What is the difference between a cine lens and regular lens?

Producing video with DSLRs is becoming more and more popular thanks to feature rich and affordable cameras making it more accessible. Many credit this trend to the popularity and robustness of the Canon 5D Mark III and even more so with the availability of Magic Lantern, a 3rd party firmware for Canon DSLRs. If you’re exploring video with a DSLR, you may have come across lenses labeled as cine lenses or a cine version of a lens. These lenses aren’t exclusive to DSLRs and actually originate in the film industry, but they’re also growing among DSLR users. 

What are they? What are the benefits?

Cine lenses are lenses designed for the video and film industry (no, not film photography). They’re usually much more expensive than regular lenses and at first glance, may appear to offer less, making the price tag hard to justify. The most obvious difference in these lenses is most lack a focus motor, making auto focus not an option. Many might think this isn’t worth the price if the lens can’t auto focus. However, professionals in the film industry rely on manual focus anyway. This allows for far better control over focus without relying on software to figure out what to focus on. Imagine filming a production with very specific shot lists with a change in focus at a specific moment. How would you control the change in focus? If you found a way, what if it focuses on the wrong subject? Manual focus ensures focus isn’t missed, the change is at a smooth and pleasing pace, and the moment it changes is precise. This leads me to the next point: since manual focus is the idea, the focus rings on cine lenses are usually very smooth and precise. The focus ring isn’t like most still lenses that rely on auto focus in which a slight rotation make a significant change in focus. 

Since we’re on the topic of focus, another benefit is that cine lenses don’t produce a phenomenon called focus breathing when focus is adjusted. Many still cameras produce this, but it’s subtle enough not to notice between photos. Focus breathing is when the focal length, or apparent zoom, of the lens shifts closer or further as the lens focuses. When this occurs, it’s so subtle that it’s almost impossible to notice. However, if a lens is continuously “breathing” in and out during a scene, the recording will capture it and it will be noticeable. This can be distracting to the audience in a production. Although this doesn’t occur in cine lenses, it also doesn’t occur in every regular lens. This is just a phenomenon that can be common with regular lenses and something to watch for. 

Another benefit to cine lenses is that they tend to have a “declicked” aperture ring. Aperture is usually also manual, but this is to provide full control to the photographer over exposure. However, the term “declicked” refers to the clicks in the aperture ring that set hard aperture sizes. For instance, a regular lens with manual aperture controls that is not declicked might offer f/2.8 on the wide end and turning the ring jumps right to f/3.5. There is no aperture in between f/2.8 and f/3.5, causing a sudden change in exposure rather than a gradual one. With a declicked aperture ring, the photographer can go from f/2.8 to f/3.5 as slowly as he or she wants without a sudden jump. The photographer could even stop at f/3.125 if desired. The benefit to this is video can produce smooth transitions in exposure when necessary without a jarring, sudden change in exposure. 

Lastly, cine lenses usually measure their light gathering abilities in t-stops instead of f-stops. The difference is an f-stop (i.e. f/2.8) is a theoretical value of how much light can be gathered. Actually, it’s a ratio of aperture size to focal length. Most in the industry look at the f-stop and determine that as the measurement of light a lens is capable of capturing. The smaller the f-stop, the more light can be gathered. The reality is that not all lenses are created equal. Some factors can limit the amount of light going through the lens, despite a wide aperture. In the video/film industry, different cameras on a scene need to match exposure and white balance to be the most efficient and consistent visually. As a result, the light cine lenses can capture are measured in t-stops, which are actual lab tested measurements of light that can be gathered. The same principle applies that the lower the t-stop, the more light can be captured. However, since these are tested measurements, cinematographers know they can match exposure between cameras accurately. It can be expensive and time consuming for companies to measure a lens’ t-stop, which factors into the added cost of a cine lens.

Wrapping up

Cine lenses are designed for the video industry, but most of their benefits are easy to miss. They can be used for photography as well, though they’re not designed to. They may be sharper than a photography lens, but this can also depend on the lens. Ultimately, they offer smooth focusing and exposure transitions along with precise controls for the cinematographer to capture the right image. Is the added price justified? Perhaps not to most people but when things like matching exposure and a guarantee of no focus breathing are important to a production, expect to pay a little more. 

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