Why choose a cinema lens?
Often, well sometimes, a cinema lens is identical in optical design to a stills lens from the same maker (Sony, IRIX, Sigma), but it is physically different and must fall within the parameters needed to make a cinema grade lens.
Thjis can mean different things to different people and there are ‘camps” of preferences in this field, but there also some constants.
A cine lens will have longer focus throw, smooth manual focus, manual and step-less aperture ring, consistent body shape and size (for rigging) and more often than not be at least 50% dearer.
Two 25mm lenses for the same format. One is designed for maximum edge to edge sharpness, high contrast and “modern” stills rendering while being auto everything. The other is designed for manual handling and things that look good, sometimes even when they are considered flaws or some older fashioned things like the 3D effect, deeper depth of field Bokeh, as well as the first thing you would grab in a fight. The smaller lens is also brighter in aperture.
What else do you need to think about, what is the actual difference?
Sharpness and contrast.
Cinema lenses, against current opinion, do need to be sharp, but they do not need to be photography or “perfectly” sharp, which is to say razor sharp edge to edge with biting contrast.
“Character” a term often used to hide unacceptable flaws in stills lenses are sometimes fostered in cinema lenses, even the dearest ones, because unlike stills, moving footage looks more natural with some softness or smoothness.
All these characteristics however, need to contribute the overall viewing experience.
Smoothness can be from the lens, the frame rate, lighting, filtering or motion blur. Even the old enemies of chromatic aberration are seen as “additives”.
The question you must ask yourself when choosing a cine lens, dear or cheap, old or new is “do I like the rendering?”. This is something you have to deal with at your end, visually, instinctively. Ignore the price tag, ignore the reputation and the test charts, just look at the results (in context).
There is a reason quite ancient legacy glass is used on some big production movies. It is not simple perfection they seek.
Bokeh.
Sharpness or the perception of it’s qualities often goes hand in hand with Bokeh or the subjective quality of out of focus elements, which is a thing at any aperture as long as there is even a small amount of focus transition.
The cinematic look generally includes some out of focus areas, areas that become as much a part of the image as the sharp parts, so the quality of that blurring cannot be avoided. Super shallow depth is rarely used in cinema except in extreme cases, so Bokeh at a more useable aperture like f4 on a full frame has to be taken into account.
Modern “perfect” glass comes at a price. The super soft Bokeh rendering of the latest Sigma or Sony G-master is nice if you need it, but from a cinematographers perspective, it may be too aggressive, too “perfect”, rarely applicable and lack a transitional or interest value beloved by the masters.
Like above, you need to see it in action and go with your heart and gut.
Three dimensionality.
A modern trend with super corrected still lenses is a “flatness” in rendering. This is always common in longer lenses to some degree, but seeking technical perfection in other spheres seems to exaggerate it. It is almost a blind spot fostered by recent designers, needed for them to deliver more fashionable qualities like resolution.
Like Bokeh above, three dimensionality and blur character are all part of the rendering of the frame, which may, against modern trends, need some interplay of depth. The whole moving frame will be visible for the whole time, so how that works with the blocking of the characters is critical to good videography. The sharp/soft look, so good at softening a background to make a blogger look good may not work to tell a story.
Flare.
Flare is subjective as are most of the things we are dealing with are, but it is something you need to be aware of because situations where it may be a factor are virtually guaranteed.
many like some flare, Saving Private Ryan was filmed with lenses that were deliberately uncoated to exaggerate flare like older lenses, but too much or ugly flare simply ruins a shot.
Lenses will flare, but you need to be aware of how much, what type and whether it enhances the frame or ruins it for your vision.
This is a tough one, but thankfully many reviewers touch on this enough to get you part of the way there.
So, you need to like the sharpness, Bokeh, flare and 3d rendering of your lens.
Distortions.
Often tested to ridiculous extent and often corrected in camera by paranoid manufacturers, distortions are many and varied. In cinema, thanks mostly to older anamorphic lenses used warts-and-all in many big budget movies by choice, distortions are not only tolerated, but often pursued.
Wes Anderson uses wide shots often with centred subjects. Take a scene from his movies, any scene really and look at the horizontals and edge sharpness. You will see bad things there, unacceptable to most stills shooters.
Not an architectural photographers dream, Anderson seems to also want to exaggerate this by his subject placement.
Handling.
Cine lenses are designed for use in heavy cinema rigs using focus pulling gears etc. It is important that this is recognised, because just buying one for hand held work may not be ideal. Talking from personal experience, some of my cine lenses feel good and work fine as hand held lenses (Hope 25, Sirui 24, Spectrum 50 ), while some are not as sweet.
They have by nature long focus throw, which for fast work can be annoying, but is ideal for more measured work.
Equally, I enjoy many stills lenses for fast work, but the opposite is not true on the whole. When using stills lenses in a cine role, they are inconsistent and twitchy, often too small, lack focussing aids and aperture changes are “clicked”, even when electronically applied. I can use Pana lenses on Pana cams with electronically applied longer throw, which helps a little.
Cine lenses are usually mechanically matched, making rigging easy. No need to shift follow focus rings etc and weight can be similar. (see below).
Focus Breathing.
This is irrelevant in stills work, but important for focus transitions in video. Does the lens “shift” framing when focus is pulled a lot. This may not be a huge thing for you, but it may be.
Consistency.
Cine lenses are meant to be able to be used in matched sets. This is rare, even with dearer sets of lenses, but the closer the better. Colour matching (warm or cool), rendering (sharpness, Bokeh, flare etc), mechanical placement of focus and aperture rings etc, should all be at least within the same ball park.
Even some cheap sets are close here (4 out of the 6 Hope lenses match well, two are slightly warmer or cooler). Interestingly, even some dearer sets are not perfect.
I have actually mixed sets and brands with little issue after painstaking research and have a simple system of stickers (blue/white/yellow) to help remind me of warm or cool sensor and lens combinations (regardless of lens consistency, even cameras from the same maker can vary).
It can be a matter of buy what you like and see what works or be more scientific, research well and make your choice.
Do you need a cine lens?
To be honest, my full frame kit is well served by the Lumix-S primes, which have many of the benefits of a cine set (same filter, same overall size and similar weight, linear focus throw-on a Pana cam). They are light, reasonably priced and have a nice balance of sharp/smooth rendering, with well controlled focus breathing.
In M43, it is the opposite. The Hope lenses are great value cine glass and my cherry picked extras, the Sirui 24 Nightwalker and Vision 12mm match adequately. The odd AF zoom pops up when AF is needed, but I generally do not. In another life, one where I would only have M43 format, I would have bought the two Pana f1.7 zooms, but that is another life.