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Saturday, March 26, 2011

••◊ Forget Megapixels. Think Gigapixels.

I received an email today from one of the local photography groups that I belong to. The email's author mentioned his upload of a Gigapixel panorama made up of over 1400 photographs. Holy cow! I thought my camera had more than enough resolution at 21 Megapixels. I've created 100 Megapixel panoramas, but those are pretty run-of-the-mill common. Gigapixels, huh? On the web... Had to check it out.

The web site is called gigapan.org. Some of the most popular panoramas are here. They include President Obama's inaugural address, A Farewell to King Bladud's Pigs, The Golden Gate Bridge, the Burning Man 2006 Waffle, and a South Pole 360 Degree Panorama. Unlike most photographs this allows you to truly explore the photograph. You never know what you'll find. Also brings up the new world of privacy considering they were able to crop out a woman sitting at a hotel pool in a bikini in Dubai from a couple miles away using a 44 Gigapixel image. Your mother was right. Always wear clean underwear.

Saturday, March 19, 2011

••◊ 5D mark II in camera color correction

I had a thought the other day. Since the 5Dm2 codec is so fragile, why can't I just create a custom picture style that gets a little closer to final color correction? At the heart of all Hollywood color corrections are two tweaks. First, saturating skin tones and playing with lightness of skin - to make everyone have that freshly tanned at the beach look. Two, drive the backgrounds toward the complement of skin color (aqua? turquoise?). Unfortunately the Canon Picture Style Editor doesn't quite give you the flexibility of a light/mid/shadow HSL color correction, but it can do a little bit to get you there.

The first step for me was developing something that approximated skin color and also the complement color. The lazy man's way of doing this is to open up Synthetic Aperture's Color Finesse in After Effects. All I had to do was tweak a solid color until it matched the standard skin tone line on the vectorscope. Easy. Then it was a matter of taking that same color and rotating the hue down to the complement line. At each point I recorded an RGB value of the solid color.

Next, we take those RGB values and input them into the Canon Picture Style Editor application. Turn up the saturation on the skin tones and the background. It helps if the talent is lit with a slightly tungsten light in the first place so the background is already kind of green-ish blue. Below you'll see a picture with the before/after tweaks (click on picture to enlarge, as usual). Notice that Brooklyn is much more tan looking now and the background is more saturated toward the green-blue complement color of skin with just two color correction points. The picture was white balanced using her shirt.

So what's the downside here? Well, typically in Hollywood films the shadows are shifted from neutral toward the green/blue color. The Canon Picture Style Editor software doesn't really give you that choice because it doesn't do lightness specific tweaks, nor shifts from neutral to a color. However, what I did is limit the green/blue adjustment mainly to the desaturated colors so it doesn't drift too far into items more fully lit in the foreground (likely to be more saturated).

This clearly doesn't work as well as true color correction, but it is a low budget technique to possibly pre-color correct footage from the 5Dm2 when used properly. Just be prepared to live with the cooked in results.

Saturday, March 5, 2011

••◊ Carnevale!

This weekend San Diego's Little Italy section of the city celebrated Carnevale! The exclamation point somehow seemed necessary. We all know that most Italians have a genetically dominant trait that doesn't allow them to speak without using their hands so the exclamation point is a reasonable emphasis substitute.

From Wikipedia...

"Carnival is a festive season which occurs immediately before Lent; the main events are usually during February. Carnival typically involves a public celebration or parade combining some elements of a circus, mask and public street party. People often dress up or masquerade during the celebrations, which mark an overturning of daily life."

From photog...

"An excuse to take pictures of random people."

Masquerade clad stilt walkers roamed the sidewalks taking pictures with families and visitors. Walking slowly, they were able to avoid children excitedly escaping from parents and small dogs. They had a table setup where children could make their own masks...now if only they setup a station for adults!

To live up to the street party theme, a block was closed off for traditional Italian dance lessons. This was the reason I brought the Canon S90 point and shoot instead of my 5D. The S90 has image stabilization, whereas I own no SLR lenses with IS built in. Still, my shutter speed was close to 1/4-1/10th of a second, which meant waiting for the dancing to stop in order to take a picture. Yes, the middle picture is an intentional artistic rendering to show motion of the dancers.

What's a party without music? In comes the Teagan Taylor Trio. There were four of them...? Maybe the band is heavily influenced by the Survivor reality show. At the end of the gig someone gets voted out of the group. "Sorry John, you missed a note on Bye-Bye Blackbird. The group has spoken." Then again, maybe it's a situation like Spinal Tap where they keep having their drummer spontaneously combust. Dunno. The group was perched on the southern most street corner of Little Italy belting out classic lounge jazz and blues tunes all night.

That's it. I need sleep after all this partying.

Tuesday, March 1, 2011

••◊ Vectorscope. Friend or Foe?

While I'm waiting for projects to get kicked off this month my mind is wandering into the deep forest of technical knowledge. I sought enlightenment from my desk chair man cave and began to meditate on the concept of camera color calibration. No camera, no matter film or digital, cheap or expensive, seems to be calibrated for proper color reproduction out of the box. Why can't we simplify our existence with the comfort of proper hue and saturation? Why? What if my camera could, through a insignificant amount of pain and suffering, be calibrated? Wouldn't that make the world a better place?

So I whipped out my web browser and went to the keeper of all knowledge - wikipedia. With video the common tool to examine hue, saturation, and color reproduction in general is the vectorscope. As with most seekers of enlightenment, expensive toys are out of the question. A solution? Microsoft Excel. Yes I know that Premier Pro has a vectorscope, but it only handles NTSC so it doesn't work for the modern world of HD video. Adobe After Effects has one too via Synthetic Aperture, however that scope has issues too and I still haven't found out what it really plots. A proper vectorscope works with the Y'CbCr color space, which turns out to be a simple transformation from the RGB colors in video. All I had to do was look up the correct matrix multiply and viola! ...Excel vectorscope. Now I can look at hue and saturation in the rec.709 color space (HD) without the cost of buying a brand name test and measurement device.

The picture above shows my less than glamorous vectorscope plot of a few RGB values. The empty boxes represent the standard 75% saturated color values that everyone in the industry uses for color calibration. The asterisks represent the color reproduction of a Canon 5D mark II in video mode, with the faithful color profile and saturation turned down one notch. Note that the calibration target was a Red Cambook made by DSC Labs. Ben Cain over at negativespaces.com did this measurement a while back since he owns the Red Cambook and a 5D mark II.

Now the question becomes, what do I do with this knowledge. Well... I search for the ideal of course. The solid squares in the above plot represent the idea color reproduction for HD video. Canon provides a little used piece of software with their cameras called the Picture Style Editor that actually allows you to tweak the color reproduction of the camera. So using the asterisks as the source colors and the squares as a target color I began to twist the color reproduction into shape. Blue was the color most in need of tweaking. Magenta needed a little more saturation, but other colors needed only very minor shifts.

What you see in the above pictures is first, the picture style editor with color tweaks at each of the calibration targets. Next is the final pictures. Notice that if you look closely, the color of the car has changed. The woman, the ground, her clothes...etc are all pretty much the same. There is a little more saturation with the red stripes in her shirt because they probably have a slightly magenta tint, but skin tones are pretty much unchanged.

Am I done? No. I don't have a way to verify this custom picture style without a Red Cambook. It's even difficult to rent one of these. What I can say is that after viewing many, many photos with varying content the only significant shift is in blue. I don't have a picture with much magenta in it so I can't verify that test condition. So my journey is not done. I still need to innovate a test case and prove my work. My eventual goal is to create a custom profile and release it to the world, but until then I am in search of a Red Cambook or other DSC Chroma DuMonde target.