It can be hard enough to guide your project from conception to completion without introducing delays and technical issues that lessen the power and impact of your film, delays and issues that often can be easily avoided. To that end, test or calibration charts are invaluable tools for pre-production as well as production, and they are not just for rental houses and camera shops. Most available charts are designed for framing, resolution, and focus, and are suitable for use by equipment owners, "one-man bands" rental houses, and anyone entering production. In this article I will discuss the use of the above charts as well as color charts.
Now, while you might be happy to just whip out your camera and start shooting, there is a compelling reason to invest in understanding and shooting charts before production begins; especially when working with more than one camera, or when you are not the only person dealing with the material, that reason ends up being time.
Everybody Is on a Budget
We know that "time is money," but whether you are making films and video for a living or just as a creative outlet, there is only so much money you have for each project. More importantly there is only so much time that you can allot to each project—only so many hours in a day, and only so many days that you can spend shooting, editing, and finishing your project. Once you start shooting, anything you can do to reduce delays on set or location, as well as in post-production will not only save you money but afford you more time to explore your creativity. If you plan to release any of your work in a public setting, where you have little to no control over how it's displayed, then becoming familiar with and using a variety of charts is going to make your, and your audience's, experience so much better.
Before You Begin
Whether you are assembling a camera and lens package to own, or putting together a package to shoot a specific project, it is important to test the resolving power and frame coverage of your lenses, to make sure that you don't unknowingly switch between lenses that are noticeably sharper or softer within the same scene, unless that's your specific intent. So, testing the resolution and geometry of each lens as well as color and contrast can help you to choose the lenses that provide the least jarring transition when switching between lenses.
Resolution Charts
Resolution of lenses and optical systems are often evaluated in terms of line pairs per millimeter. The higher the number of line pairs, the greater the resolving power (sharpness) of the lens/optical system. Resolution charts such as this Spherical Lens Chart or the Mega Sharpness Box are often wall mounted, and the camera must be set up with the center of the lens at the same height as the center of the resolution chart. Examine the center, as well as the corners of the chart when you shoot to see how the resolution holds up over the entire frame. Also check the corners for vignetting (a darkening of the image around the edges), to ensure that your lens covers the entire shooting frame.
Framing
You would think that this would be a simple matter, but sadly it isn't. Even back when film reigned supreme, there were many standards, and now with digital and the plethora of sensor sizes, shooting and delivery formats, setting a frame before your production begins is more important than ever. Shoot the framing chart and distribute the framing video to your post-production team, so they can check their monitors, and the daily footage as it comes in, catching any potential issues early. Distribute it to your production crew, DIT, Sound Recordists, Video Village, etc., so they can mark their monitors with frame lines to watch for intrusions in the frame that should not be there.
Framing chart
With the differences in displays, it is important that you mark your monitors, from on-camera, to DIT, video village and playback (if you have that luxury) so that you can be sure that everyone is seeing the same image size and framing. It is extremely valuable to do this before you start shooting because pre-production time is relatively inexpensive when you just have a few cameras, monitors, and crew in a controlled environment, Compare that to trying to do it while on-set and the weather is bad, the sun is going down, you've got half a dozen actors, as well as hundreds of extras, a full crew (now getting paid double time), and you suddenly realize that the monitor you've been using has been set incorrectly, your lead characters heads are cut off, and the framing is bonkers and you get my point.
Perhaps that is a slight exaggeration, but once the cameras roll on principal photography, think of every issue as a potential snowball that becomes an avalanche to bury your production. You can, and should, shoot a framing chart with every camera you are going to use on a production with the proper lens and camera settings, or shoot perpendicular to a wall and use large arrows on the wall to define your frame. Use the arrows as well as tape or paper notes to indicate a desired aspect ratio, safe areas, a common top line for protecting different distribution formats, and visually leave any specific notes for the postproduction team. If you have space, adding in some siemens stars can give a quick focus check for the postproduction team's monitors. Make sure a copy of your filmed framing chart is sent to the editor so that they can make sure the footage lines up correctly in their system.
Anamorphic Chart
Anamorphic lenses are used in cinema to provide wide-screen images on a 4:3 film negative. This optical effect first arose to combat the rise of television, which was free to watch and severely cut into the movie theater attendance. Widescreen anamorphic films offered a visual experience that early television could not provide. Anamorphic lenses and attachments are extremely expensive and produce specific artifacts that over the years became part of the cinematic language. Anamorphic lenses and attachments for film and video squeeze the images horizontally, resulting in an unnaturally tall and thin output. But, when the image is screened, it is de-squeezed, restoring the natural appearance and wide field of view.
Set up and shoot this Anamorphic Chart with your lenses and the ellipse shape on the chart will become a perfect circle viewable through the viewfinder without the image needing to be de-squeezed, thus you can visually tell that all your lenses are and/or anamorphic adapters are providing a consistent squeeze ratio. In addition, the chart includes line-pair targets to show the lens's resolution. As a side note, if the ratio is slightly off from lens to lens, this chart can be used in electronic post to tweak each lens to match each other. There is a limit to how much can be tweaked without compromising your image, so if your lenses have a large variation in squeeze ratio, it is better to find out before your shoot and swap out for more consistent lenses. Also note that the chart is built to work with traditional 2x squeeze anamorphics that provide a 2.66:1 aspect ratio on sensors with a 1.33:1 aspect ratio, not the 1.3x, 1.5x, or 1.8x squeeze anamorphics that have entered the market in more recent years.
Focus Charts
Typically used during preproduction testing to check the calibration of lens markings for pulling focus in the field, these charts are also useful on set when getting critical focus, especially when shooting with extremely shallow depth of field. Siemens Stars are useful focus tools for setting focus in dim, or low-contrast images and can be found in a variety of sizes. Another use for the stars is quickly checking and setting the back focus on lenses with back focus adjustments. There is a set of smaller charts useful for location work.
Color Calibration Charts
Not to be forgotten are color and chip charts. A variety of these are available across the production world, ranging from Kodak to Macbeth. It can be extremely important to have a standard color pattern that you can capture with multiple cameras that are going to be intercut together, especially when using cameras with different sensors and color science. Many of the available postproduction software packages these days have a "match color" feature that can be fairly accurate and get you most of the way there. Shoot the color chart with each camera and use the color match function in the software to equalize the footage, then do your final color tweaks. Check your software to see which color chart it works with or check with your colorist to see which chart they prefer.
It takes a little extra time and planning, but in the end the costs of using calibration charts are negligible when compared to the potential costs of not taking advantage of them. Plus, there is the added benefit of having a better understanding of the capabilities and unique characteristics of each of your lenses and cameras, offering you more control, allowing you to take more risks and pushing the boundaries of your creative process.
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