Tag: optics

Photography offers a moment of interest. Cinema demands sustained attention

I get a lot of emails and calls from customers asking what kind of lens package they should get for their shiny new Sony F3 or their tiny new RED Epic. The simple answer is, there is no simple answer. Let’s face it, for most of us who aren’t shooting the next Iron Man feature film, budget is the primary factor when it comes to choosing a lens package. A lot of folks who would be looking for a new lens kit are coming over from the still photo world. As you all know, the RED/DSLR revolution has changed the industry drastically over the past few years and allowed a lot of people to squeak by with existing gear or pre-owned gear that got the job done. Maybe now it’s time to step-up your game and get a set of true cinema lenses. Or maybe it’s time to snatch up some glass/metal tubes from Russia that Ivan tried to pass of as a cinema lens… Either way, what’s the difference between a 18-55mm Nikon kit lens ($90) and an exotic Angenieux 24-290mm Optimo ($70,000)?

Basically, everything boils down to two categories; usability and image quality. Obviously there are other factors involved such as production quantity, but that is usually tied into image quality.  Again, the question is, why is a cinema lens so much more expensive than a still photo lens? Cinema lens prices increase exponentially as the quality increases. For this demonstration, the top of the price spectrum will be represented by the Angenieux 24-290mm Optimo, and the bottom will be represented by the Nikon 18-55mm kit lens. Some would expect a few test shots with some text overlaid on them similar to that of most online lens reviews (mine included), but this really doesn’t show much beyond very basic image quality. To be honest, with todays manufacturing processes and techniques, the overall image quality in the center portion of each example lens, would probably be fairly similar. That doesn’t mean that the next big feature film is going to go out and shoot on a Nikon 18-55mm, but it also doesn’t mean that an 18-55mm Nikon isn’t going to produce good results. This is where the usability of each lens comes into play. For example, the entire core, focus, zoom, lock rings, and housing of the 24-290mm Optimo are machined from billet aluminum. The only part of the Optimo that isn’t made of high quality aluminum is the mount… Because that is made of stainless steel. Comparatively, the Nikon 18-55mm does in fact have an aluminum core, but everything else is plastic and brass, which can be good. It keeps weight and production cost down to a minimum, but is devastating to mechanical accuracy and precision. It doesn’t mean that the Optimo is the better lens for every situation. I wouldn’t want to lug a 25 lb. lens around Disneyland to snap pics of the family with Mickey Mouse. This leads me to the fine details such as stability and accuracy. Cinema lenses are not auto focus and traditionally require a trained focus puller to nail focus in any given shot. This isn’t done by peering through the viewfinder or pressing a button. It’s accomplished by taping out the distance to the subject and then dialing in the measured distance on the lens’ focus scale, which means those marks better be accurate or someone is losing their job. Focus mark accuracy isn’t really a concern on still photo lenses since 99% of users simply depress the shutter button half way and let the cameras auto focus do the work. The other 1% of users who focus manually for still photography, usually look through the viewfinder, pick a subject and adjust the focus ring until it looks sharp, still no need for focus mark accuracy. Nobody sets up their SLR, tapes out the distance, adjusts the lens to that distance and snaps away. It’s just to realistic.

Speaking of focus, image shift and breathing are two more features that are critical in motion picture lenses, but not so much in still photo lenses. Let’s take our 18-55mm Nikon lens, put it on a camera, look through the monitor and rack focus or zoom. The whole image jumps around and loses focus because the components used inside the lens are very light-duty and left very loose to allow the tiny little drive motors to auto focus the lens for you. Comparatively, our 24-290mm Optimo is built with solid aluminum components that are precisely fitted and adjusted to keep everything as tight as possible. This keeps everything extremely smooth and accurate. If you adjust focus or zoom, the image should stay dead center and solid. This kind of performance requires extremely tight tolerances during machining and a very high level of care during assembly. Focusing with just about any still photo zoom lens will create a “breathing” effect that is simply an optical design characteristic. There is no adjustment for this flaw within the lens. It’s part of the optical-mechanical design and is taken into consideration during the development of a lens. Breathing is a bad thing in cinema because it really pulls the audience out of the scene. It changes the field of view of the lens and appears as though the lens is zooming in and out during even a small focus pull. This is why cinema lenses are designed not to breath and add substantially to the cost in order to do so. Tracking is somewhat related to breathing as it can really ruin ascot if not calibrate. Tracking is the movement of the image relative the the sensor/film, while zooming. Ideally, zoomed all the way in, an object in the very center of the image should stay in the exact same position on the sensor/film throughout the entire zoom range. Most cinema lenses include internal adjustment to calibrate tracking while still photo lenses aren’t concerned since you can simply re-compose before each shot.

Another common characteristic of still photo zooms is their speed, or maximum aperture. Take our 18-55mm Nikon for example, again… The maximum aperture is f/3.5 which isn’t too bad. But as soon as you start to zoom, it looses light and stops all the way down to an f/5.6. Modern SLR cameras can easily compensate for this with automatic adjustments to exposure with the shutter speed or ISO. The 24-290mm is comparatively very fast at T2.8 and maintains its maximum aperture throughout it’s entire zoom range. Mostly because it’s an annoyance to think about adjusting setting from shot to shot and trying to match everything, but also because it would look horrible if the aperture started to close down in the middle of a shot, ruining the lighting, look and feel of a scene. Okay, there are plenty of still photo lenses that maintain a constant aperture. In fact, most of the major pro lenses will do this easily. But these are usually a fairly short zoom range. Do the numbers… Take the 14-24mm Nikkor, a great lens with a constant f/2.8 aperture, the zoom range is only 1.7x. The 24-70mm, a 2.9x. And the 70-200mm, a 2.8x zoom. Those three lenses are Nikons current crop of pro zoom lenses. The Angenieux 24-290mm maintains the same constant T2.8 aperture throughout it’s 12x zoom range. That’s almost unheard of in still photo lenses. These couple of characteristics can be lumped into the optical quality of the lens but also effect the usability. Another usability concern for motion picture lenses is their durability. Granted, if a cinema lens is dropped, it’s almost certain that it’s thrown completely out of whack and would require re-calibration, they are built like tanks. The same can not be said for our little 18-55mm Nikon friend. However, there are a lot of modern still photo lenses that are built to endure relentless usage and can really take a beating. All of these details are very minor on paper. It’s when you really get into the nitty gritty and use the lenses on a daily basis that you realize the differences can be substantial. Kind of like looking at two different cameras on paper. Each camera has a 3″ LCD screen, shutter speed, aperture, and ISO adjustments, an SD card slot, compact and portable, and includes a strap! One is a Leica, the other is a Kodak. Both are great cameras, but they are clearly meant for different purposes and clearly have a cost difference. The same logic applies to still photo lenses and cinema lenses. I like to think of it this way: Still photography offers a moment of interest. Cinema demands sustained attention.