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.
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.
Video is no longer available: vimeo.com/117731707
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.
- cMotion controller
- ARRI motors
- Custom motorized filter trailer
- Formatt-Hitech Variable ND filter for high optical quality
- 5 stop range