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My Love Affair with Alexa

When the camera sees more than my light meter does, it's time to acknowledge that the game has truly changed.

By Art Adams | August 20, 2010

Left to right: Me, camera assistant Paul Marbury, gaffer/DCS chapter president Simon Sommerfeld, and Leigh Blicher, co-owner of Videofax.

My intrepid crew of volunteers included DCS chapter president Simon Sommerfeld as gaffer; camera assistant Paul Marbury; Adam Wilt as behind-the-scenes documentarian; and Jim Feeley as production assistant. Also accompanying us was Michael Bravin of ARRI and Leigh Blicher, co-owner of Videofax, who provided us with nearly all of our support gear. (Chater Camera supplied two lenses, but the rest of the gear came from Videofax.) Our talent was Colin Stuart, who appeared in both my WEAVE and Facebook projects.

Our goal: to shoot a mysterious man walking through San Francisco, surrounded by shapes that are, at first, completely unnoticeable; eventually the edges of the shapes start to glow and we realize that our character is constantly surrounded by them. The shapes will take on meaning after the visual effects are completed, and I won't ruin that surprise until that project is competed. Ian and I scouted three locations, two of which we used: The Embarcadero, a street and promenade that winds its way along the east side of San Francisco, along the piers; and Treasure Island, a man-made island built by the military halfway between San Francisco and Oakland. Our third location, on Telegraph Hill, offered a spectacular view of the Transamerica Building. Unfortunately the fog was so heavy that night that the building was completely obscured, so we wrapped after shooting at Treasure Island.

Oh, and we shot entirely without permits. Which wasn't hard as we basically looked like a news crew with a few more people and a couple of additional cases.

The entire piece was recorded to SxS cards in ProRes4444 and LogC. LogC is a Cineon-based log curve that captures everything the sensor has to offer and makes it available for grading. Log curves are not raw, but are actually more efficient than raw as storing raw linear data wastes quite a lot of space. Log gamma encoding captures more than enough information to stand up to very aggressive grading. (I hope to write an article in the near future specifically about ARRI's LogC implementation.)

The camera was rated at EI 800, and the shutter varied between 180 and 270 degrees. The white balance was set to 3200k and never budged. The frame rate was 23.98p. I'm going to talk about the shots in the order that they appear in the montage, not in shooting order.

The first shot in the piece occurred well after dark, and not long before our move to Treasure Island around 10:30pm:

Close-up of the Bay Bridge from The Embarcadero near Harrison St. This was a grab shot on a 200mm Nikkor lens, shot wide open at T2. This is the graded version.

This is the same shot in LogC, ProRes4444, ungraded.

Just before our location move we grabbed a number of shots, including one where we shot through the window of a local restaurant. We just wanted to see what we could get. I didn't bother with a meter reading as there was no point. At one point earlier in the evening the fog read T0.5 reflected. This was shot with a 270 degree shutter.

Talent Colin Stuart in front of the Bay Bridge. 85mm Super Speed, T1.3, 180 degree shutter. Bright side of face read T1.4 incident. Fill is from ambient street lighting. This is the graded version.

This is the same shot in LogC, ProRes4444, ungraded.

This was the first shot that we lit all evening:

That's gaffer Simon Sommerfeld holding a LightPanel Micro. Most of the light in the shot came from the left side of frame, so I asked Simon to pop up the frame left side of Colin's face for a little more contrast. I've found great success in following the direction of the ambient light and enhancing it, rather than fighting it, and using the Micro from the left of frame hid the fact that it was a separate and additional source. It increased the contrast on Colin's face by popping the existing highlights as the ambient streetlight tended to be a little flat.

Left to right: Leigh Blicher and Michael Bravin observe while I look through the viewfinder, Paul Marbury pulls focus between Colin Stuart and the bridge, production assistant Jim Feeley conveys instructions to Colin via radio, Simon Sommerfeld holds the LightPanel Micro, Colin stands on a lens case for height, and Ian McCamey directs from near the camera position.

Around this time I took a few meter readings and discovered that the bright sky under the bridge, lit by the Port of Oakland in the far distance, read T0.7 5/10 and the fog over the bridge read T0.5 1/2. I was a bit baffled because everything looked brighter through the viewfinder, and on the on-camera monitor, than my meter said it should, but at some point I realized that the Alexa was showing me things my meter couldn't even read.

This is a situation were a large HD monitor would have been very helpful. I couldn't judge the quality and direction of the fill by eye as it was incredibly dim, and the small on-board monitor didn't allow me to see a lot of detail. At T1.3 and EI 800 a good-sized monitor is necessary to see what kind of image you're really capturing as the monitor will be brighter and crisper than what the eye can see on its own.

On a real production I would have flagged a certain amount of the fill off of the right side of Colin's face for a more dramatic feel. My sense is that night/exterior cinematography with this camera will be more about the grips than the electricians: the crucial aspect of lighting will be removing the sources that you don't want, and slightly enhancing the ones that you do. That's not to say that an electrical crew won't be necessary-far from it!-but we'll be doing more with fewer lights and spending additional time removing sources rather than adding them.

Handheld with an 85mm lens at T1.3, 270 degree shutter, pulling my own focus.

This is the same shot in LogC, ProRes4444, ungraded.

I'm going to group this shot with a couple of others that we shot around the same time:

Handheld, 85mm lens at T1.3, 270 degree shutter, pulling my own focus.

This is the same shot in LogC, ProRes4444, ungraded.

Same shot as above, but walking with Colin toward the bridge.

Same shot as above, ungraded LogC.

This shot generated some concern on the Cinematography Mailing List as a number of people assumed that they were seeing "jello-cam": as the camera moves abruptly the out-of-focus lights in the background appear to smear and change shape, as one might expect with a rolling shutter. I stepped through these frames one by one and determined that the effect seen is not that of rolling shutter, but a combination of using a 270 degree shutter and cat's eye vignetting:

Figure 1: In the frame above we can see some motion blur from the 270 degree shutter, and a number of the lights are ovals instead of circles. The ovals are due to cat's eye vignetting, where out-of-focus highlights near the edge of the frame are cut off by the aperture opening. Click here to read the best explanation I could find for this phenomenon. Keep an eye on the highlight toward the left of frame, next to Colin's ear, as we're going to watch what happens to it over the course of the shot.

Figure 2: The above frame is relatively still and occurs during an abrupt change in camera direction. The motion blur from the 270 degree shutter is gone, and the bright highlight that was vignetted before is no longer cut off as it is now near the center of the frame, where the effect disappears.

Figure 3: This time the bright highlight near Colin's ear is shaped differently to the first one. It has resumed its cat's eye shape by drifting left, away from the center of the lens, and the shape is oriented differently from the first image above because the highlight falls above the horizontal mid-point of the lens. In figure 1, above, the cat's eye shape is different because it falls below the mid-point of the lens.

A line drawn through the short axis of these cat's eyes passes through the center of the image. The cat's eye vignette increases in strength the farther it gets from the center of the frame, and the short axis is always oriented toward the middle of the frame.

The arrows bisecting the cat's eye don't line up perfectly with the lens center but you can clearly see what's going on. The combination of motion blur and the changing shape of the bokeh can give the impression of jello-cam but I see no evidence of rolling shutter artifacts whatsoever. The cat's eye vignette is lens-dependent, and these old Zeiss Super Speed lenses appear to be the culprit. The vignette is easily removed by stopping down a few stops... which is not going to happen when shooting entirely by the light of existing street lamps. (The light on Colin read T1.4 incident when he was directly in front of one of the streetlights.)

If you're curious as to why the shot was so bouncy, that's because I was operating it like this:

Left to right: Director Ian McCamey, camera assistant Paul Marbury, me, gaffer Simon Sommerfeld.

Let's take a quick trip over to Treasure Island:

Colin in front of the Bay Bridge, on the edge of Treasure Island. Lens is the 200mm Nikkor T2, at T2. The "key" on Colin's face is T2 incident.

The same shot, ungraded, in LogC.

This was shot around 11:15pm on Treasure Island. We'd shot some scenics farther up the road as I was paranoid about moving near the guard shack that controls access to the rest of the island, but the light was better here and we needed to shoot past the end of a wall that threatened to obstruct our wide shot. We worked quickly and quietly so as not to wake the guard.

Here's the wide version:

Wider shot, same location. Lens is an 85mm Super Speed at T1.3. 180 degree shutter. The "key" on Colin's face is T1.4 incident.

The same in LogC.

The bright light in the lower right of frame is the stadium lighting in AT&T Park. Apparently there was a game that night.

Here's the extent of our lighting:

Simon Sommerfeld lights with the trusty LightPanel Micro.

Once again we're following the direction of the ambient lighting, which is coming from a parking lot on camera left. The LightPanel Micro is making the bright side of Colin's face a bit brighter to "pop" it a bit. If you're curious about the fill level...

Me, reading the ambient fill level.

A blowup of the above, showing what my meter reads.

Yikes. Colin's face almost looks flat-lit in the LogC version of the wider shot. It's a little crisper on the close-up as that lens only opens up to T2 instead of T1.3, so the fill is a stop darker than it was on the wide shot. It's amazing what one small light can do, especially if you're using it to augment the lighting that's already there. (We moved the Micro in on the close-up to build the "key" level from T1.4 to T2 incident.)

Once again, notice the cat's eye vignetting on the highlights in the background near the left and right edges of frame.

More low-light goodness can be found on the next page...

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Dennis Kane: | August, 20, 2010

Thank you Art for taking the time to explain the details of each scene. This montage was even more impressive when projected on the big screen at the DCS meeting. Very impressive

Art Adams: | August, 21, 2010

Thanks, Dennis! It was very good to meet you at the DCS meeting. I’m glad you enjoyed the article. As I watched the montage projected I thought to myself, “Enjoy this, it’ll never look this nice again…” smile

cineshashank: | August, 21, 2010

Hey Art
A real nice write up on ARRI’s new offering to us ALEXA. I am just a bit confused here about a fact may be I have no knowledge about. When you are referring to grading here is it digital grading done on computer software or optical grading done in lab. Please throw some light.

Scott Simmons: | August, 21, 2010

Great piece Art. Let’s hope that Arri’s inclusion of ProRes in the camera means they know something that we don’t about Apple’s longterm commitment to ProRes and the Pro Apps in general.

Art Adams: | August, 21, 2010

Hi Cineshashank- it was digitally graded via Scratch, a DI tool from Assimilate. Lucas Wilson of Assimilate brought a Scratch system with him on a PC and we sat in a corner and graded the footage during Michael Bravin’s Alexa presentation.

Scott- Amen to that. Apple has done this industry a world of good, but our industry also hates unpredictability.

evandroc: | August, 21, 2010

great article!
thanks Art! maybe by now I don’t have enough money to get it… but now I know exactly where I wanna go…
Evandro Cruz/DP/Brazil

watcher_skys: | August, 24, 2010

very impressive but I want to see what it looks like on a TV or projected because the clip, as posted, looks much more like video to me.

IEBA: | August, 24, 2010

All I get is a “Waiting for Video” in a black box.
is the video clip posted?

Art Adams: | August, 24, 2010

It is, and it works for me. I’ve noticed that Chrome has trouble with Quicktime movies-it doesn’t buffer them but waits for the entire thing to download-so it might be worth trying other browsers if that’s the one you’re using.

Allan: | August, 25, 2010

A local rental company has them in and available for rent. Problem, $5K per day. I think that was for a package, at least I hope so but that ended the conversation. I can get a RED Package easily for $1500. $2000 if I want to splurge on on Master Primes (4 - 5 Lenses). Regardless of marketing bullshit from both RED and Arri and various tech benefits to one or the other, that is a $3K price difference. $9K on a 3 day week. Might not matter on a $50M+ budget but on $100,000 commercial day, 3% of the total budget just for the ‘privilege’ of using and Alexia doesn’t make any sense to me. As a producer/pm Alexia has to cost the same, a competent DP is going to make either one shine. Hell I can shoot 35mm for less than price difference.

Art Adams: | August, 25, 2010

Sorry, I’m calling “bull” on that. There’s no way an Alexa costs $5k per day. That’s as much, and slightly more, than a Phantom HD Gold would cost, and there are a lot more Alexas around than there are HD Gold’s. An HD Gold is a quarter million dollar package; an Alexa is $70k.

Alexas will rent for about the same price as an F900 did when it first came out because they cost about the same new. The Alexa will be more than a RED on a daily basis, because it costs more to buy, but there’ll be a significant savings in post due to the lack of need to transcode.

If you’re going to make up stuff like that here you’ll have to be a lot more convincing. You’ve either not done your homework or you’re just outright lying-and not very well.

Misha Mazor: | August, 25, 2012

Why did you change the shutter speed on some of the shots?

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