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Saturday, March 15, 2014

••◊ Desert Yoga with Danielle Orner and Aerial Mob

I wanted to drop a few picture on ye ol' cinematography blog of our current production in progress.  Tommy and I had a chance to team up with Aerial Mob and Danielle Orner for a inspirational short film in the Anza-Borrego desert last weekend.  You can see our caravan parked at Stag Cove just off of Highway 78 in the photo above.

I was the director of photography and camera operator, so I could only whip out a point and shoot while we were stopped.  The first picture below shows the Panasonic GH-4 prototype camera that was on loan to us for the weekend.  We were shooting in 4k and even did some over cranking in HD at 96fps for one shot.  Jon, pictured in the white shirt, is one of the engineers at Aerial Mob and he acted as on-set engineer for the new handheld stabilizer they are developing.  A funny thing that you might notice in the picture is that we had to improvise a sun hood for the monitor with painter's tape and a Trader Joe's spanakopita cardboard box.  Thank goodness I was hungry for Greek food the week before the shoot.

Peter from Bad Cat Films, shown in the second photo below, was my AC and all around grip/gaffer/go-to guy to get things done.  We ended up not being able to use the 6x6 bounce frame in the shot and had to rely on a handheld silver bounce instead.  It was too windy with the Santa Ana's blowing through.  That, and I didn't want to explain to Video Gear why their Ultra-bounce had cactus needles piercing it everywhere.  However, we did end up using the shovel I brought to dig holes for c-stands when one of the guys got their van stuck in the sand.  Strangely, the Toyota Matrix made it through fine! 


Aerial Mob currently mostly does aerial shots using their octo-copter.  One thing I didn't realize is how short the flights have to be because the batteries get drained very, very fast.  On the copter we had a Red Epic camera from Blair Paulsen at Alacrity Media Epic with a 18-55mm zoom plus variable-ND and power coming from the copter rig to keep things light enough.  The lens was about the same weight as a 24mm Canon L-series prime, so given the choice we went with the zoom for quick change flexibility.  We took a chance with mixing the GH-4 with the Epic, so I'm hoping things work out in the color grade (fingers crossed!). 

Unfortunately it was too windy to fly until nearly 5pm due to the Santa Ana winds.  After that the Aerial Mob boys fired up the copter and buzzed Danielle a few times with epic model shots (no pun intended). 

Today Danielle recorded the voice over for the piece, so that part is at least done.  Next we need some music, editing, and color grading.  Hopefully we'll have something to show by the end of the month.  Lots of work to do.

Wednesday, March 12, 2014

••◊ Calculating Depth of Field

I was on a shoot this last weekend and we were having massive focus problems due to equipment issues.  Another cinematographer on the shoot suggested that I just give up and close down the aperture to get more depth of field.  Well..."how much?"  So today I'm setting out in an endeavour to further understand depth of field/focus depth.

The first factor that you need to take into account is the circle of confusion (CoC).  This factor is determined using a number of assumptions related to viewing conditions and determines the amount of "acceptable" blur given a sensor size.  For instance, most cameras I deal with now days have a sensor size approximately the same as APS-C photography sensors.  So given the generally accepted d/1500 standard, that gives us a circle of confusion of 0.018mm.  HOWEVER...and this is a big however...there are different suggested rules of thumb for CoC and even different CoC's suggested by brand of lens.  For instance, Zeiss suggests 0.025mm CoC for their Master Prime lenses.  Some people estimate 0.02mm and some estimate as much as 0.05mm for 35mm movie film.  That's a great deal different!  So I'm just going to show example calculations using the d/1500 standard so I don't start an argument on who's right!  Perhaps the ASC has something to say on this(?)

Given the CoC figure, there are a few formulas to calculate the depth of field.  We first calculate the hyperfocal distance.

H = f^2/(N * CoC) + f

H is the hyperfocal distance
f is the focal length of the lens (i.e. 50mm...etc)
N is the lens number (i.e. f/1.4 or f/11...etc)
CoC is the circle of confusion

So let's say we are photographing a person with a 50mm lens set to f/4.0.  That gives us H = 2500/(4*0.018) + 50 = 34772 millimeters or approximately 34.8 meters.

Next we'll calculate the near (Dn) and far (Df) distances that are sufficiently in focus given our chosen circle of confusion (CoC).  The quick formulas assume practical values of H are larger than the subject distance.

Dn ≈ (H * s)/(H + (s-f))

With the actual formula being...

Dn = (s*f*f)/(f*f + N*c*(s - f))...if you need to be more exact for whatever reason.

H is the hyperfocal distance
f is the focal length of the lens
N is the lens number
s is the distance from the camera to the subject being photographed.

Again, let's choose an arbitrary distance of 3 meters (3,000 mm) for the subject distance.  This gives us Dn ≈ (34772*3000)/(34772+3000) ≈ 2765 millimeters or about 2.77 meters.

Df  ≈ (H * s)/(H - (s-f)) given that s < H

With the actual formula being...

Df = (s*f*f)/(f*f - N*c*(s - f))...if you want to geek out.

At 3 meter subject distance that means Df ≈ (34772*3000)/(34772-3000) ≈ 3278 millimeters or 3.28m.  In all that gives us a depth of field of about 0.52 meter.

There are some other interesting findings from this formula.  Let's say the person is standing exactly at the hyperfocal distance - 34.7m in this example.  Then the Dn ≈ H/2 ≈ 17.4 meters and Df =∞.  Also if the person stands beyond the hyperfocal distance then Df will continue to be infinity, however closer objects are still subject to the focus limits of Dn.

I applied these formulas to the Arri Master Prime depth of field chart and found a great deal of discrepancy at 14mm and at 50mm.  But then I remember that these are T-numbers that take into account the efficiency of the lens as well as aperture.  So at T/4 the 50mm lens has an approximate f-number of f/3.3.  Makes sense.  Something else must be going on with wider lenses because I couldn't get the formulas close to their chart numbers. 

Total geek out over.

Saturday, March 8, 2014

••◊ Review of the Panasonic GH4, first look.

This weekend I am the director of photography for a shoot planned in the Anza-Borrego desert with director Tom Friedman, Aerial Mob, and model/yogini Danielle Orner.  The guys at Aerial Mob were able to steal a pre-release Panasonic GH4 camera for the weekend.  Unfortunately it has to go back on Monday, but for now it's mine...ALL MINE ("buhhh, ha, ha, buhhh, ha, ha" implied) to use for this weekend's cinematography.  Video Gear also provided an Ultra-Bounce 6x6, stands, shiny reflector, and backup camera, so I have to give them a shout out.  I'll be providing more information on their blog in the next week or so. 
The plan is to use this this camera on a new handheld stabilizer that hasn't been released yet, but needs demo material.  A prototype camera AND prototype stabilizer...what could possibly go wrong?  I did have a chance to try out the stabilizer today, and while it's not quite ready for a photo session, it's working.  Likewise, there are features on this GH4 camera that are not enabled yet, but it's working.  Most importantly the 4k recording feature, which we plan to fully utilize this weekend along with a Red Epic on Aerial Mob's octo-copter.
Since the shoot isn't until tomorrow all I can show are some basic product features and talk about what I've learned so far.  First, the demo camera arrived without media and we were first told that the camera would only record 4k with UHS class 3 cards.  That turned out to not be correct.  You can use UHS class 1 cards with write speeds of 45MB/s or higher.  The 40MB/s and slower cards can't keep up.  When we talked with the local Delkin rep he recommended the ELITE 633 cards.  We found other brands work equally as well.
There are two "flavors" of 4k resolution recording available, C4K (true 4k) and 4K (Ultra-HD).  There are also three flavors of HD (200Mb/s All-I, 100MB/s, and 50Mb/s).  In HD you can shoot up to 96fps! 

The base ISO on this camera is 200.  You can select up to 6400 ISO.  I don't want to comment on noise at each ISO setting because this is a prototype camera.  We'll be using it at ISO 200 tomorrow, so I won't have a chance to thoroughly evaluate it anyway.

Here's a look at the left side of the camera.  Note the mic AND headphone jack!  Finally!  Also on Panasonic's website they say that the camera has a mini HDMI, but this prototype came with a micro HDMI.  Luckily we had both spare cables sitting around, so no problem there.

The other side takes SD cards and the remote control.  Nothing too exciting over here.

On the top of the camera there's a lock button at the center of the mode dial.  This is something I wish my Canon 5DmII had come with.  Otherwise it's just standard controls as you would expect from any DSLR style camera.

The back screen is a nice flip-out LCD with plenty of features available in the menu.  I have the histogram shown here, but there's also focus peaking available...which even the 1DC lacks!  It's about damn time!  Also the new auto-focus feature is fast and smooth.  I plan to fully utilize it tomorrow since we didn't have a practical way of rigging a remote follow focus and remote monitoring for my AC.  From what little I've used it I was really impressed.  We're using the new auto-focus along with the 12-35 OIS f/2.8 Panasonic lens, for maximum micro-vibration control on the handheld rig.

One thing I wish they had an option for is a variable ND sort of like the Red Motion Mount.  Tomorrow I have to ride an external variable-ND filter to maintain proper exposure.  What I'm a bit concerned about are flare issues, especially in the sunny desert.  We'll just have to deal with that as it comes.

One control feature I really like is the control over highlights and shadows right in the camera.  On my Canon 5D all I get is the basic contrast control, which often gets set as low as it goes.  On here, if I have a shadow or highlight problem I can deal with it before the footage gets compressed to 8-bit 4:2:0 H.264 (in C4K).

Overall, I'm exited to shoot with this camera.  It meets most of my needs for the shoot and I look forward to seeing how the 4k footage turns out.  We have a nice location picked out, but the Santa Ana winds are really going to kick our collective butts tomorrow.  I'll post the next portion of the review once we put the footage through post production.

Saturday, March 1, 2014

••◊ Roger Deakins' Favorite Scenes : The Shawshank Redemption and No Country For Old Men

On the eve of the 2014 Academy Awards I found this little gem of an NPR interview with Roger Deakins. Enjoy.