In the previous newsletter we went right back to the origins of the telecine machine. What it is, the function it performs and the development through the years to its current form. We examined the Photo Conductive film (PCF) chain type device and how it developed and its application in our high technology industry. We also then covered the flying spot telecine, and the CCD telecine.  In this final article we will look at the Pulsed LED/Triggered three CCD camera systems, take a quick look at the digital intermediate, touch on requirements for HD, and the requirements for DVDs.  In Focus will attempt to keep these techno talk articles simple and concise, so apologies in advance to our more technical readers who may be expecting a bit more depth - the purpose of these articles is to introduce newcomers to the industry to technical topics.

Pulsed LED/Triggered Three CCD Camera system

mar-TelecinesIn 2004, MWA Nova, Berlin introduced Flashscan, a new concept in film transfer systems. Using continuous film motion, an array of multiple red, green and blue LEDs is pulsed at just the moment a frame of film is precisely positioned in front of the optics of a high-resolution, three-CCD, triggerable industrial process control camera. The LED array pulse triggers the camera and sends the single, non-interlaced image of the film frame to a digital frame store, where the electronic picture is clocked out at the applicable TV frame rate for PAL (or NTSC.)

This approach enables the film speed to be varied - without flicker - in real time from three to twenty-five frames per second (FPS) in PAL or six to thirty FPS for NTSC units, while introducing the appropriate pull-down for the television system involved. The output can be progressive (non-interlaced) or interlaced. The framestore also provides multiple digital and analogue outputs.

The Pulsed LED/Triggered camera concept was extended to 16mm and 35mm in the company's flashtransfer system for 16 and 35mm film. A camera with larger CCD chips is used, and the company's well regarded server driven MB51 magnetic film transport is the film handling platform. On both platforms, the colour of the LED array can be varied to achieve accurate colour balance, which can be further fine tuned using the camera's black, white and gamma controls. "De-pinking" faded film and transfer of colour negative film can be handled using the two colour correction systems. The SDI output enables high-end devices like digital noise reduction systems and DaVinci style colour correctors to be connected.

The company introduced flashscan HD, a high definition version of the 8mm/Super8 product, at IBC 2008. The new unit can transfer film in HD at faster than real-time speeds. It uses a three-CMOS chip HD camera and hardware processing of the video to output all major HD formats. Software controls film motion and colour correction, which can be tied to cues for real-time colour correction.

Digital intermediate systems and virtual telecines

mar-Telecines2Telecine technology is increasingly merging with that of motion picture film scanners; high-resolution telecines, such as those mentioned above, can be regarded as film scanners that operate in real time. As digital intermediate post-production becomes more common, the need to combine the traditional telecine functions of input devices, standards converters, and colour grading systems is becoming less important as the post-production chain changes to tapeless and filmless operation.

However, the parts of the workflow associated with telecines still remain, and are being pushed to the end, rather than the beginning, of the post-production chain, in the form of real-time digital grading systems and digital intermediate mastering systems, increasingly running in software on commodity computer systems. These are sometimes called virtual telecine systems.

Video cameras that produce telecined video and "film look"

Some video cameras and consumer camcorders are able to record in progressive "24 frame/s" (actually 23.98 frame/s) or "30 frame/s" (actually 29.97 frame/s) in NTSC, or 25 frame/s (PAL) mode. Such a video has cinema-like motion characteristics and is the major component of so-called "film look" or "movie look".

For most "24 frame/s" cameras, the virtual 2:3 pulldown process is happening inside the camera. Although the camera is capturing a progressive frame at the CCD, just like a movie camera, it is then imposing an interlacing on the image to record it to tape so that it can be played back on any standard television. Not every camera handles "24 frame/s" this way, but the majority of them do.

Cameras that record 25 frame/s (PAL) or 29.97 frame/s (NTSC) do not need to employ 2:3 pulldown, because every progressive frame occupies exactly two video fields. In the video industry, this type of encoding is called Progressive Segmented Frame (PsF). PsF is conceptually identical to 2:2 pulldown, only there is no film original to transfer from.

Digital television and high definition

mar-Telecines3Digital television and high definition standards provide several methods for encoding film material. Fifty field/s formats such as 576i50 and 1080i50 can accommodate film content using a 4% speed-up like PAL. 59.94 field/s interlaced formats such as 480i60 and 1080i60 use the same 2:3 pulldown technique as NTSC. In 59.94 frame/s progressive formats such as 480p60 and 720p60, entire frames (rather than fields) are repeated in a 2:3 pattern, accomplishing the frame rate conversion without interlacing and its associated artefacts. Other formats such as 1080p24 can decode film material at its native rate of 24 or 23.976 frame/s.

All of these coding methods are in use to some extent. In PAL countries, 25 frame/s formats remain the norm. In NTSC countries, most digital broadcasts of 24 frame/s material, both standard and high definition, continue to use interlaced formats with 2:3 pulldown. Native 24 and 23.976 frame/s formats offer the greatest image quality and coding efficiency, and are widely used in motion picture and high definition video production. However, most consumer video devices do not support these formats. Recently however, several vendors have begun selling LCD televisions in NTSC/ATSC countries that are capable of 120Hz refresh rates and plasma sets capable of 48, 72, or 96Hz refresh. When combined with a 1080p24-capable source (such as most Blu-ray players), some of these sets are able to display film-based content using a pulldown scheme using whole multiples of 24, thereby avoiding the problems associated with 2:3 pulldown or the 4% speed-up used in PAL countries.

DVDs

On DVDs, telecined material may be either hard telecined, or soft telecined. In the hard-telecined case, video is stored on the DVD at the playback framerate (29.97 frame/s for NTSC, 25 frame/s for PAL), using the telecined frames as shown above. In the soft-telecined case, the material is stored on the DVD at the film rate (24 or 23.976 frame/s) in the original progressive format, with special flags inserted into the MPEG-2 video stream that instruct the DVD player to repeat certain fields so as to accomplish the required pulldown during playback. Progressive scan DVD players additionally offer output at 480p by using these flags to duplicate frames rather than fields.

NTSC DVDs are often soft telecined, although lower-quality hard-telecined DVDs exist. In the case of PAL DVDs using 2:2 pulldown, the difference between soft and hard telecine vanishes, and the two may be regarded as equal. In the case of PAL DVDs using 2:3 pulldown, either soft or hard telecining may be applied.

Next month we will look into non-linear editing, cover its history, development and where it stands in the market place at present. If there are any other areas you would like us to cover, or if you have any questions about the items already covered, please email us.