Tuesday, March 1, 2011

The appearance of a Flamingo

flamingo group

Once upon a time, a day came when the management at Xerox PARC decided to hold elaborate Open Lab events to share our knowledge and achievements in pursuit of synergies. In the color project we had just finished building a research lab, and our director instructed us to better have a good demo in the Gray Lab, justifying is construction.

In fact, we had achieved quite a bit of notoriety, because we had it painted in gray, which was taken as a joke by our colleagues, who expected us building a colorful room. We even had it painted twice, because the first time, when we instructed the painting company to add pure black to white base and nothing else because we needed a spectrally flat color, they thought they were smarter than us and mixed a multitude of pigments to match the gray Munsell Sheet of Color we gave them as the standard.

When they called us upon finishing their job, their boss proudly held the Munsell Sheet against the wall, but we could see immediately that something was fishy, because the wall had a different color where it was hit by the light from the hallway (the lamps in the room were D50 simulators). We simply showed them their spectrum and they had to repaint the lab at their expense.

Other than the instruments and display monitors, the lab was completely bare, as to avoid contaminating the retina during psychophysics experiments. On the side we had also a small room completely painted in black with a spectroradiometer for the measurements. All lamps were D50, so we did not have to wait to adapt our visual system, and could reset it anytime by staring at a wall.

The announcement of the Open Lab event came with a big surprise: all the other team members would be on sabbatical or vacation that week, so I would have to set up the demo all by myself, including dealing with the crowd.

After some reflection, I concluded this was an impossible task, because all the other demos were very high concept. I decided to instead shoot a video in the lab and then just put in the door to the lab a cart with a big TV and a U-matic tape player. The question now was what experiment could I tape to demonstrate the need for a gray lab?

Chilean flamingoOne Sunday I surveyed the offices of my colleagues working in graphics and imaging, in search of an error possibly due to inaccurate color evaluation. Of course each office had pictures of Utah teapots showing off the occupant's algorithms, but I noticed that images of flamingos were quite common. I was amazed all these flamingos were of a vivid pink, unlike the vermilion I remembered from a zoo visit when I was a child.

So I thought I drive to Marine World/Africa U.S.A., which had just moved from Redwood City (now the site of Oracle) to Vallejo, get a flamingo feather, measure it, and achieve a perfectly matching reproduction on our monitors and printers, showing off the importance of chromatic adaptation and cross-device color reproduction.

My plan was to keep a professional Betacam in my office and just opportunistically record material, so I could make up a story at the end depending on what I was able to gather. When I showed the first drafts to my colleagues, they educated me that when Americans think of flamingos, they do not think of the bird at all, but instead they think of pink plastic lawn flamingos.

Well, so much for a naive boy from the Alps. There was not enough time for a different demo, so I stared at my hours of video sequences and made up this movie:

[If there is a problem with the above stream or you have a slow connection, you can download the movie from this link. If you stream from this link, there will be a buffering delay due to the slow connection.]

Unfortunately, the original U-matic cassette is no longer available, and my VHS copy is all gummed up. Unlike U-matic, VHS does not have SMPTE time code and the signal bandwidth is very narrow, so it took me 2 months of conditioning the tape and attempting replays, until I got most of the frames.

I would have loved to have Peter Schnorf's digital video editor having lost video frame protection, because I would just have run the digitization process a few times and the system would assemble the complete video.

I used a semiprofessional VHS player and first split the signal in separate luma and chroma components. I then adjusted each signal to fill its gamut and after analog-to-digital conversion denoised each signal. Since the signal is pretty bad, I did not try to do any enhancements, as they would amplify the defects: I simply transformed the digital video stream into MPEG-4 using Quicktime.

In the VHS device gamut of the YIQ color space, very little of the bandwidth is allocated to the magenta region, therefore the flamingos look terrible in the movie, washed out and like followed by a ghost.

An now a lame flamingo joke: Why do flamingos stand on one leg?

Digital Palette

If they would lift also the other leg, they would fall over.