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MillimeterHDV@Work
Aug 8, 1997 5:12 PM
What is Optimal Exposure? Part 1 of 4
Lesson 1: Do not approach a camcorder on the basis of what you are used to. Look at what the new camera offers you.
When the JVC HDV camcorders were introduced two years ago, many folks criticized them because they did not offer independent control of shutter speed and aperture. Critics claimed it was impossible to shoot without both controls.
Recently, I read a review of Sony’s new HDR-HC1 HDV camcorder that put forth the same kind of criticism, which I will paraphrase as: “There are three modes of exposure control: auto, auto with manual shutter-speed setting, and manual lighten/darken with or without manual shutter-speed setting. The latter mode does ‘stay set,’ so exposure will not change if lighting changes.” Unfortunately, “While you can control shutter speed manually, you have no way to adjust the aperture.” Moreover, “Sony doesn't give you any F-stop readings.”
Because it is likely that forthcoming low-cost, single-chip HDV camcorders designed for prosumers and consumers will have similar control restrictions, it is time to look critically at these criticisms.
My reaction to the JVC criticism was, and remains, that these comments overlook the fact that exposure is a function of a perfect relationship between shutter speed and aperture. Set either one, and there is only one “optimal” value for the other.
Of course, there are many possible definitions of optimal—many that go far beyond exposure. For a DP using a Panavision-modified Sony HDCAM camcorder, a calibrated HD monitor, waveform and vector scopes, a remote CCU (camera control unit), and a realtime color correction system—optimal means recording video that is very, very close to what the director wants the audience to see in a theater.
Clearly, for most consumers and most prosumer videographers, this level of “in-field” optimization is not needed and is not practical.
From my engineering viewpoint, optimal means the information being transmitted/recorded uses all the bits in the digital “words” representing audio and video samples. For example, for 16-bit digital audio, an audio signal is optimum when it includes values near 0 and near 65,536. You do not want all the audio information bunched up near 0 or near 65,536.
Looking at a histogram of video signal values, it should not show all the visual information clustered at either the minimum or maximum brightness (IRE) level. Ideally, it should be spread across the full range of levels so the recorded grayscale range of the video signal has the maximum number of levels. This yields maximum grayscale resolution.
Interestingly, the HDR-HC1 includes a histogram display of the video signal so you can achieve this goal in the field. The HC1 is the first consumer/prosumer camcorder to offer this valuable feature.
To obtain an optimum video signal we have four available control functions: ND setting, video gain level, shutter speed, and aperture. The ND setting simply brings very bright scenes into a range that can be handled by the camera’s electronics. Other than sometimes being use to minimize depth of field, it has no “creative function.” (A high ND value forces the aperture open, thereby minimizing DOF.)
In Part 2, we will look at the role of video gain and shutter-speed control in obtaining an optimum exposure.
JustEdit will exhibit new HD playout video servers at IBC
At IBC2005, JustEdit will showcase for the first time in Europe a new range of high-definition video servers, HD500 and HD800. The configurations available are 1 Ch (vsnmatic) and 1-2 Ch (vsnnews). The new HD servers are based on the standard MPEG-2, MP@HL up to 80Mbps, in 720p and 1080i resolutions, designed for a tapeless network environment and compatible with the most popular NLE HDV file formats.
Vsnairnews HD500 is the live program video server integrated with the digital newsroom system vsnnews, which offers a proven and complete solution for HDV managed production.
Vsnnews guarantees an optimal workflow in the newsroom, integrating rundown creation tasks, text editing, content ingest, resource management, storage, cataloguing, network editing with voiceover from the journalist's workstation, archive, real-time titling, teleprompter, and automatic news rundown web publishing.
Using the same file formats, vsnmatic HD800 is the master control room playout video server and automation software for 24x7 mission critical on-air broadcasts. It can control existing equipment (routers, VTR’s, titling system, etc.). Vsnmatic plays back all video files received through the network from the NLEs. It also enables connection/disconnection between different TV stations and integrates with other vsn systems such as vsnairnews.
The vsnmatic HD800 system includes the video server, the automation software, vsnmatic remote (to prepare rundowns remotely or via the Internet) and vsnpubli (advertising management software). The server is available in a 4 RU rack format, with an external 3.2TB storage in 2 RU, which signifies 85-hour capacity for HD files (80Mbps) or 250-hour capacity for HDV files (25Mbps).
JustEdit, S.L. is a leader in state-of-the-art video servers and software for TV. There are currently over 300 TV channels around the world using vsn automated systems.
Vsn is a cost-effective video server and automation software platform for TV stations. It features modules for digital newsroom, ingest, network editing, archive, graphics, web publishing, master control room playout, legal compliance, and sms TV.
Red Giant Software releases Primatte Keyer 3 and Key Correct Pro
Red Giant Software, publisher of a line of professional desktop tools including the award-winning Magic Bullet technology, today announced the availability of Primatte Keyer 3 and Key Correct Pro. Primatte Keyer’s enhanced versatility adds increased functionality to the production pipeline of independent filmmakers and visual effects artists. Key Correct Pro is a set of 15 tools to help motion graphic and visual effects artists achieve more realistic composites.
Primatte Keyer, published under exclusive agreement with Photron USA, is the most advanced software version for After Effects, Discreet combustion, and Avid AVX—enabling artists to extract keys from any color background for compositing. The software overcomes matte extraction challenges including uneven lighting, subtle shadows, and edge light contamination (spill) prior to compositing. New features include:
- New Deartifacting input correction for all formats, including DV and HDV
- New feature-rich library and accuracy inline with other Primatte versions for Discreet, Shake, etc.
- Updated UI and new split screen View modes for more efficient keying
- Alpha channel adjustment integrated into the keyer
- Integrated secondary spill removal, simple and accurate Color Matching, and Light wrap built in to the keying interface
Key Correct Pro is a set of 15 plug-ins designed to help AE users create better composites with built-in keying tools. The plug-ins can be in used in combination with any keyer to better enhance the final result. Features include:
- Accurate matte feather tools
- Color Matching plug-in with automatic matching and color balance adjustment
- Alpha cleaner plug-in for fixing noise and filling holes in mattes
- Complete support for 8- and 16-bit operations for all plug-ins
“With the market explosion of HDV cameras, Primatte Keyer fills a technology gap with quality tools at an affordable price. We also proud to release a new compositing tool with 16-bit support and other fine-tuning features for the best end result. We look forward to feedback on how these unique product offerings are used in future productions,” said Sean Safreed, Partner at Red Giant Software.
Pricing and Availability
- Primatte Keyer 3 for Adobe After Effects ($695 USD). Updates to Discreet combustion and Avid AVX versions will be available in Q4 2005.
- Key Correct Pro ($395 USD)
- Composite Wizard customers can upgrade to Key Correct Pro for ($149 USD)
Visit www.redgiantsoftware.com for additional product information.
Telestream Flip4Mac adds Windows Media encoding support for Apple Compressor 2
Telestream, the provider of Flip4Mac digital media tools for the Macintosh, today announced release of Flip4Mac WMV Studio Version 1.0.6, which adds Windows Media encoding support for Apple Compressor 2. Flip4Mac WMV products are comprised of QuickTime components that enable Macintosh OS X users to make, edit, and play Windows Media from within their favorite QuickTime-based applications. For Apple Compressor users, the Flip4Mac WMV Studio update provides, for the first time, batch encoding of Windows Media files on the Mac. In addition, the newly released Flip4Mac WMV Player Version 1.0.2 adds compatibility with more Windows Media on the Web.
“Our goal has been to expand our Windows Media support to any QuickTime-based application, and support for Compressor is key to reaching that goal,” said Barbara DeHart, Telestream’s Flip4Mac program manager. “We recognize the popularity of Compressor as a compression tool and Windows Media as a streaming format, and we are pleased to provide the encoding capability that brings these two together.”
The ability to export Windows Media 9 standard-definition and high-definition content directly from within Compressor 2 simplifies multiformat content creation for Final Cut Pro users. Compressor 2 is a video and audio compression application that gives Final Cut Pro users control over encoding. This includes the ability to encode several clips in one batch operation to a wide variety of formats and perform advanced format conversions at the same time. Flip4Mac eliminates the platform challenge and the many steps previously required to create Windows Media, including exporting the file, moving it to a PC, and then encoding it using another software application.
"Windows Media support is essential for most content creators because it's the de facto standard on PCs," said industry commentator and Final Cut Pro expert Philip Hodgetts. “Flip4Mac support for encoding direct from Compressor 2 simplifies the workflow and gives me more time to concentrate on the creative aspects of the craft. Having batch processing support, with the pre-processing functions of Compressor 2, just simplifies my life.”
Support for Compressor 2 is now available in Flip4Mac WMV Studio and WMV Studio Pro Version 1.0.6. Compatibility with more Windows Media web content is now available in Flip4Mac WMV Player and WMV Player Pro Version 1.0.2, as well as in WMV Studio and WMV Studio Pro v1.0.6. Flip4Mac products are available for immediate online purchase at www.flip4mac.com. Existing Flip4Mac WMV Studio/Studio Pro and Player/Player Pro customers may download free upgrades from the Web at www.flip4mac.com/support.htm.
