Visual Effects, News and Importance
Posted: November 30, 2005 at 12:32 pm, by Isaac
It’s been kind of a slow week for news, and I’ve been a little too busy to write up any tutorials, reviews, or articles, so here’s a quick summary of website I visit regularly. Vfxblog.com is a site maintained by Australian effects expert Ian Failes. Ian combs the webnet daily for news and articles about visual effects in recent and upcoming feature films, and frequently posts exclusive interviews with VFX technicians.
Over the last couple of days, vfxblog has posted links to the new issue of Cinefex (including a Peter Jackson interview), a number of articles from Film and Video magazine, a podcast about using moving cameras from Scott Squires’ blog, and the latest video production diary from King Kong.
I’m going to try not to turn this website into a purely effects and animation, but that is my background, and it is something that I find interesting. And regardless of how interesting or boring the latest whiz-bang effects are to most readers, even the basic and humble independent film can benefit from a little digital manipulation. Over the last ten years, special effects have gone from an expensive way to show things that can’t be filmed, to a more affordable way to present things that are merely cost-prohibitive.
And even the most technophobic of independent filmmakers should be aware of some of the new advancements that can add value to their final films without expanding their budgets too much. After all, some of the recently available technologies are the entire reason that we have a budding independent industry, and affordable equipment, so have a look through some more of the links at left.
BBC Video Standards
Posted: November 29, 2005 at 12:30 pm, by Isaac
I’m following up my last post on video scopes, signals, and levels with a link to some more information. For those of you who would like to learn more about video quality and broadcast standards, check out the BBC’s page on “policies, requirements, standards and best practice guidelines.” Available for download are PDFs and Word files on exactly what is required for BBC programming, as well as guides on widescreen and HD. Most television stations will have slightly differing lists of requirements, but BBC broadcast technicians are nothing short of legendary, and the Beeb’s rules are generally known as the highest industry standard around the world.
Admittedly, this data is less important to readers who are film snobs or hoping to avoid broadcast outlets, but anyone working with video of any form would do well to look over these lists. A rough working knowledge on what makes a quality video signal can be just as helpful (and easier to learn) as what makes a quality image. If you can’t afford to hire a video engineer who already knows this stuff, have a quick look. It can also be helpful to compare these stats to the specs of any video hardware you are planning to purchase. You can also read some more in-depth technical details on the Society of Motion Picture and Television Engineers website, but that is much heavier going.
An Introduction to Video Scopes
Posted: November 28, 2005 at 12:26 pm, by Isaac
There are a number of different types of video scopes, and various editing and compositing software packages will offer different diagnostic tools for analyzing images, but the underlying concepts are the same for measuring brightness and color. Below are examples of how standard NTSC color bars look when displayed on each scope.
The Waveform Monitor displays the luminance, or the black and white levels in your picture. Each white dot in the scope represents the luminance, or gray-value, of a pixel in your video image.
The display directly corresponds to the image from left to right. That is, looking left to right on the scope corresponds to looking left to right in the image. This means you can look at a scope and tell immediately where the dark and bright images are and roughly where they are located in the image itself.
Traditional waveform monitors are oscilloscopes configured for television monitoring, which measured the raw voltage of the video signal to check that all the pulses and scans of the signal are occurring at the proper times.
The main purpose of measuring the voltage was to make sure that the white levels didn’t exceed 100% or fall below 7.5%, as that would cause problems for the analog video signal. With digital video, top levels should not exceed 110%; signals that are too high will clip and blow out, and details that fall below black will disappear.
A well-exposed picture will be spread across all different levels, taking advantage of the entire range of the scope. A poorly exposed picture will tend to have the entire image squashed into a much smaller space. In post-production, the waveform monitor should be used like a histogram; keeping whites white and blacks black while the picture is adjusted.
The Vectorscope is another specialized oscilloscope, which measures color information, displaying saturation and hue. The closer a color is to the wheel’s center, the less saturated it is, and where it falls around the circle indicates which color it is. Brightness levels do not show up on the vectorscope.
In the same way that whites can be too bright, some colors, particularly reds and greens, can be too saturated and cause smearing and “bleeding” when displayed on television monitors. Being able to see exactly how saturated these colors are is helpful. Colors that fall outside the circle are not “broadcast legal” and colors outside the hexagon defined by the squares are not recommended.
The cross in the center of the circle represents zero saturation. Black and white values will appear here. Spaced around the circle are six (or on some scopes twelve) labeled squares representing the pure component colors of RGB and YU component colors of RGB and YUV video signals. When color bars are displayed, there should be six spots indicating the six main hues of the color bars, and these should end up inside the squares.
Of special interest is the diagonal line almost 45 degrees from the top, between red and yellow. This indicates flesh tone, which is a handy thing to remember when color-correcting footage and trying to keep skin tones properly balanced.
In Appreciation of HDforIndies.com
Posted: November 26, 2005 at 12:20 pm, by Isaac
I’d like to point all my readers to the site of my good buddy Mike Curtis. When I say he’s my buddy, we’ve really only exchanged a couple of emails, but the quality and comprehensiveness of his fantastic video and film tech website has made him an invaluable friend to me and pretty much everyone in the independent film industry. HD for Indies is the undisputed, number one, best source for news and information about the latest HD gear, specifically from a filmmaker’s perspective. In addition to the daily news posts, there’s an archive of 1600+ articles to search through, so it’s a good place to start.
I’m not a big believer in the “Apple is the Savior of Movies” gospel, but unlike a lot of tech writers, Mike actually practices what he preaches, and is currently starting up an Austin-based post facility for HD color correction and “sweetening.” For an introduction on where things currently are with HD filmmaking, DVguru.com recently posted an excellent interview with Mike, and here are parts one and two.
Lenses: P+S Technik Mini35 Review
Posted: November 19, 2005 at 12:21 pm, by Isaac
One of the reasons that video tape never looks quite like film is because of the lenses. As important as the actual film itself is, the image will only be as good as the lens it has been shot through. This isn’t to say that all video lenses are low-quality, but they certainly handle the image differently. The reason for this is that a lens for a film camera must present an image onto a 35mm wide piece of film. This is a big image, and it takes a big lens. Most professional video cameras have 2/3″ CCDs, which is quite a bit smaller. Cheaper cameras may have 1/3″ or 1/6″ CCDs, which require even smaller lenses.
Small lenses have several problems. For starters, they are difficult to manipulate precisely, and imperfections can be more obvious. The most obvious difference, however, is in the depth of field; or how much of the image is in focus. A film lens is larger, and has a larger aperture. The wider the iris is, the fuzzier the background will be when the foreground is in focus. A smaller video lens will have a much sharper image. However, it is difficult to simply put a film lens on a video camera; a complex adapter is needed.
DVXuser.com recently reviewed the Mini35, made by P+S Technik, which is a complete system for using 35mm lenses, matte boxes, filters, and tripod heads with a MiniDV camera such as the XL1 and the DVX1000. It works quite simply; the film lens projects and image onto ground glass plate, which the video camera sees. A variable-speed motor spins the plate to that less grain is visible. The whole setup is bolted onto a sleigh that turns that camera and lens into a complete unit.
The results are far more cinematic-looking, but there are a few drawbacks. For example, the weight and bulk of the adapter make it difficult and uncomfortable to shoot handheld, and a lot of light is needed to compensate for the ground glass. Also, the price tag is around $6000, but the Mini35 is the top of its game, and cheaper, similar solutions may be available.
Posted: November 19, 2005 at 12:18 pm, by Isaac
Following on my recommendations for lighting rigs, here is a series of tutorials on lighting. It was been written by Richard Harris, who is an animator and painter, so most of his examples explain how to recreate realistic lighting conditions in 3D and on canvas. That might be less useful to videographers who are looking for practical lighting solutions, but he does a good job of explaining the terminology, and has a number of examples of exactly what different lighting setups look like.