Film, Video, and 35mm Lens Adapters
"How do I make video look like film?" This seemingly innocent question can provoke some of the most heated arguments you'll ever overhear between professionals. Technically speaking, there are a number of distinctions between the formats, some of which can be negated by today's crop of camcorders that offer increased dynamic range, better color and gamma controls—and, of course—high-resolution 24fps progressive imagers. But it is more than a technical issue. Speaking aesthetically, feature films are generally lit with care by professionals, and then edited and tweaked for months in post production. Perhaps the best answer to the question above is simply: "With a sizable budget."
One way to approximate the look of film more closely is to use selective focus and shallow depth-of-field (DOF) in your compositions. In simple terms, DOF is the plane in an image that is within the range of acceptable focus. A shallow DOF would be indicated by a very narrow plane of focus within this range. Conversely, wide DOF is indicated by much of the scene being in focus (think "Citizen Kane"). Today's affordable HD cameras all use relatively small sensors to capture images, and depth-of-field is directly related to the size of the imager in a camera: a 1/3" sensor-equipped HDV camcorder is going to exhibit wide DOF, and a 2/3" high-end broadcast camera will have a much shallower DOF. Step up to a high-end Digital Cinema Camera (video camera) like the Arri D20, Panavision Genesis, and Red One, which all offer 35mm-sized imagers, and the DOF becomes even shallower (on par with a film camera). As you step up in price in video cameras, you effectively gain more and more control over focus in your images. This generates an unfortunate side effect for shooters like me who depend primarily on affordable small-format HD cameras for much of our work, but crave more control over focus. The answer for me, and many other filmmakers, lies in 35mm adapters.
What is a 35mm Lens Adapter?
A 35mm Lens Adapter mounts to the front of a video camera; the forward element of the lens adapter system includes a lens mount that accepts common 35mm still-camera lenses. These low-cost manual lenses are readily available and offer essentially the same image characteristics as a 35mm cinema lens. Most adapters also offer the option to step up to a PL-mount for cinema lenses. I'll explain why you might want to consider this, in a moment. In simple terms, the light from the 35mm lens is projected onto an imaging plane in the adapter. This plane is generally referred to as the "ground glass," a semi-transparent textured imaging element that is either spun or oscillated in a random fashion. At the other end of the adapter, the video camera is zoomed in to frame within the inside edges of the imaging element. Optics in the 35mm adapter system help video cameras achieve this close macro focus on the imaging element. Focus on the video camera is then locked at that plane, which becomes the back focus for the entire system. Once the adapter and lens are seated, all image focus is controlled at the 35mm lens itself. For this reason, you must use manual-style lenses with 35mm adapters. There are no electronics to drive autofocus, so all focus control happens at the manual focus ring on the 35mm lens, and f-stops are set with the aperture ring.
There are numerous reasons to shoot with 35mm lens adapters, such as the power to achieve far shallower DOF. Another less-cited reason is that most adapters soften the image just a touch; they can remove some of the harshness of HD video. But by far, my favorite reason for the use of 35mm adapters is the fact that they tend to make you work more in the "film style," slowing down your work flow and compelling you to pay closer attention to framing and composition. Because focus is a critical element with a 35mm adapter rig, you tend to work more with your talent and skill—and it makes you a better director. Speaking personally, for example, shooting with an adapter has made me more aware of lighting. Residual effects such as these can have an extremely positive effect on your filmmaking.
I've been shooting with the Brevis35 adapter from Cinevate for about a year. The Brevis offers a unique modular design that is very attractive to me from a reliability perspective. When Brevis introduced a flip unit recently (I've been shooting with the pre-flip version that records an inverted image), because of its modularity, it was a simple task to attach the new flip unit to the Brevis imaging tube and start shooting. I've also observed in another review that the flip unit has improved the optics of the system and delivers better sharpness overall. A modular design means that seasoned Brevis owners don't get left out in the cold, and I appreciate that. Another one of the reasons I chose this system was because of its low-light performance; there is an inherent loss of light in every adapter on the market, and the Brevis is one of the brightest options available. This was important for my work flow, since I don't always have time to illuminate a shoot with 2500 watts of light. The sensitivity of the Brevis system allows me a little more latitude with simple light sources, and to take advantage of low-wattage sources, natural light, and lightweight bounce solutions.
Brevis Design and Construction
The Cinevate Brevis 35mm adapter system is beautifully engineered. I admit that I've always been a fan of the design and construction of its gear. The Brevis is composed of a mix of milled aluminum and carbon fiber. Metal surfaces are powder-coated with an optical flat black finish, and I was informed recently that Cinevate is introducing surface-hardened anodizing as the standard finish. All the major components of the system can be broken down at all their major connection points for storage, transport, or repair. There is enough adjustment built into the design to allow the system to be tweaked to deal with a variety of video cameras. I've personally shot with the Brevis on Sony HDV cameras, the new XDCAM PMW-EX1, and the Panasonic AG-HVX200. I'm told that the system works especially well with the very sharp Canon XH-A1 HDV camcorder. The bottom line is that once you've set up the system on one camera, it is a relatively simple task to learn how to set it up on another camera.
Brevis Imaging Elements
I mentioned the modularity of the system: Cinevate has engineered a unique design feature that allows users to swap out the internal imaging elements to "tune" the adapter to the needs of specific projects. These are called "Cinefuse" elements. Cinevate offers six discrete elements that can be used in the Brevis. Cameras equipped with filter threads smaller than 58mm should use the CF1, CF2, or CF3 elements. Larger cameras with filter threads greater than 62mm tend to perform better with the CF1Le, CF2Le, and CF3Le options. The "Le" designated diffusers are tuned to deliver better edge sharpness and reduced vignetting across the typical lens range. The "Le" series delivers better vignetting performance on cheap and slow wide lenses (typically, wide lenses tend to have lighter fall-off, and therefore can cause image vignetting).
Each Cinefuse option contributes a different look to the image, particularly the rounded, out-of-focus specular highlights in the frame ("bokeh"). Essentially, the CF1 elements offer the least diffused bokeh. They are the most light-efficient option and are therefore considered a good choice for general-purpose production work. I use them, primarily. The CF2 series of elements offers higher levels of bokeh diffusion over CF1 at the expense of an additional half stop of light. CF3 increases the background diffusion even more over CF2, and of course has a bit more light loss. CF3 is generally regarded by users as creating the most filmic image of Cinefuse options. Speaking personally, CF3 is a bit too diffused for my tastes (to be appropriate for most projects). Opening up the Brevis and swapping a Cinefuse diffuser is a relatively straightforward task that can be accomplished in about 5 minutes, with some practice. The fact that you can change the essential characteristics of your 35mm adapter image with a simple element swap is one of the characteristics of the Brevis adapter that I find most attractive.
Brevis Image Performance
One of the real side effects of shooting with a 35mm adapter is the slight loss in image sharpness. Depending on what you are shooting, this can be highly desirable—or a major concern. Some users believe that the softening effect is one of the major reasons that adapter footage looks so different than straight video. Others want to eke every little bit of sharpness and resolution out of their image work flow. I tend to stand somewhere in the middle of that argument. It's interesting to note that sharpness is never perfectly consistent across the frame of any 35mm adapter. I know because I've tested most of them. Some designs show significant decreases in resolution on the edges and in corners of the frame. The same is true of chromatic aberration and fringing artifacts; these issues tend to be more obvious on the edges. I recently tested the Brevis35 Flip with a Sony XDCAM PMW-EX1, one of the sharpest new camcorders on the market. I found that when optimally configured, the EX1 and Brevis deliver about 700 Vertical and 700 Horizontal lines of resolution. The image appears crisp up into the low 900's. As is always the case with adding an adapter, chromatic aberration and fringing are slightly more pronounced than with the stock camera lens by itself. Image far-corner and edge sharpness drops a bit, but remains well within reasonable limits, and is discernibly crisp past 725 lines.
Many Brevis owners have noted that the Brevis design has a non-linear response to lenses and light. This appears to be unique to the Brevis design. What this means is that the image recorded on the camcorder does not seem to "get brighter" when you open the aperture of the lens wider than about f/2.8. So if you have the 35mm lens set to f/5.6 and open it up to f/4, you will see a change in light: the image becomes brighter. But this is not true when opening up the lens from, say, f/2.8 to f/2 (or f/1.4 for that matter). The bottom line is that the Brevis is as bright at f/2.8 as it will be at f/1.4. Some suggest that this means the Brevis is "blind" to light from apertures wider than f/2.8. Others think that there is a "set gain" in the adapter system. I frankly don't have a solid handle on the nuances of this issue beyond being able to confirm the behavior noted above. It has both positive and negative ramifications. On the positive, there is less of an incentive to shoot with the lens at f/1.8; your image is nearly as bright at f/4—which is more in the sharp "sweet spot" of most 35mm lenses. The negative side is that it behaves in a non-linear fashion that is totally going to throw off a DP or gaffer that is used to lighting a set with a light meter. This is less and less of an issue in today's digital world where many professionals light by eye anyway, but it is still an important one to note.
The Brevis has been a reliable performer for me. It is well suited to a wide variety of small-format HD camcorders, and really excels on the extremely sharp Sony PMW-EX1. The unit is lightweight yet strong, and offers well over 20 hours of rechargeable battery life. Since the battery is of the non-removable, internal variety, I would recommend picking up Cinevate's emergency field power adapter that allows you to use AA batteries in a pinch (this, quite frankly, should be standard equipment). Image quality and sharpness is very good, as 35mm adapters go. The non-linear light response is an odd behavior of the unit, but has not posed a major issue, in my personal experience. Your mileage may vary, of course. Setup and configuration of the system is relatively simple, and the modular design of the entire system is a very strong point, in my opinion. Overall, Cinevate's 35mm adapter system is a competent performer that has served me well.
If you are looking for more information on this system, including charts and raw data on image performance, I've written an extensive short article series at www.freshdv.com.
Matthew Jeppsen is a freelance HD shooter and editor. He writes about today's tools and techniques at www.freshdv.com.
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