Color Correction and Sky Replacement

I’d like to follow up yesterday’s post by giving a few examples of ways that simple and cheap digital effects can improve the average low-budget film. The most obvious and probably the most useful tool in post production is digital color correction. Almost every software-based non-linear editor can adjust the hue, saturation, and levels of any video clip. This is important for those filmmakers shooting on video who would like to emulate, or at least simulate, the warmth and depth of film.

And as handy as those simple controls are, compositing programs like After Effects and Shake can accomplish much more. Individual parts of a scene can by isolated and tweaked. Sharpening or blurring can emphasize or obscure certain details. Minor camera shakes can be fixed. Glows and blooms can be added to highlights. Specific colors can even be altered, turning green spring foliage into a warm autumnal environment.

But sometimes changing what already exists isn’t enough, and new image data must be added. Video captures much less color depth than film, so when the camera is exposed for an actor’s face, the sky behind him will probably be completely blown out. With the right equipment and good polarizing filters, some of the sky’s color may be salvageable, but with highly compressed 8-bit DV video, it’s more likely to be pure white. This is where sky replacement can come in.

For years now, Hollywood effects houses have been adding new sky and cloud elements to locked-off plates when the images need more dramatic kick, or they needed to simulate weather that wasn’t available on the set. However, this is now a very simple procedure for anyone with a basic working knowledge of almost any compositing package, and skies can now be tracked to moving and even hand-held shots. Andrew Kramer has an excellent tutorial on how this is done.

Adding an image as simple as a blue sky or a few clouds can instantly make an image much richer and more filmic, and with a little planning on the set, you can shoot images that will integrate with dramatic sunsets and moving clouds, as shown below:

Visual Effects, News and Importance

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

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

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.

In Appreciation of HDforIndies.com

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

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.

Lighting Breakdown

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.

Itchy-Animation.co.uk.

Lighting Rigs for Film and Video

It’s been a while since I dug into my e-mailbox for questions, and I apologize. First on my list is a query from a team of brothers who are interested in investing in a lighting kit for their production company. At the moment, they are shooting most of their projects of DV, but their long-term plans involve feature projects shot on film. They wrote to ask whether the lighting gear that their video projects required would still be usable on their films.

Fortunately, film cameras and video cameras have similar technical lighting requirements. If you buy a simple lighting rig for video use, those lights will be very suitable for lighting a 35mm film shoot (depending on the film stock and lenses that you may be using). The only real differences between the two formats are than they will generally have different styles of lighting. If you have to light an entire set rather than one interviewee, you will obviously need more lights. However, the color temperature and intensity of a standard halogen 650 watt light are ideal for film.

Owning your own lighting kit is very helpful, for a number of reasons. Firstly, if you have the gear, you have the freedom to experiment with it and practice different styles. Secondly, it lets you be more flexible in shooting, and you can jump onto projects quickly without having to organize gear. Unfortunately, professional lights and light stands are not cheap. Fortunately, they are pretty sturdy, so if you can find used lights in reasonable condition, they should be more than adequate. Starting videographers shouldn’t need anything much more complex than a simple three-point lighting rig.

This will be a key light, which is the main light that illuminates the subject. Then there is a fill light, which is softer, and placed on the opposite side as the key light to fill in the shadows. Then, you have the kicker, or backlight, which sits behind the subject and just puts a little edge-lighting unto the subject. The key and fill lights should be either 650 watts, or 1000 watts. These are the two main sizes of light used in video – film shoots may require much larger lights for larger film sets or location shooting.

The kicker light, on the other hand, doesn’t need to be anything that special. A regular hardware store clamp lamp with a 75w or 100w is all that is needed for backlighting. As you experiment with lighting techniques, you’ll have better ideas of how to use diffusion, colored gels, natural sunlight, reflected or “bounce” light to get the results that you want.

Shooting Ratios and Film Takes

Today’s question comes from my friend Luke, formerly a brilliant animator, production and conceptual artist, currently a brilliant portrait painter. He writes, “Working as a portrait artist has taught me that to get just one, really successful image, it usually takes about 40 shots. Film is even more complicated — so how many “takes” does one need for the average scene? Is there an industry standard for wastefulness?”

The answer is, no; not really. Every director will have his own style of dealing with actors, and his own expectations of how many takes he will want to get what he is looking for. Some actors are more experienced and better at understanding the director’s vision. Some directors will have multiple cameras on set, which means more film will be used (even if fewer takes are required). If the director shoots long takes, there is a greater chance that actors will make a mistake and they will need to be re-shot. If he shoots short takes, then more film is wasted on the “slate” material that will be edited from around each take.

There are too many variables to really make a generalization of what an industry standard might be. However, when you begin to plan a feature, you must have a reasonably accurate idea of how much film stock you will need to buy. This is tricky, but it’s not to difficult to calculate a rough estimate. Let’s assume that you are shooting a low-budget, independent 90-minute feature. Independent means you don’t have studio connections to negotiate a great deal with the supplier, and you don’t have the budget to buy any more than your bare minimum.

A 35mm camera shoots at 24 frames per second, which amounts to just over one and a half feet per second (film is measured in feet). You can find a number of timecode calculators on the internet that will convert between frames and feet precisely, and my favorite is WTCC II. Your ninety-minute finished film print will be exactly 8,100 feet long. If you have a six-to-one shooting ratio, which is cutting it pretty tight, that means you’ll need 48,600 feet of film stock to shoot your movie.

At some point, I should write an article on how to buy film, but here’s a quick summary. The two main manufacturers are Fuji and Kodak. Kodak donates raw film stock to film schools, so most beginning cinematographers will insist on shooting the Kodak film that they are familiar with. However, Fuji film is generally cheaper (but there are different types and speeds of film stock where that may differ). It comes in cans of different lengths; long reels for large magazines for dolly and tripod shots, and shorter, lighter lengths for handheld and Steadicam magazines.

The Mechanics of Storyboarding

Something that I always emphasize, to anyone who will listen, is the importance of planning. It’s impossible to create a good film on schedule and budget unless you have an accurate schedule and budget. It’s equally impossible to edit a good film out of poorly planned and poorly shot footage. To plan your shots well, you need a storyboard that covers all your shots. Easier said than done. So, today’s mailbag question is, “Is there software or a template you would recommend for storyboarding a movie?”

I can’t think of any software specifically designed for storyboarding a film… all you need to create are simple sketches, so any basic paint program will work just fine (although I highly recommend Wacom tablets to draw with). I do almost all of my storyboarding on paper. I print out a stack of templates, and then scan them back into the computer when I am finished. My template look like this: a 4:3 box for me to draw in, a small box in its upper right hand corner for the shot number, and a small thin box underneath it; just enough for a few lines describing action, camera move, or dialog.

How many of these panels you print onto a piece of paper depends entirely on how large you want to draw. I myself am a very poor artist, so I make very small panels, and I only draw little stick figures in them. Stick figures with noses; so I can tell which way they are looking. Stick figures and arrows showing the camera movements are pretty much all that you need. A little description under each panel will help them make sense if your art is as bad as mine, and shot numbers are imperative to keep things in order. If any shot is complicated enough that it requires multiple panels, name them 14a, 14b, 14c, etc.

Once you have a scene storyboarded, and the panels have been scanned in and separated into individual files, you can load them into Final Cut Pro or Premiere or whatever editing program you use. Then you can lengthen and shorten shots to fit your scratch track (which will be you reading your script with the rough pacing that you want), and create a timed animatic of that sequence. Once you have your whole film storyboarded and cut to a scratch track, you basically have your whole film finished. You can see what takes too long, where you need more shots, and where your pacing is right. Now you can stick your storyboard pages into a folder and go out and shoot a film that you know will work.

This kind of planning takes time, but it is imperative for well-ordered films – particularly for young directors who don’t have a lot of experience yet. Some animatics are cut from video-taped rehearsals with the actors, but unless you fully block the action of the scenes out on the actual sets that you will be using for the final shoot, you won’t have a fully developed idea of your camera angles and cutting, and you’ll still need a proper storyboard that takes these thing into account.