Multimedia
Blogs
Forum
Affordable HD
Whitepapers
Newsletters
Events
Advertisers
DCP Directory
MillimeterHDV@Work
Sep 12, 1997 10:45 AM
What is Optimal Exposure? Part 3 of 4
by Steve Mullen
In Part 2, we examined the role of shutter speed in obtaining an optimally exposed image. Now we will look at the aperture control.
If we wish to restrict shutter speed to a creative function rather than an exposure function, that leaves the camera’s aperture as the only way to control exposure. This, of course, is the case with professional still and video cameras. A lens on these cameras always has a convenient ring with which to control exposure.
There are two ways to control to a camera’s aperture—directly by manual control or via automatic control. In the latter case, we may need to further adjust the exposure selected by the auto exposure (AE) system—and then lock it. We do this by either setting an AE “bias” in the menu system, or via a manual adjustment during the shot. (We also want to be able to lock the exposure.)
No matter how we control exposure, the question remains: What is our goal? The key is to adjust exposure so that the camera’s full electronic grayscale is used to carry the image. This provides maximum grayscale resolution. (A consumer HDV camcorder, Sony's new HDR-HC1 HDV camcorder has a histogram, as does the pro version of this, the HVR-A1U.) For the photographers out there, this is much like Ansel Adams' Zone System (www.normankoren.com/zonesystem.html), where the full range of film latitude is used to capture the full tonality of an image. To try out this concept: set VF to B&W; adjust so only a few tiny details are white (100 IRE); and some other small areas are full black. Continue to adjust until you get two to three levels of light gray and two to three levels of dark gray, plus two to three levels of medium gray.
Pros will say one must know the current F-stop. Why? It will not help you get the correct exposure because you are either using AE or your own eye. The pro’s quite correct response is that there are side effects of aperture size. Either too small or too large an aperture reduces image quality. Therefore, if you have a professional lens that has been tested so that you know it looks best at f/5.6, you obviously want to adjust all else to set an f/5.6 aperture. However, in the consumer and prosumer world, we do not typically have such data. Thus, we really have no need of the F-stop number.
We do, however, require a visual indicator showing the aperture range and an indication of the current setting. Moreover, if the camera automatically applies gain when the aperture opens fully, then the indicator should include the gain range.
With such an indicator, when you see the aperture is nearly fully open, or that gain being added, you can add more light. If you see that the aperture is nearly closed, you can reduce light. The Sony HDR-HC1, a consumer HDV camcorder that's similar to the HVR-A1U, provides such an indicator.
Shutter-priority cameras (such as the HDR-HC1) have a limitation. If you set the shutter speed for creative reasons—or you set a 1/60 second shutter because you will de-interlace on the way to film—the camera will not allow you to make any exposure adjustments. The AE system will automatically set the aperture and keep it under automatic control. That also means you have no way to lock exposure.
Moreover, if you are shooting under bright light, the aperture may close so far as to reduce image quality. Thus, you might need to add an ND filter.
In Part 4, we will examine what how this framework needs to be extended into your NLE.
Lesson 3: With shutter-priority cameras, you can choose to use either the shutter or aperture for creative control, but not both at the same time. That means you must thoughtfully choose what is most important to control for each shot.
Avid announces October availability of native HDV support
Avid Technology, Inc. announced that it expects to deliver native HDV editing and workflow support in its PC-based Avid Xpress Pro and Media Composer Adrenaline products by October 17, 2005. Customers who purchase either a Media Composer Adrenaline HD 2.x system with an assurance contract or an Avid Xpress Pro HD 5.x system before October 17 may receive free HDV software upgrades when the release ships next month.
“Although HDV is still relatively new as a format, there's no question that it is having a significant impact in the marketplace, with early adoption among broadcasters, postproduction facilities and independent producers,” said Patrick McLean, senior product manager for Avid. “Our customers have been asking Avid to support this new format, and we're pleased to announce that we're delivering it. More importantly, we've invested heavily to ensure that our HDV implementation addresses key customer needs such as mixing HDV with DV and other formats in the same timeline in realtime. When they begin working with HDV, they'll have the same kind of seamless workflow experience as they do when working on an Avid system today.
“I've been beta testing HDV on Avid Xpress Pro for over a month, and one of the best things is that my workflow hasn't changed at all. Avid has clearly put a lot of thought into this implementation – they simply understand how professionals need to work,” said David Benjamin, an editor for IFILM currently working on Team Extreme, a film project for Fuel TV. “Plus, with Avid's rock-solid media management, script-based editing, open timeline, and realtime effects capabilities, I feel truly empowered as an artist, which is more than I can say about the experiences I've had using other HDV-ready NLEs.”
The planned October release of HDV support will be for PC-based systems, and Avid will offer HDV as a free upgrade to customers who purchase either a Media Composer Adrenaline HD 2.x system with an assurance contract or an Avid Xpress Pro HD 5.x system before October 17, 2005. Avid Xpress Pro 4.x customers can purchase the HDV upgrade for US$50.00 MSRP.
AJA introduces new Kona LH 10-bit uncompressed video capture card for FCP
AJA Video, a leading manufacturer of professional video interface and conversion solutions, today announced the immediate availability of its new Kona LH, a 10-bit uncompressed video capture card for editing on the Apple G5 with Final Cut Studio. Kona LH is the only PCI card available for OS X and Final Cut Studio that offers both HD and SD analog and digital I/O, all in one broadcast-quality card.
Considering the various SD and HD formats on the market, the ability to utilize both analog and digital sources makes a lot of sense for today's editors. With the Kona LH, everything is in just one card, simplifying editors' system setup and providing flexibility.
“We recognize what the most popular choices are now for SD and HD in terms of day-to-day workflows, and it makes good sense to roll it all into one product,” says Ted Schilowitz, worldwide product manager, desktop video, AJA Video. “Kona LH is a completely migrated product with the most utilized features of Kona 2 and Io at a breakthrough price, while maintaining the highest standards of reliability and quality that professional editors require and expect from AJA. The ability to bring in and layback to HDCAM, DVCPRO HD, HDV, Betacam SP, Digital Betacam, even VHS, all on one product is really powerful and will make a great solution for our customers that build systems around the Apple platform.”
Supporting native 10-bit uncompressed resolution, Kona LH provides optimum quality for SD and HD, the highest available quality based on SMPTE SDI standards. Kona LH also supports various codecs such as DVCPRO HD, HDV playback, DV50, and many more, with hardware acceleration onboard for the playback of DVCPRO HD, HDV, and Apple's Dynamic RT Extreme. This unique acceleration frees up the G5 to do more, such as more RT.
Kona LH offers unprecedented analog video connectivity on a single PCI card, including 12-bit HD component analog I/O, which is perfect for interfacing to today's HDV cameras and decks, allowing the HDV user to digitize to 10-bit uncompressed, DVCPRO HD, and many other codecs, offering a true professional workflow for the HDV format.
For SD work, the Analog inputs and outputs can be configured as 12-bit SD component/YC/composite, all via three professional BNC connectors. For SD and HD digital I/O, Kona LH offers SDI/HD-SDI input, and two SDI/HD-SDI outputs. Broadcast-grade genlock is also included.
Kona LH's built-in 10-bit hardware downconverter can be used during digitization or playback, allowing the user to bring in HD as SD, and/or output HD as SD for laying to tape or for monitoring, all at 10-bit broadcast quality.
In addition to perfection in video, Kona LH offers true professional audio: native OS X multi-channel audio and 24-bit AES/EBU digital audio at 48kHz for digital production. For ease of conversion, Kona LH also includes hardware sample-rate conversion to allow asynchronous or even different sample rates (32-96kHz), eliminating annoying synchronization hassles and unwelcome snaps, crackles, and pops. Kona LH offers two-channel AES on XLR, two-channel analog on XLR, and eight-channel SDI embedded audio.
Kona LH features dual-monitor desktop viewing for desktop paint and motion graphics program output and also comes standard with a breakout cable and works with the optional KL-Box for rackmounted I/O convenience.
Features Include:
- 10-bit uncompressed SD/HD QuickTime capture card
- SD/HD/analog (component/composite/S-Video)(HD analog component only)
- DVCPRO HD hardware acceleration
- HDV hardware acceleration
- Dynamic RT Extreme hardware acceleration
- High-quality 12-bit video A/D and D/A converters
- SDI or HD-SDI input, two independent SDI/HD-SDI outputs
- 10-bit hardware HD-to-SD downconversion
- Two-channel AES and eight-channel embedded audio
- Two-channel balanced XLR analog audio
- HD/SD genlock
- RS-422 machine control
- Final Cut Pro 5, Motion, After Effects, Combustion, and more
- Cables standard, KL breakout optional
- Three-year warranty
- Technical Support
- $1,790 US list price
For further information, visit www.aja.com.
Canopus Edius to support JVC HD100U HDV camcorder
Canopus, a leader in digital video production, transcoding, and codec technologies, today announced that Edius Pro 3, the company’s powerful realtime video editing solution will support JVC’s new GY-HD100U full-resolution ProHD progressive camera and its BR-HD50U videocassette recorder.
Edius Pro 3 will provide realtime capture and processing for JVC’s 720p format via the IEEE 1394 interface. Edius Pro 3 also provides realtime 720p component output with the company’s Edius NX for HDV, Edius SP for HDV, Edius SD, and Edius HD nonlinear editing systems.
“JVC’s new ProHD camcorder and videocassette recorder are attractive solutions for broadcasters and indie film producers who are making the transition from SD to HD,” said Hiro Yamada, founder and chairman of the board of Canopus. “Add Edius Pro 3’s realtime mixed SD/HD format editing, full frame rate resolution output, scalable design, and a fast, flexible interface, and professionals have the perfect companion for JVC’s outstanding ProHD product line.”
Edius Pro 3 nonlinear editing software provides native editing and realtime processing of uncompressed SD, HD, HDV, DV, MPEG-2, and MPEG-1 formats. With its seamless realtime workflow, Edius Pro 3 lets professionals mix and share video content in multiple formats and work with unlimited video, audio and effects layers, while providing realtime high-quality, on-screen display. Edius Pro 3 delivers increased quality and realtime performance through the company’s acclaimed variable-bit-rate Canopus HQ codec. Edius Pro 3 includes professional features, such as realtime HQ batch capture from 1080i and 720p HDV cameras and decks, advanced audio tools, and precise color correction controls, designed to help editors create the highest-quality productions. Edius Pro 3 is also included with Canopus’s line of Edius hardware and software editing solutions, including the new HDV offering, Edius NX for HDV.
Edius Pro 3 is available from Canopus and its authorized resellers and system integrators for a suggested retail price of $699. The new support for 720p YUV component out (24/25/30p framerates) will be available fourth quarter 2005. For more information, visit the company’s website at www.canopus.com.
