August 8, 2016

Sometimes You Just Need to Rack Depth of Field—Now, There's a Way

Cinefade Master
If you want to rack just the depth of field (and not the exposure) there's finally a tool for that.

Many of our most useful inventions are just two other inventions smushed together. The clock radio, the spork, the beer hat, sometimes you've just got to take two great things and make them one.  

With the Cinefade, filmmaker Oliver Janesh Christiansen has combined two useful tools into one. He took the motor control for an aperture rack (built by cMotion), and a variable ND filter, gave it motor control, and synced them together. He thereby created a single tool designed to do an aperture rack, which changes the depth of field, and to counter that aperture rack with the ND filter to keep the exposure level constant.

Cinefade on a Red Epic
Cinefade set up on a Red Epic: note the cMotion controller synced with the ND variable lens control on top of the matte box.Credit: Cinefade

Of course, when you change the aperture on a lens, depth of field and exposure aren't the only items that change. If you are racking the aperture all the way to the outermost stops you might see a quality and sharpness change, and as you rack through the apertures, you are likely to see a contrast shift (and sometimes even a slight color shift). While these are quite subtle, I do notice a slight shift in image quality on the main subject's face (which should, in theory, remain constant and unchanged) in the demo video, in addition to an ever so slight exposure "bump" where it seems like the sync between the ND and the rack aren't perfect.

None of these are deal-breakers, however, with the bump being something you could easily smooth out in grading, and the image quality changes being very subtle. It's a very specialized tool that probably won't make it in the regular rotation, but I could see music videos and commercials taking putting it to good use, or even applications in narrative for "transition" moments for a character. It's also possible to conceive of uses other than "background" focus, like racking one of the characters in a two-shot in and out of focus, or bringing a foreground object into focus over the course of the scene.

Currently the item is for rent directly from CineFade, who are located in London but available for travel.  Hopefully if the system does well it'll be available from vendors in multiple regions, though it's likely to remain a rental-only item for most of us.

Technical Specs:

  • cMotion controller
  • ARRI motors
  • Custom motorized filter trailer
  • Formatt-Hitech Variable ND filter for high optical quality
  • 5 stop range

Your Comment

4 Comments

When I was first learning about depth of field and exposure I thought of this kind of shot, thinking I was a genius for inventing it. A little bit of google-ing set me straight, but very nice to see someone has made a precise, professional method of actually doing this.

I can think of a few scenes/moments where this technique could add to a story - and it's still up for grabs for some director to make it her signature shot!

August 8, 2016 at 11:51PM, Edited August 8, 11:52PM

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Shouldn't Sony's FS5 be able to do this with a software upgrade? Its built-in variable ND just needs to be mated with a lens with an electronic interface.

August 9, 2016 at 7:45AM

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Robert Jacobs
Proprietor, producer, director, cinematographer
88

Indeed it should, if they wanted to add the feature. It seems like much of the fly-by-wire gear out there could be implemented in a more effective manner.

August 9, 2016 at 12:17PM

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C'mon, might as well throw a hitchcock dolly-zoom in there while you're at it.

August 10, 2016 at 12:07AM

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