I think by now it is readily apparent to anyone who has been following my Blog for any period of time that I’m not sold on the large format sensor revolution for every application.
Don’t get me wrong – if you are making an indie film or shooting beauty shots of products in a controlled environment, there is something to be said for the shallow depth of field that can be achieved by using larger sensors (4/3″, S35 or full frame).
Having said that, the “shallow depth of field movement” as I refer to it, which started with the advent of the spinning ground glass adaptors which mounted stills lenses onto video cameras starting about 8 or so years ago, has overtaken all good sense. The search for a cinematic look has overridden best practices in video production.
I come from a live television background. Live sports, news… that sort of thing. I also specialize in multicamera live switched environments such as conferences and conventions.
Our “Gold Standard” is 2/3″ chip cameras.
Pretty simple, actually.
2/3″ is derived from the old 16mm film days, which is how events were captured for playback after the fact until the “portable” VTR and camera combo was created. It is a great balance of image quality, light sensitivity and power considerations.
As well, lenses for these cameras have existed for quite some time that meet the requirements for live use:
- parfocal – lenses maintain focus throughout their zoom range.
- servo zoom – a small electric motor with precise speed control is used to drive the zoom mechanism.
- fast – maximum aperture on most 2/3″ zoom lenses is under F2 and very little light is lost as one moves toward a telephoto lens position, depending on the overall zoom factor
- large zoom factor – even short zoom lenses often offer 16x or more of zoom, with the most notable exceptions being wide angle zooms. In fact, some “box lenses” offer zoom factors in excess of 100x without engaging the 2x optical “doubler”. For example, this Fujinon zoom lens has a maximum focal length of 900mm without the doubler. In reference to Full Frame 35mm, this lens would be equivalent to a 3600mm lens. At 900mm, this lens maintains F4.7. Try that with a S35 lens.
- standard bayonet mount – virtually all 2/3″ zoom lenses use the same standard bayonet mount, allowing for virtually seamless ability to interchange lenses and cameras. There are some differences in the electronic matings of lenses and cameras but that discussion is beyond the scope of this discussion.
- back focus adjustment – virtually all lenses at this end of the spectrum all have an adjustment to compensate for the minute differences in manufacturing tolerances and differences that ambient temperature can have on the materials both the lens and camera mounting hardware are made of.
A recent forum thread I have weighed in on has a proponent suggesting that 2/3″ is dead and that with the advent of more cost effective S35 (or larger) ciné cameras, the move will be toward large format imagers in cameras aimed at live television and event video production. The truth is that ciné and stills lenses are built for very different purposes than ENG/EFP/Studio lenses. Even ciné zooms are typically much shorter in zoom factor and cost a great deal more in most cases.
Which is not to say that an Angenieux Optimo 28-340 isn’t a STUNNING lens; it is… it is just engineered for a different purpose altogether. And at $70k, it is still “only” a 12x zoom.
The bane of stills lenses for video production IMHO is that very few lenses are parfocal – by which I mean most stills lenses do not maintain focus throughout their zoom range.
What a number of camera/lens manufacturers are doing these days is introducing a Look Up Table (LUT) that alters the back focus of a lens “on the fly” relative to its focal length (zoom position). This is being done with varying degrees of success, depending largely on the size of the image sensor the lens is designed for.
JVC has added the functionality to its HM600 and HM650 “twins” which are industry leading in their zoom factors on small imager/form factor cameras. These are 1/3″ 3-chip cameras with 23x optical zoom lenses. At NAB 2012, the prototype was hand-carried to the show floor and exhibited what I considered to be unacceptable “hunting” for back focus as the lens focal length was changed.
This year, I spent a significant amount of time at the JVC booth trying to force the lens to “fail” to track back focus. I was not able to.
Contrast that result with a much anticipated servo zoom for an S35 sensor that a rival camera company was exhibiting. The 18 – 200 servo zoom exhibited a great deal of “hunting” as I used the servo motor drive to change focal length of the lens, causing the focus to drift in and out, regardless of whether it was a fast or slow zoom. Again, this is a S35 lens.
Does that make the 18 – 200 servo a bad lens?
Hardly! It just limits the usefulness of it to non-live zooms.
Horses for courses.
Finally, there is no definitive standard mount for these stills lenses that are being used with ever increasing frequency on video or digital cinema cameras. Whether Canon EF, Nikon F, 4/3″, PL, OCT-19 or Alpha, most practitioners are adapting their lenses to the mount on their cameras.
Remember when I talked above about broadcast zoom lenses having back focus adjustment? Stills lenses almost exclusively do not. They were/are designed to be used on the cameras that sport the mount that they were designed for. Several manufacturers of varying Quality Assurance and manufacturing tolerances are manufacturing adaptors, with varying degrees of success. Some end users are complaining about mounts flexing under weight or use, others are noting sections of the focal length and/or focal distance range have become unusable, especially with zoom lenses.
These lenses were never designed to be used the way they are being used.
Don’t get me wrong – lots of folks are getting great results with stills lenses, new and old, on their dSLRs and S35 digital ciné cameras. Just don’t expect every lens to work flawlessly with every adaptor on every camera.
I have mentioned that a good friend of mine operates an Indie-friendly ciné rental house. I spend a lot of time there. It never ceases to amaze me just how frequently DoPs and cinematographers mix and match lenses on their projects. Not just zooms and primes, but manufacturers as well.
Ciné lens manufacturers spend a lot of time, effort and resources to “match” lenses for colour, clarity and other characteristics within a given line of lenses so that the appropriate lens can be used to get the image required “on the day” but also so that the image will match that of every other lens in the line.
Stills lens manufacturers have built lenses to differing specifications over the years to meet differing requirements. A “portrait” lens will have differing characteristics than a “copy” or medical imaging lens. Mixing and matching without knowing what that classic Nikon prime was originally intended for is a recipe for disaster.
Most new practitioners (and some aging folk who never learned better) select lenses based on very simple criteria: focal length and maximum aperture.
There is so much more to imaging than that.
<steps off soapbox>
Thanks for reading!