Archive for the ‘HDV’ Category

DEAR GOD, MAN! Auto-Exposure From Hell !!

Friday, May 1st, 2009

So I’m eagerly awaiting the delivery of these “ultra important” HDV tapes that are supposed to becoming for transfer. And right on time, the FedEx guy shows up with a box. I open the tapes, pop one in the deck and… it’s an interview with a high profile celebrity. The sound is perfect. The color is rich… but wait… what the…. OH NO! They shot the celebrity with the auto-exposure turned on. Say it ain’t so!

The tape looks wonderful, but every time the guy leans toward the camera or leans back (which seems to be about every five seconds because the guy is pretty animated) the exposure changes. He’s wearing a light shirt and the background is pretty dark. So when he leans forward, the entire image darkens by about 1/4 stop. Now, that may not seem like much, but 1/4 stop in HDV is like someone fired up an extra 2K softlight in the room. Then the guy leans back and everything goes back to “normal.”

The thing is, there is no way they are ever going to re-shoot this footage, so the only thing to do is fix it. Enter Kirk. A lot of you may have all kinds of ideas about how to solve this problem, but here’s the way I did it:

First I marked each transition where the picture density changed. It turned out to be 83 times across 4 tapes. (Most of the footage was of the brighter variety.) Then I measured the length of each transition. They ranged from about 2-14 frames.

Then I duplicated the sequence.

In sequence number one, I dissolved to black (actually it was emptiness) at each “bright” transition, then dissolved back up at the next transition. So I was left with a whole sequence of nothing but the “normal” footage in the timeline that kept dipping to nothingness (alpha channel).

In sequence two, I did the exact opposite, ending up with all the bright footage, dipping down to nothing at the transitions

Then, I took the “normal only” sequence and played with the density until it matched the look of the bright one.

Next, in After Effects, I composited the two sequences on top of each other, making it look like one long sequence of “bright” footage. I flattened it by nesting it in a new composition. Then I played with the density and contrast until the “bright” footage looked as normal as I could get it.

Then I laid it all back to HDV tapes to have a clean archive master of the adjusted dailies.

How did it look? By my eye, I could see the changes at each transistion. But that could have been because I was looking for and anticipating each change. The client was more than pleased with the adjusted footage. And in the end, when it was all cut together in an EPK, it was downconverted to digibeta and looked amazing. Nobody would ever be able to tell. The biggest shock about the adjusted footage was the producer’s face when I handed him the bill. But it was certainly cheaper than the alternative of not having the footage.

Today’s lesson: NEVER EVER shoot with auto-exposure on unless you are doing run and gun paparazzi work … or home videos.

HDV to Standard Defintion – Go for the letterbox!

Thursday, September 13th, 2007

HDV is the little brother to broadcast High Def such as HDCAM or D5. It shoots/records in the 16×9 aspect ratio which, for the math inclined is the same as 1.78 : 1 But standard def television uses an aspect ratio of 1.33 :1

So in down-converting the HDV to standard, you basically need to force the shape of a longer rectangle into a the shape of a regular TV which has a more square shape. (see examples below)

The two ways of doing this are to hack off the sides of the rectangle (also called a “center extaction”), which still provides excellent resolution . But in that case, the sides of the picture will be gone. For example, if there is a dinner table scene and one of the actors is far to either side of the frame, they will be cut off.

However, if you want to see ALL the image, then the long rectangle needs to be shrunk down to fit inside the square. This means there is no image at the tops and bottoms of the frame in the standard def tv. It’s letterboxed. The black bars at the top and bottom are just “empty”areas where there is no picture because it has been shrunken down.

Letterbox is widely accepted on broadcast tv these days. Many network shows run this way due to the complications of trying to have different versions for high def and standard def. People are used to it and the filmmaker’s compositions are preserved. So shoot/record/ dub your HDV into letterbox when you put it on a regular tv. It looks cooler, and the dude at the dinner table isn’t cut off.