated) has occurred allowing display on analog NTSC color televisions and monitors after down-conversion and encoding. PsF became a means of initial image acquisition in professional Sony video cameras. It is employed in HDCAM and XDCAM video cameras, including the HDW-F900 CineAlta camera which was used by George Lucas for creating Star Wars, Episode 2, and by Alexander Sokurov for creating Russian Ark fully in the digital domain. Similar technologies 2:2 pulldown (TV broadcast) 2:2 pulldown is widely used in 50 Hz interlaced television systems to broadcast progressive material recorded at 25 frame/s, but is rarely used in 60 Hz systems. The 2:2 pulldown scheme had originally been designed for interlaced displays, so fine vertical details are usually filtered out to minimize interline twitter. PsF has been designed for transporting progressive content and therefore does not employ such filtering. PALplus film mode (TV broadcast) PALplus utilizes a digital stream embedded in the interlaced analog TV signal called widescreen signaling, which, among other data, describes whether the signal should be treated as interlaced ("camera mode") or progressive ("film mode"). Video recorders PsF is utilized in some DV, HDV and AVCHD camcorders for 25-frame/s and 30-frame/s progressive-scan recording. To achieve this, the camera acquires 30 (NTSC) or 25 (PAL) independent images per second. These images are output as 60 (NTSC) or 50 (PAL) interlaced fields. The result is a progressive-scan content, which is compatible with traditional interlaced scanning systems. This is how Sony described the progressive recording mode in the operating guide for a 60 Hz ("NTSC") Sony DCR-HC96 camcorder: The booklet for the 50 Hz ("PAL") Sony DSR-PD175P camcorder