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Thursday, August 25, 2011

••◊ GoPro - It Certainly Does Go.

Clarence bought a GoPro camera last weekend and let me borrow it for the week to figure out the work flow to integrate the footage into our normal HDSLR productions.  The first thing I had to do it pick this little action camera apart and figure out how it really works.

The first items I checked for are exposure lock and white balance.  No check on either.  Everything is auto, i.e. designed for common consumers as opposed to advanced consumers or professionals  What this means is that the camera is no-go for time lapse or high contrast night scenes.  Notice how all the GoPro example videos on their site are outdoors during the daytime?

Also the lens on the GoPro HD has a fixed focal length - EXTREME wide - and doesn't seem to include a mechanical aperture.  There's a reason that the footage is very jerky and artificial.  They are just adjusting shutter speed in order to control exposure and in daylight that shutter speed is just a small fraction of the frame rate - thus jerky motion.  What I haven't explored is frame rate conversion to 23.976fps (24p) for film making.  It might require some motion blur added in post to control the motion and not make it so jerky.  This is good and bad.  A fast shutter speed makes it easier to frame rate convert for artificial slow motion using Twixtor/Optical Flow/Pixel Motion .

The next area I wanted to look at is the color rendition.  There are two 1080p HD modes on the camera, PAL at 25fps (25p), and NTSC at 29.97fps (30p). Normally a prosumer camera would translate the internal camera capture color for the color differences between PAL (Europe) and NTSC (North America) displays, however from the two photos below you can see that there is no color difference between the PAL and NTSC mode.  Essentially the GoPro camera is ignoring color rendering difference between a PAL and NTSC (also rec.709 HD) display.  What is really surprising is that they don't offer a rec.709 (modern HDTV) or sRGB mode (PC) options.The top picture is from PAL mode and the lower picture is from NTSC mode.  What this means to the post work flow is basically *good luck* trying to get the footage to match to other cameras.  It's going to take tweaking and lots of it.

With just a glance at the gray tiles on the test chart you can see that this camera only has about 5-6 stops (my estimate) of exposure latitude.  Can't take this thing into a contrast-y scene without serious highlight blow out or shadow crushing.  Not necessarily a deal killer, just something to be aware of.

Now for a more scientific view of the color rendition I turn to my handy dandy Excel based vectorscope.  The first chart compared sRGB (PC display) with the GoPro output.  The circles are the desired color targets and the diamonds are the actual measured colors.  Skin tones look pretty good, however the primaries are way off.  Red, yellow, and green are all over saturated and miss their hue mark.  Magenta has the right hue, but is slightly under satured.  Blue is WAY off on hue and compressed toward cyan.  Cyan is WAY, WAY over saturated.  This tells me that the camera is going to have clipped color channels because of the over saturated color rendition they chose to implement.  Since the color seems to be so uncontrolled, it leaves me wondering what will happen when we try to use two of these cameras at the same time.  Will they render color in the same way?  Dunno, but will find out soon.  

Rec.709 (HDTV display) color rendering has about the same issues in the same places.

So what's really excellent about this glorified web-cam?  The accessories.  You can mount this camera to just about anywhere and it's indestructible.  A team used the camera on the 48 hour film project recently and the camera fell off the car mount while the car was moving along at speed.  The camera still worked after getting flung onto the asphalt.  Try that with your $4,000 HDSLR!  You can get the aforementioned car mount, surf board mount, bicycle mount, helmet mount, or just use a set of zip ties and duct tape.  You can even get an LCD display that mounts on the back to frame your shots and review footage in the field.  ...and for the really adventurous cross-eyed sort there's the 3-D configuration!  The accessory people at GoPro really know how to capture the market.

We're planning on strapping a couple of these cameras to fast Porsches and letting the cars rip along in a chase scene in the next few weeks.  Should be fun ...and if the cameras fall off, no big deal.

Thursday, August 18, 2011

••◊ 48 Hours - It's a Wrap

Last night was the screening of our 48 hour film "Box."  They had a red carpet, photographers, videographers; essentially an excuse to play dress up.  I mean, I knew I was going to be standing next to three incredibly beautiful women most of the night (many thanks to Clarence) and I didn't want to feel wholly inadequate in their presence - so I played dress up too.

It's a nervous rush to the pleasure center of the brain any time your film is shown in front of an audience on the big screen.  I guess that's what brings back directors for more self-abuse, ...the big screen crack addiction.  On top of that people were voting for audience choice awards with those third size pencils and green ballots of fate.  However, it's not all nerves.  Some of the projects presented are excellent work for 48 hours and it's good to just support the relatively small San Diego film maker community - compared to our northern neighbors. 

Below are some of the random documentary photos I took during the evening.

Our actress Stacey and graphic artist (and location scout too!) Karen.

Fred and his daughter Victoria, both actors in our film.

Our cast and core crew on the red carpet...left to right: Karen, Fred, Mark, De'Anna, Frank, Victoria, Stacey, Gregg, and Vincent.

Our supermodel friend Shealyn, some weirdo, lovely Lydia, and femme fatale from Vermont Kristen.

Ben showing off one of our box props.  Ben was a lead writer on the film.

That's Frank, our director, in the middle of the audience holding up the box, although I have to admit that with the large depth of field this is more of a "Where's Waldo" photo.

Kristen and Lydia giving a pre-show self paparzzi Facebook update.

After the screenings Duane Trammell, the 48 hour organizer for San Diego, does a couple minutes of interviews with the directors.  We're #7 in the background.  It's interesting that the frame they chose was the "chicks with knives and guns shot", don't you think?  Maybe that's what excited the 48 hour program editor....hmmmm.

The voting ballot.  Darn tootin' they voted for "Box."  The alternative was a long walk home in high heels...he,he.

Every premiere has a wrap party.  So this is where I leave this adventure, with a lime slice on top.

Monday, August 15, 2011

••◊ Getting ACTUAL 5500k Out of Promaster Fluorescents

Just an immediate heads up that this is a tech-worthy nerd blog entry for those inclined.  From my last blog entry you probably know that last weekend was my first foray into 48 hour film making.  Fun but challenging.  Also challenging was the budget.  We needed daylight balanced lights, but didn't have the budget to rent Kino's or a set of Arri HMI Frenels.  A couple sets of the Lowel Tota's magically (i.e. tragically) showed up, but I personally never want to deal with the issues they've created for me again.  However we did have our made-somewhere-in-Asia cheap Promaster 3-in-1 fluorescent lights.  Promaster also sells the bulbs rated at 5500k (daylight color temperature), which should have made life easy, kinda-sorta.

Like most cheap Asian products the advertising doesn't quite live up to the promise.  What, you say?  Low cost companies provide misleading specs?  Nah, never happens (sarcasm implied).  The bulbs are nowhere near an accurate 5500k color temperature or any daylight sort of balance.  As DP I knew I needed to move fast on this shoot and not be solving ridiculous color balance issues, so I came up with a reasonable solution - thus the subject of a new tech blog entry.

First, I think I need to show my test setup. I put a Gretag White Balance card in front of my camera lit by the Promaster bulbs with the camera white balance set to 5500k.  The test card should be a completely neutral color when the bulb color temperature matches the camera settings for white balance.  For those curious nerds ...no, the tungsten bulb in the background made no difference.  I turned it on and off to check.

Click on the picture below to see the RGB spectrum of the bulb.  Red is approximately the same as green, but there isn't enough blue.  If the green was mid-way between red and blue then it would just be a matter of adjusting the camera white balance color temperature to match - no luck there. 

The answer to this issue comes in the form of a Rosco #3208 quarter-blue gel.  I actually pre-tested this using the free color swatch book they give away at the dealers.  At first I was at another dealer who sells Lee brand gels and bought quarter-blue with the dealing telling me they were equivalent.  They aren't.  If you hold both up to the light you'll see that the Rosco is more purple-blue and the Lee is more cyan-blue.  So test before you buy.  All I can recommend at the moment is the Rosco gel because I don't know if Lee or GamColor make color spectrum equivalent gels.  They might, dunno.

This was my test setup.  I simply put the gel in front of the lens to ensure complete coverage.  As I mentioned before this was initially done with just the free swatch book sample.  Low cost!  The gels tend to hover around $7/sheet, so they aren't significantly expensive either.

The RGB "fixed" spectrum is shown below.  Notice how the red equals the green equals the blue?  Now that's good white balance!  The added benefit is that if I'm using this light as a key light I can just set the white balance to 5500k on the camera, gel the lights with the Rosco quarter blue, and not have to worry about white balance - i.e. I move like a grasshopper strapped to a bottle rocket from location to location.  Also the lights now better match daylight, making my life of dealing with mixed lighting problems a tiny bit easier.  No more yellow-green lighting to deal with.  Yeah! ...might also mean more time for the craft services table.  The downside? ...well, like with any gel you lose a bit of light.

The real news is that the solution does work and it's battle tested in the field as of last weekend.  It's also an order of magnitude cheaper than the Kino or Arri solution, for lower lighting power needs at least.  Enjoy!

Wednesday, August 10, 2011

••◊ It's a 48 Hour Mad, Mad, Mad World

This last weekend was the madness that represents the 48 hour film project contest in San Diego.  You get a genre, line of dialog, character name, and prop at 7pm on Friday and have to turn in a fully finished film by 7:30pm on Sunday.  The clock picture shows how close we were cutting it and this isn't even the time the director left with the film!  Last year there was talk of the delivery vehicle hitting 115mph down I-163 at 7pm while the computer was still rendering out the video!  Talk about extreme editing.  Now there's an idea to pitch to Jerry Bruckheimer for a new reality show.

My friend David, also an actor in our film, was down from LA and suggested that we visit the NAS production studio out of curiosity on Sunday just as they were wrapping up work.  Let me tell you, immediately upon entering the place smelled like a World of Warcraft LAN party.  People hadn't showered in two days and soda pop was spread around every table.  You can see 1/3rd of our CG render farm in the far right of the picture.  The final edit was still going on in the office just adjacent to this picture.  We even had to re-record some foley in the kitchenette around the corner just 20 minutes before they left.

I managed to capture the final hand off.  The flash drive Sony provided to the 48 hour teams was too slow to copy the video on time and deliver it, so they copied it onto a portable hard drive, then copied from the portable hard drive to the flash drive while in transit to the film drop off event.  Yes, we cut it this close.  The director was somewhat delirious from the last two days of hard work in production (can't blame him one bit), so he had to be driven to the event.

Another team I know had their drop off person running from the car to the drop off point in the last two minutes before the deadline and managed to bang up her shin on the concrete during a brief fall.  She'll heal, but more importantly the film arrived on time!  Ahhhhh, the glory.  Only 48 of the 66 teams turned their film in on time according to the event organizer.

Here's a brief screen capture of the last scene I filmed on Saturday just before midnight.  The lighting is four bare bulbs just behind the furnace in the middle of the picture, a soft box coming down the corridor on the right and a small front fill from the camera position.  The lighting was inspired by Star Wars, with its depiction of characters in industrial settings.  That's all I can give you.  To see more you have to come to premiere night August 17th and see it on the big screen.  *I* don't even know what the film looks like, but when you see the sausage being made you don't necessarily want to eat it right away.  I acted as DP for a large part of the filming and while in a rush the director took Clarence and used him as a second unit DP for scenes I haven't seen yet.

Speaking of Clarence, he made a behind-the-scenes picture montage video from our two days of production.  Yeah, that's me chowing down a sandwich in the background.  Enjoy!

UPDATE: Just added overnight - a trailer for the film.  I was wonder how long a trailer for a 5.5 minute film would be.  Answer - 15 seconds.