Camera lenses: An optical crisis
Quality lenses have never been more necessary or in greater demand. With resolutions beyond 4000 horizontal pixels now common, and an explosion in the availability of cheap, big-chip cameras since the mid-2000s, the value of even quite average glass has rocketed to the point where anyone who bought a fairly everyday set of 1970s Russian movie primes at that time will be extremely pleased with the decision to do so.
Anyone who didn't make that sort of call, however, would be forgiven for interpreting the massive mismatch that currently exists between the price-performance ratio of cameras, and the price-performance ratio of lenses, as something of a crisis. This is not a new observation – in fact, it's been an issue for anything up to a decade. Even so, lens availability is a problem that's still only been partially solved.
In some situations, stills lenses can be pressed into service – endless short films and music videos are shot on Canon's EF series all over the world, and the company celebrated shipping its hundred millionth EF lens earlier this year. Beyond that, Samyang has produced its VDSLR range. These offer full manual control, perhaps a recognition of the the issues of ergonomics and controllability with affordable stills lenses. While these lenses lack some of the refinements of high-end cine lenses, such as consistent physical dimensions and minimum aperture, they go a long way to solving the lens crisis for the right kind of shoot.
The next option up is either directly modified stills lenses from various companies, which tend to be expensive, or something like Schneider's Cine-Xenar III or Xenon FF ranges. These offer superb capability, but at a cost that makes them meaningless to people on a DSLR budget. I'm surprised there aren't already more competitors in the U$1000-a-set movie lens market, but it is at least a market that is recognised to exist and is being served.
The unsolved problem, then, is documentary and ENG (electronic news gathering) style shooting. This covers anything from corporate and industrial to weddings and the sort of travel or nature observational work where there's a need for a camera system that's compact and easy to transport. Traditionally, this sort of work was almost entirely done on ENG-style cameras with B4-mount broadcast lenses from Canon or Fujinon, which is not something that has a low-cost equivalent in the way that Samyang's VDSLR range is a low-cost version of an Arri Master Prime. At the same time, it's gradually being realised, in at least some fields, that things like Blackmagic's Cinema Camera and the better DSLRs, such as the Panasonic GH4 and Sony's new Alpha 7S, are starting to make somewhat competitive pictures for considerably less money than extant full size shoulder-mount offerings.
The crucial issue is that none of the extant lens options really work well in this sort of scenario. Stills zooms are a miserable experience for the ENG-trained operator, with incredibly short and invariably non-indexed focus throw, often completely absent iris control, no really wide angle available, no convenient grip for servo zoom control and easy handling, and other problems. Stills lenses are, in general, both cheaper and sharper than the broadcast zooms that were once used in this field, but the ergonomic and operational tradeoff is horrendous.
There is only one off-the-shelf ENG-style lens for single-chip camera, as far as I'm aware: Fujinon's Cabrio 19-90 zoom (and perhaps its longer-focal-length brother), which is essentially a cross between an ENG zoom and a movie prime, designed to suit PL-mount cameras with 35mm-sized imagers. There are problems, including the relatively limited focal length range and the weight, but the biggest issue is the price. At the best part of US$40,000, they'll doubtless be found on a lot of Arri Amiras, but this is not a meaningful option to the sort of people who are working with products from Blackmagic or Canon products.
All of this begs the question: can we apply comparatively affordable, capable B4-mount broadcast lenses to affordable, capable single-chip cameras? Well, possibly. Various types of mount adaptor exist to take us from B4 lenses to shallow mounts such as micro four-thirds and Sony's E and A mounts. The principal obstacle is that these lenses are intended to project an image onto the 2/3” 3-chip imager of an ENG camera, and will vignette on anything with a larger sensor.
This is not the end of the world; the ETC mode in a Panasonic GH-series stills camera produces an effective sensor similar in size to that of a 2/3” camera, and better B4 lenses have an optical extender which is intended to double the effective focal length (at the cost of some light) but has the incidental effect of doubling the size of the projected image, too. Blackmagic's original camera, and its pocket-sized cousin, don't have particularly big sensors and can be used in this configuration.
The principal concern is one of optical quality. Let's assume we're happy with the performance of modern HD broadcast lenses on their native cameras – we should be clear here that older, physically compatible B4-mount zooms intended for SD work often lack the resolving power to satisfy HD cameras regardless of other considerations. The second, trickier issue is that B4 lenses are configured to land their images on the three separate sensors of a broadcast camera, can reportedly produce strange phenomena of defocussed colour and fringing when used on a single-chip camera. Many online examples fail to demonstrate this problem because they are often done with old standard-definition lenses which simply aren't sharp enough to reveal the issue, but the problem doesn't appear to be absolutely crippling.
In any case, there's a solution: IB/E Optics has produced a range of adaptors (principally the HDx35) with optical correction for both coverage up to 35mm size and to correct 3-chip alignment problems. At US$4800 or so just for the adaptor, it's not a low-cost option, but mid-budget people might consider it interesting that, alongside the US$10,000 for something like a Fujinon 17x7.6 HD zoom, it creates a system well under half the price of the 19-90 Cabrio with considerable extra flexibility (though doubtless lower optical quality). To go even cheaper, probably at the cost of some more image quality, a simple mount adaptor can be had for a few hundred dollars, although at that point careful coverage and sharpness evaluation of potential lenses would seem in order.
We can only hope that less expensive and awkward solutions become available. It seems reasonable to anticipate that single-chip ENG-style cameras will start to become normal as sensor manufacturing capability improves, because there is no real technical reason to stick with the three-chip layout other than, ironically, lens compatibility. It's also reasonable to theorise that Canon and Fujinon might start to produce more affordable ENG-style lenses to suit. After all, the optical correction for the three-chip imager implies more lens elements, and thus more bulk and cost and a reduction in image quality. Solving the lens problem for DSLR documentarians seems like a no-lose proposition; the problem, as ever, is chicken and egg.