Zoom in on Zoom Lenses – The How and Why
By: The Cooke Team | 3 min read
An introduction to cine zoom lenses
The Zoom Lens – the lens that afforded filmmakers new techniques, the lens that revolutionised news gathering, the lens that can be just as good as a prime? Perhaps… let’s deep dive into the history of the zoom and how it has developed over the decades.
If you consult the trusted American Cinematographer Manual then ‘by definition a PROFESSIONAL zoom lens is a precision optical/mechanical system, which can change its field of view without noticeably changing its aperture or focus.’ In physical design this is made possible by the use of complex cams and followers which control precisely designed and manufactured optical components.
Zoom lenses are frequently more intricate in their design, as well as physically bulkier and weightier compared to prime lenses. The intricacy of their optics makes it challenging to produce a zoom lens without some compromise in image quality. Traditionally, it was commonly believed that zoom lenses fell short optically when compared to prime lenses. This was largely due to varying image aberrations across the zoom range.
However, in the realm of modern zoom lenses from reliable manufactures this is no longer the scenario. A well-crafted contemporary zoom lens such as the Cooke Varotal/i FF can match the performance of a prime lens. There will however be added size and weight. This is primarily attributed to factors such as the higher count of optical elements and more complex design considerations to achieve similar precision and aberration correction as an equivalent prime lens.
This being said, the gains from utilizing zoom lenses abound – you’re not limited to the set focal lengths of your prime lens set – if you’re in a location where the shooting space prohibits ideal camera placement then a zoom lens can get you much closer to the most suitable framing than a prime set could. If working on a remote head or crane there’s more options for flexibility without having to loose time changing lenses. Then there’s the creative possibilities; adding speed to action through zooming in, revealing the vastness of a space a character is inhabiting through zooming out. Giving the camera a “roaming” style perspective reminiscent of newsreel footage or even the ever popular Dolly Zoom effect. The increase in quality over the years has also led to the real possibility of using a zoom as a “variable prime” without compromise of clarity.
Cinema zoom lenses became popular in the 1960s and 70s. To begin with, zooming within a shot was frequently employed and some may feel it was overused which lead to a dated reputation. But like any technology, if used to support the story and emotions it can be an incredibly useful tool.
The range of a zoom can be very short while others may have a significantly longer range. A matched set of zooms ideally gives you a crossover between ranges for increased flexibility and usability. Zoom ranges can be noted by the specific range (such as 30-95mm) or by a ratio (such as 10:1) or a multiplier (10x), the longest focal length in both these cases being 10-times longer than the widest.
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