VR TOOLS YOU CAN USE - GREENSCREEN The Shot That Never Was. by Pat St. Clair
[Ed: Pat St. Clair has kindly agreed to contribute a regular column to VRMag; this is his first in the series. We’re thrilled to have a photographer of his skill and knowledge onboard and hope readers will benefit from his expertise and thoughtful advice. ]
Those of us producing 360º panoramas, object movies and full-featured interactive media have to be somewhat multi-disciplined. At the very least we have to be part photographer and part computer-geek. Personally, I choose to be the best photographer I can be and limp along on the computer-geek side of it. I usually have to beg help to successfully get something online.
Many others choose to control every step along the way from image capture to authoring elaborate interactive titles with original audio embedded in state-of-the-art Live Stage Pro animated extravaganzas (I don’t know where they get the time, these people must not have kids!).
My point is, wherever you fall in this range of skill sets, you are constantly solicited to buy new tools to incorporate into your workflow . . . to jump on another learning curve in order to expand your capabilities and improve the quality of your work. Trouble is, there are so many potential cool things out there, it’s hard to find the time to investigate them all.
Of the many directions you might explore, let me encourage you to take a look at greenscreening. Whatever path has brought you to VR production (photographer, computer-geek, media producer, web designer, etc), greenscreening is something you should know at least a little about.
As with most tools, greenscreen software varies greatly in features, complexity and price. Typically, less expensive software gives you less control over the process by relying more on presets and defaults. The learning curve is gentle, but your choices are limited, and it can’t handle every situation. The more expensive software typically gives you incredible control over the process with lots of expert user tools, but at a higher cost and with a steeper learning curve. I’ve looked at several of the greenscreen tools, downloaded demo versions of some, and I personally have settled on one called Primatte. I like Primatte because I personally consider it to be a good mix of features and ease of use, yet it doesn’t break the bank. My need for greenscreening is occasional, not an everyday thing. Yet, when I need it, I really need it. Primatte fills that need for me.
If you do a search online on greenscreen, you’ll find a variety of products … spend some time and find the product that fits your particular needs. Then download a demo version and try it out.
Bluescreen, greenscreen, chromakey and color key all relate to a compositing process where a known color in one image is made transparent to reveal the corresponding portion of a second image. (Imagine a layered image . . . now erase through a portion of the top image to reveal that portion of the bottom image . . . that’s the idea). It can be used in stills, film & video . . . the stereotypical use is the TV weather person who appears to be standing against a large weather map. In reality, he/she is standing against a greenscreen.
In its simplest form, the process has two components to it (and for this explanation, I’ll be referring to a still photo created with greenscreen techniques):
1. Photograph using a “known” background that is different from all other colors in your shot. This might be a paper backdrop, a special fabric, or even a specific color paint formulated for this purpose. Typically, these products are offered in a vibrant blue color or a vibrant green color (hence the terms bluescreen and greenscreen). Select the one that is farthest from any colors in your subject matter.
2. After photographing your subject against the bluescreen or greenscreen background, you need software that recognizes the background color as the color you wish to be “transparent” to allow the second image to show through all areas of the scene that are that color -- again, this is an overly simplified explanation.
Why might you want to use such a process? I offer four uses I have made of the greenscreen technique as my answer to that question:
1. Product Photography. Shooting products against a greenscreen enables compositing that product against a variety of backgrounds over the lifetime of that product photo. Here is a product photo composited against a graphic background using Primatte:
As an added bonus, I’m able to save out a mask that Primatte creates to facilitate the process. So, I could use this technique as a way to create silhouettes for a product catalog.
NOTE: In this particular use, I used the mask created by Primatte to enable adding a drop shadow after the fact.
2. Portraiture. I once had the assignment to shoot company portraits for one company over a period of years. Each new employee would have a portrait done and the background had to be consistent with all previous portraits. The desired background was striated light splashing across a gray gradient - a hard background to consistently match. After creating the background for the first shoot, I used greenscreen technology for every subsequent shoot, and backgrounds matched exactly over a six year stretch. I will say that blond hair sometimes gets confused in the color-key process, so occasionally I shot against a bluescreen.
3. QTVR Object Movies. For many subjects, greenscreen can be a real time saver in VR object movie workflow in that it can greatly simplify the masking process.
4. And finally, THE SHOT THAT NEVER WAS. This assignment put greenscreen to the test as far as I was concerned. A number of years ago (actually in the film days), I was hired to create a group portrait of four executives. Problem was, their schedules did not offer a time when they were all in the same state much less available for a group portrait. Yet the shot was key to a larger communications project. So I offered to do it using greenscreen technology.
I started by doing a group shot with four other people in it to serve as a compositional reference. I then shot each key individual separately over a period of days against a greenscreen. First was the man on the far left, and I started with a medium format Polaroid image. Then I shot a roll of 35mm film with him smiling, not smiling, with jacket on, with jacket off, etc. It took no more than 10 minutes. Next was the man sitting. I shot the medium format Polaroid and cut ‘n pasted it to the first Polaroid. Then I shot a roll of 35mm film, again - smiling, not smiling, etc, etc. Then the last two were added (one at a time), Polaroid first, followed by a roll of film capturing some variations in tone and dress. At the end of it, I had a Polaroid preview image that consisted of four individual Polaroids cut ‘n pasted together to make a quasi-preview of the group shot’s composition.
Because each was shot against a greenscreen, there was no background setting. I exported a frame from a VR pan I had shot previously in the firm’s library. The table was created by a graphic artist (it didn’t exist), as was appropriate shading within the image to give the dimensional clues that would be there if the four people had actually been standing together.
Hence . . . THE SHOT THAT NEVER WAS!
Not only did the technique succeed in overcoming logistics roadblocks, but each individual could look his/her best within a group photo.
Here is the final composite photo:
And here is a key illustration of how it was done:
(my thanks to Strapp Studio for the artistry provided to complete this scene.)
About the author: Pat St. Clair has a bachelor’s degree in marketing from Miami University (O), 1971, and a bachelor’s degree in professional photography from the Rochester Institute of Technology, 1979; he has been photographing commercially since 1978. St. Clair serves a corporate clientele that includes agencies of all sizes as well as direct corporate clients such as Eastman Kodak Company, Palm, Xerox, Hewlett-Packard, 3Com, DaimlerChrysler, ExxonMobil, Microwave Data Systems and more. He was an early adopter of digital technology and has worked with Eastman Kodak Company on digital capture projects and digital image quality issues for the last eleven years. He has worked with QuickTime VR since 1994, is a charter member of the IQTVRA (now the IVRPA), and was a speaker at the first four VR Summits in Boulder, CO, Washington, DC, Sedona, AZ and Savannah, GA. He is onboard to speak again at the 2006 VR Summit.
He owns and operates St. Clair Photo-Imaging in Rochester, NY. More about Pat St. Clair and his work can be found at St. Clair Photoimaging
[Ed: Pat St. Clair has kindly agreed to contribute a regular column to VRMag; this is his first in the series. We’re thrilled to have a photographer of his skill and knowledge onboard and hope readers will benefit from his expertise and thoughtful advice. ]
