It's been one of my pet peeves ever since the advent of digital cinema cameras: at the same frame rate and shutter speed as a film camera, digital sensors looks more stroboscopic. There's more jutter and I find it distracting. For a long time I couldn't explain what I was seeing until Adam Wilt explained why in a piece about RED. Now Adam's the first to bring my attention to a new product called a Time Filter from Tessive. If you want a smoother shutter rendering on your digital footage, this is a serious innovation -- brilliant, in my opinion.
At the standard shutter speed of 1/48th of a second on a 24p shoot, digital cameras have motion rendering that bothers me as too stroboscopic. See if you can spot the difference in these two shots:
So what's the difference between digital and film cameras in this regard? Once again I'll turn it over to Adam:
Film cameras usually use a mechanical shutter at some distance from the film plane; their shutters do not sharply and suddenly expose and then cover the film, but perform a soft-edged, “fade-in, fade-out” exposure due to their defocused, penumbral sweep across any given point on the film plane. 24p digital cameras with 180-degree shutters (or 1/48 sec shutters, if you prefer) tend to show more visible “stuttering” or “judder” on motion than film cameras do with the same shutter angle or time; the sharp-edged motion blur is the culprit. Some shooters try to compensate by opening the shutter longer, say, to 1/32 sec or 270 degrees. This increases the blur duration, partially (but only partially) compensating for the sharp edges, at the expense of increased blur overall.
I've experimented with slower shutter speeds in the past, and it works pretty well on many shots. But I get the feeling the difference is more pronounced for me than it is for most. Maybe I just have sensitive eyes. But I also think part of the magical nature of 24 FPS film is the smooth, penumbral motion rendering, and that has been lost with the switch to digital cameras. From their tests, it seems that the Tessive Time Filter brings it back. Here's how it works:
Yes, it's a drop-in matte box filter. Brilliant. Okay, so if this thing is so great, why aren't we all using it right now? Drawbacks include a loss of two stops of exposure (though with today's super-sensitive 800 ISO cameras, some might embrace this exposure loss), and you need a genlockable camera -- a DSLR won't work. Oh, and this first version costs $14k. Check out Adam's full article below (it's tucked into a post about Cine Gear, about which I'll have more soon), which is a must-read for camera nerds.
Tessive was demonstrating the Time Filter at this year's Cine Gear, and while I'm far less concerned with wagon wheels turning backwards -- I'm chiefly interested in the motion rendering on everyday shots -- FreshDV got a nice demo from them, which shows that not only does the Time Filter demonstrate better motion rendering but in fact eliminates rolling shutter problems, because it's effectively a mechanical shutter:
At $14k you're not going to be buying one of these unless you're a rental house, but that's exactly what it's designed for: renting. My own forthcoming feature is going to have a very active camera (at times), and I'd love to get a more filmic motion rendering without the drastically increased (and unrealistic) budget that would come with shooting on film. Great work, Tessive.
Links:
- Tessive
- Cine Gear Expo LA 2011 - Adam Wilt
