High Definition - the camera family cont'd...
In April 2003 Cooke optics presented a useful fast zoom. T1.7 8-46mm. Front element is 150mm and weight is 6 kilos. Unfortunatly a 6 inch matt box is needed with this lens.
Panavision Lenses
The Panavision lenses are not anamorphic, so how did Lucas make a cinemascope aspect ratio image from a 16 x 9 frame? He "extracted" a Sony term, used to describe cropping the centre portion of the frame. He started with 1080 lines in camera he ended up with 700 lines to transfer to film.
It is not surprising then, that today a good crew, shooting academy aspect ratio and working with latest lenses can surpass the horizontal resolution of Star Wars.
In May 2004 Canon launched a converter that fits between HD lens and camera that refocuses the cinemascope aspect ratio of the image then squashes it to fill the 16 x 9 frame. The other option for cinemascope is to use a Viper in scope mode, where full height 1920x1080 pixels are reassigned to 2.35:1 aspect ratio.
Some productions chose HD because they have a high shooting ratio, but in some cases a large and heavy zoom is counter productive as its mass makes it quite difficult to quickly reset the camera.
A production team should think carefully about the crew size , schedule and location before deciding which camera system or lenses to use.
The other way to create a narrow depth of field is to use an optical relay lens. These have been used in standard definition for years.
Basically a lens that is designed for a larger format say 35mm motion picture lenses is fixed to an adapter that refocuses the image onto the 2/3 inch ccds. The narrower depth of field of the larger format lens is maintained. The adapter absorbs 1 stop of light and usually degrades the image a little.
The latest version of this device features a fast spinning ground glass where the image is formed from a 35mm format lens. The image is then refocused onto the 2/3 inch chips. It creates a unique soft texture, once again with a loss of light.
After the lens, next in line is a prism. This splits the light into three separate image planes. There doesn't seem to be much difference between the prisms used by manufacturers. Fixed to the prism with incredible accuracy are three ccd sensors. The ccd has been the choice of sensor for the last 12 years but is now being challenged by CMOS sensors. However Fuji have recently announced some remarkable breakthroughs in ccd design for 35mm digital still cameras, including a ccd that has two pixels per photo site. One is large the other small. The small one naturally is less sensitive to light (by 2 stops) the outputs of the two photodiodes are combined by processing to produce a increase in dynamic range to rival film, according to Fuji anyway! It is feasible that this technology will find its way into video cameras.
CCDs
The CCD is packed with millions of photo diodes. To form a PAL standard definition frame there are around 750Hx 625V diodes on each of 3 ccds forming a picture, in a HD camera there are either 1920Hx1080V or 1280H x 720V pixels on each of the ccds. Except for the Viper that is which has a total of 9 million pixels more on the Viper later.
There are studio cameras that are multi standard but there are no camcorders that are multi standard ie that record both 720p and 1080p formats.
All of the camcorders have removable smart media that store camera set-ups and use the B4 mount (except Panavised f900) Some of the box cameras use c mount lenses.
All can use a range of batteries and camera accessories such as LCD monitors. Panasonic use the Sony style base plate, a version of which has been redesigned by Chrozial so it is very solid indeed. Matt boxes are a nightmare if you mix and match base plates as the base plates vary in thickness.
The advent of the Panavision Sony Genesis opens a new door and is the first digital cinematography camera to crawl from the video swamp and not be clubbed to death as it hit the beach.
The Sony HDWf900 cine alta camera, HDW750 and HDW730 camcorders record on the HDCAM format. This format records a 1440Hx1080V frame. How do Sony convert 1920H to 1440H? They are very coy about this "sampling" it is described as a kind of coil compression.
As the human eye is more attuned to vertical than horizontal resolution this loss of quality is less than you would imagine. On replay the frame is converted to 1920x1080.
How much horizontal resolution is lost on a HD recording? Try monitoring a live HD camera on a 24 inch monitor, recording a scene and switching between live and playback.
Most of the time the viewer cannot see a difference between the live output and the playback. The live output from the camera head is full quality 1920 x1080. However there are artifacts with both the sampling and the HDCAM compression that can be seen by a computer trying to key a blue screen. Usually in the form of a single pixel between blue screen and subject that represents.... neither.
Fast motion against blue screen should be shot at a higher shutter speed to reduce motion blur, then motion blur added after the key is made in post.
Sony HDW750
The HDW 750 and HDW730 series has an inbuilt 1920x1080 HDSDI output as well as a down convertor (SDI) output whereas the f900 needs adapters. The f900 has 12 bit processing and the 750/730 is 10 bit. The f900 has a greater range of tones and colours at the expense of a larger heavier and more power hungry camera not to mention it is more expensive, certainly if you add up the cost of down conversion and HDSDI output adapters.
The 750p and 730 have a loop record function as an optional extra, where a RAM buffer holds 8 seconds of video and audio as in the DVW790. So it is possible to roll tape thus recording the previous 8 seconds, a useful feature for wildlife and news cameramen.
This feature is also used for timelapse but exposure duration does not exceed 1/25th second..
The HDSDI output via a single cable carries full quality uncompressed HD picture, with timecode and audio in perfect synch.
The f900 has a analogue HD output that needs 3 cables to carry the picture and separate cables for sound and timecode. The upside is that this Y PB PR signal requires no additional expensive decoding card in the monitors. But one BNC cable is defiantly easier to work with than three.
The f900 has undergone various upgrades the latest is a significant improvement to dynamic range and a lower noise level. Producers should check exactly what upgrades have been installed if quality is a issue. The mark 3 camera has a different block that eliminates green flare that some times arises when shooting pinpoints of light. A cine gamma curve is available for mark 3 cameras.
