Protecting Your Vision On Film With Frame Leaders and Chip Charts
by Mark Woods TV and the Cinematographer
Working in TV presents some special "opportunities" for the director of photography to preserve his vision. TV shows are posted electronically, yet the telecine machines and bays have no perfs as a reference, unlike an optical printer or work print. The electronic machines also don't have printer lights, and, although Kodak has developed a system of telecine lights, it's not in general use and adds a slight amount of time to the transfer if the bay is set up to use it and the colorist is trained for it. With that said, there are two basic ways the director of photography can protect his vision no matter what format he's working with.
TV Formats Represented on The Ground Glass
If you look at the ground glass drawings Tak Miyagishima at Panavision has kindly provided, you will see the obvious: when shooting 4x3 (1:33) and protecting for 16x9 (1:78) part of the image is either lost or revealed. In all of the formats, except the Paramount format, the show is filmed in 4x3 (1:33) and the 16x9 (1:78) "sides" are protected for future HD presentation. A Paramount format has common sides and top, but loses a portion of the bottom of the composition when the image is presented in 16x9 (1:78) after a tilt and scan. All of these formats have supporters and detractors and present compositional challenges for the operators. What directors of photography need to be aware of is how to indicate to the postproduction house, and future postproduction facilities, what the show's format was when it was filmed. The communication today with the postproduction supervisor isn't enough since the archival aspects of film approaches 100 years (the half-life of videotape is 15 years).
What's Common With All Formats?
When filming a TV show using one of the formats that centers 4x3 (1:33) with a common top and bottom while "protecting" the sides for 16x9 (1:78), the ground glass should have TV Transmitted and TV Safe indicated. If the ground glass only indicates TV Transmitted, and those line indicators are used for framing, when the 16x9 (1:78) is aired in the future the sides will be lost. Let me explain. The postproduction facilities can make 4x3 (1:33) images work using the TV Transmitted lines on the ground glass. This is a simple matter of reducing the image slightly during telecine by using the remaining part of the image above and below the transmitted area. This doesn't seem like a big deal, and for now it isn't. The problem is in the future when the show is presented in 16x9 (1:78). If the image is reduced to make up for the fact that the show was shot using the TV Transmitted lines for framing, part of the image on the sides, and top and bottom, of the 16x9 (1:78) will be lost. The same is true if part of the image is used from above and below the TV transmitted lines, the ratio of width to height has been changed, and something will be lost. In other words, if the image uses more of the height, it must have more width. Of course this isn't possible since the edges of the 16x9 (1:78) frame is set and can't be expanded. The only way the 16x9 (1:78) can be projected is to lose part of the top or bottom, or both, in order to fill the 16x9 (1:78) frame. The director of photography needs to understand what TV Transmitted and TV Safe indicate and to communicate it to the operators and colorists. If only one frame line is desired, then that frame line should indicate TV Safe, and the frame leader should also indicate that.
Common "TV Safe" Ground Glass Indications
Take a moment to look at the drawings of the Ground Glasses. All of them indicate the Full Aperture, the TV Transmitted area, and the TV Safe area. Again, it may appear that you could use the TV Transmitted area for framing because modern TVs transmit the whole image, but that would also be a mistake. The TV manufacturers have at least 10% tolerance in the electronics of their receivers. This tolerance is the difference between TV Transmitted and TV Safe. The part of the image that is lost could be on any side, or all sides of the image. You can quickly understand why the use of the TV Transmitted for framing is a problem. Again, I know of directors of photography who do use the TV Transmitted indicators for their frame line and have no problems now. But look again at the Ground Glass Drawings for the common top and common bottom formats particularly the 4-perf format. Note the image area above and below the 4x3 (1:33) TV Transmitted lines. It would appear that this is wasted negative and should be used in filming the show. If the show is only going to be viewed in 4x3 (1:33), that would be correct. Again, the problem arises on the sides of 16x9 (1:78). If the TV Transmitted lines are used in framing for 4x3 (1:33), there is little or no information left for 16x9 (1:78) sides. It is this future application we are being asked to protect. The more height used, the more width is necessary.
Pedestal Film Cameras/Multi-Camera Productions & Ground Glasses
In researching this article, I visited a set that uses 3-perf pedestal cameras. Panavision has modified their Panaflex cameras with an optical block that splits the image's exposure, allowing 70% to expose the film and 30% to be used by the video tap. There is no eyepiece on the camera. There also isn't a "ground glass" in the sense we think of one. But a scribed glass blue filter indicating TV Transmitted and TV Safe is inserted in the optical path, and works with the video tap in the same manner as a ground glass works with an eyepiece. The lines are calibrated to the camera in the same way the ground glass is in a normal camera. In that sense, the lines are as accurate as ground glasses are on a camera with an eyepiece, only the method of achieving the indicator lines is different. In cameras where these lines are electronically indicated there probably would be a problem, but I'm not aware of a film camera that uses an electronic indicator as opposed to an optical/mechanical indicator. On multi-camera film shoots where the operator views the scene through the eyepiece, there shouldn't be any problem with the ground glasses being different if the cameras are all from a reputable rental house, like Panavision, Clairmont, Otto Nemenz, etc. The other stipulation is that all the ground glasses have the same indications. In Super 35mm (2.40:1), the different frame indicators can be scribed in different locations within the full aperture. In multi-camera productions, the director of photography needs to have all the cameras' ground glasses match in format and what is indicated on the ground glass. Minimally, this would be TV Transmitted and TV Safe. There should be no exceptions. More about this later in the Colorist section.
Frame Leaders & Why They're Important
From what I've said, you can see why shooting a frame leader is important. The information on the frame leader establishes all edges of the operator's compositions. Without this information, the electronic postproduction facilities can't accurately position the image for 4x3 (1:33) TV, much less 16x9 (1:78) HDTV. The headroom will never be what the operator composed; the sides will have either too much or too little information. The work of the director of photography is compromised beyond the "shoot for 4x3 (1:33) and protect for 16x9 (1:78)." I've included a frame chart from Panavision that indicates 4x3 (1.33) TV Safe and 16x9 (1.78) Protected. One of the issues I've heard from a number of postproduction houses is the desire to use the common top and common bottom while protecting the sides. The more accurate approach is to use a common top and bottom TV Safe while protecting the sides for 16x9 (1:78) TV Safe. The common top and bottom TV Safe is a more accurate indicator of what the final viewer sees, and better insures the compositions will remain true to what the director of photography, with the camera operators, actually filmed.
Two Ways to Film a Frame Leader
The first approach to filming a frame leader is to find an accurate frame leader like the one published here in International Photographer Magazine, available free to our members. If the frame leader is spray mounted to a piece of show card it will simplify filming and make it easier to keep in good shape. By the way, don't enlarge or reduce the chart, since photocopying tends to change the height to width ratio. When filming the chart, it must be parallel to the film plane and perpendicular to the optical axis. Use a 50mm lens for 35mm format (a 25mm lens for 16mm). The indicator lines on the chart need to be lined up with the correct indicator lines on the ground glass. For example, the TV Safe indicators on the ground glass are placed over the TV Safe lines on the chart. The TV Transmitted lines on the chart are lined up with the TV Transmitted lines on the ground glass. Once this is done, the framing chart is exposed and after the film is processed, the transfer house should be given the framing leader with the instructions that these lines are accurate to the ground glass on the camera, and should be used for all transfers for the show.
Another way to film a frame leader is to use the camera as a projector and project (or rotoscope) the camera's ground glass. (In the early days of film, cameras often did double duty: after the film was processed, the camera worked as the projector.) To do this, my 1st AC, Mike Bratkowski, puts a piece of foam core about 4 feet in front of the lens, parallel to the film plane. He then tilts up the eyepiece and focuses and centers a Tweenie, or another small bright light source, into the eyepiece. The light travels though the eyepiece optics, through the ground glass, reflects off the mirror, and he focuses the ground glass's image through the 50mm lens onto the foam core. In a dim room, the image is clear and absolutely accurate to the ground glass in the camera. He then uses 1/2" paper tape to clearly label the different line indicators and which each indicates (i.e., TV Safe, TV Transmitted). Once he has done all this, he then resets the light to now film the chart (with no hot spots). We've used this method for a number of years with great results. The line indicators on the ground glass match the frame leader we turn into the lab and the post production supervisor.
The Frame Leader = Telecine's Ground Glass
I really can't emphasize how important it is to film an accurate frame leader for the transfer house indicating TV Safe on the film. Since there is no "ground glass" or a standard image size for the telecine machines, the frame leader works as the telecine's ground glass that matches the camera's ground glass. This is a one-to-one relationship that insures correct framing and positioning of the image. Once the director of photography has shot a framing leader and given it to the transfer house, it's important for him to communicate with the operator what each line on the ground glass indicates, and the importance of each. If only one indication is desired for each format, that line indicator should be TV Safe. The frame leader should be shot with the TV Safe lines coinciding with the TV Safe lines on the ground glass. In this situation, the TV Transmitted lines could be on the frame leader while not being on the ground glass. The important aspect on all of this is to understand the ground glass line indicators, and to use them accurately.
The Colorist and "Loops"
In preparing this article I spoke with quite a few colorists about an ideal "wish list." "Give me a loop with the camera's ground glass frame lines," was virtually the first thing they all said. It was a unanimous desire for the directors of photography to provide a framing leader long enough to be spliced into a continuous loop for their telecine machines. On that framing loop they wanted the line indicators labeled either TV Safe or TV Transmitted-but definitely labeled. If only one indicator was on the film, the majority of the colorists said they would prefer it to be the TV Safe lines. If the TV Transmitted lines were used, then the colorists would match those indicator lines with the indicator lines on the in house framing loop.
Some of the colorists also suggested that all cameras on multi-camera productions film a framing leader. All of these colorists said that when the cameras were set up correctly there was virtually no image shift. But where the framing leader was absolutely necessary in multi-camera shows was to reaffirm that the ground glass was not only correct, but correctly seated in the camera. Mistakes do happen. There is also the possibility that happens on 3-perf shows when a 4-perf camera is brought in and must be used. If a framing leader isn't shot, then correct composition can't be assured at the telecine. Another request by a few colorists was to include the center crosshairs on the framing leader. The reason being that if all else failed, at least the colorist could position the center of the frame accurately, and position the frame edges relative to that indicator. Another argument for this is that if the framing leader isn't shot absolutely perpendicular to the lens and accurately centered, the cross hairs indicate the center and any keystoning problem will solved.
Color Charts, Gray Cards, and Chip Charts
Another unanimous agreement was regarding some type of chart to indicate the density and color of the negative. The colorists wanted something to indicate "ground zero" for them to begin to color the show. Just as a frame leader/loop indicates the composition, a chart-when exposed correctly-indicates the colors and textures the director of photography strives to create. Most colorists suggested the director of photography use a gray card of any type. The second most requested item to be shot was a Macbeth or other well-known color chart. Last on the list was for the director of photography to put his/her face in the shot as a skin tone reference along with the color charts. The only problem some of the colorists pointed out is that the directors of photography usually don't go into makeup before being shot, and they take less time to photograph themselves than they do the stars of the show.
The colorists split on filming the chart with diffusion, but they all agreed that the charts should be shot in neutral light, i.e. 3200° K light for Tungsten film, and 5500° K for daylight film. If the director of photography works in a stage where the average lighting instrument is about 3000° K, then the chart should be shot in that light. The key thought on this matter was that the chart should be filmed in light the director of photography feels is neutral in relation to the set s/he is filming. The chart should be filmed not only in the neutral light, but before any color effects filters are added and without any effects lighting on the chart. There was some suggestion that the chart be filmed in front of the set with the effect lighting (e.g., a night effect) lighted behind it so the colorist can see what the director of photography has created. This also means that the chart needs to be filmed at the same stop as the set is lighted for the effect to be perceived correctly.
Another issue some of the colorists brought up was to use the correct lens to film the charts. The ideal lens is a 50mm prime or zoom setting. This may seem a bit obsessive, but if you ask any optical engineer, s/he will support the colorists. On the longer lenses there is slight fall off at the edges, and with most zoom lenses (particularly the older designs) the T/stop also is less than is indicated on the lens. This effect is what's called "port-holing" and is particularly noticeable on video zoom lenses wide open and zoomed to telephoto. You can understand that a director of photography can take great care to light a chart correctly and have it all undone by zooming in the lens to fill the frame with the chart.
Finally, most colorists wanted the size of the chart to be at least two-thirds the size of the frame, if not filling the whole frame. Although they can isolate the chart, they feel the bigger the chart the better indicator it is, and speeds up their work.
The Transition from TV to DTV
During this time of transition from analog TV to Digital TV, and the change in format from 4x3 (1:33) to 16x9 (1:78), and other emerging formats, the director of photography is confronted with problems in composition. The individual cinematographers must solve these compositional problems, but filming a frame leader can protect the final frame s/he films. It doesn't matter whether the director of photography films in 4x3 (1:33) and protects the sides, or has a common top and clips the bottom for 16x9 (1:78), or if the 4x3 (1:33) frame is extracted from an electronic anamorphic 16x9 (1:78), the TV Safe lines will indicate the frame the director of photography composed his image in. As the electronic standards continue to evolve, the film can still be correctly transferred in the future to new electronic mediums with the use of a frame leader and a correctly exposed chart.
Note: If you need a larger size of the format chart, contact the camera company you intend to use.