With interchangeable lens cinema cameras forever dropping in price and availability, the market for lenses designed for cine and video applications is more popular than ever before. But what are the differences between cine lenses and photo (still) lenses, and what factors should you consider when picking up your first cine lens?
Our new video, which was created as part of ‘Canon in Motion’, highlights the key differences and the best ways to deal with the changes, which we have summarised below.
Mechanical Build
The intended use and application of a lens will shape the way its mechanics are designed and is probably where the biggest differences between cine and photo lenses lie.
Unlike the multi-use nature of a photo lens, cine lenses are designed specifically for moving images and can involve a completely different workflow and shooting style that often include dedicated crews and operators. Things like size, build quality and surrounding accessories are also considered differently and is why using photo lenses for cinema and video production can be full of compromises.
Cine lenses are designed with consistency and control in mind. Consistency of size makes lens swapping easier when using support and motion control equipment, and consistent gear ring placement means less time moving motors around. It also makes balancing your rig or stabilisation equipment much faster.
The use of filtration is relatively easy with stills glass, with the most common method being threaded filters that screw on directly to the front of your lens. The downside of this method is that photo lenses are very inconsistent with their thread diameter, meaning you might have to buy multiple filters in different sizes or use an accessory such as the Revoring, which is essentially a variable step up ring. While some cine lenses do feature threads for screw-on filters, the most common way of adding filtration to this type of lens is with the use of a matte box system. Attaching a matte box can be done with either a rod support system, which can work more universally across most lenses, or by using a clamp-on system that is designed to attach a matte box to the front of your lens.
Mounts
The PL, or Positive Lock mount was introduced by ARRI in the 1980’s and is the most used lens mount in the mid-to-high-end cine market, being recognised as a standard by most lens and camera manufacturers.
Compared to the mounts found on photo lenses, the PL mount is a much more secure system with a locking design that greatly reduces any play in the mount that could translate to image shift while focusing or zooming.
With full metal bodies and often with larger lens elements, these heavier cine lenses have a need for greater mount stability, and can also benefit from the use of a lens support for further elimination of image shifting and additional support and safety.
Many cinema lenses feature an Interchangeable Mount, allowing a changeover from one mount to another, such as from PL to EF. The added flexibility that an Interchangeable Mount brings means it’s an attractive option not only for end users who want to use their lenses across multiple camera systems, but also to rental houses who don’t want to limit their lenses to one mount, adding versatility and renting potential to their investment.
It can be challenging to change mounts properly if it’s something you are new to or lack the correct tools needed. A selection of Canon’s cine lenses can only have their mounts changed by a Canon approved service centre – they are not designed to be changed by the user.
Aperture
As previously mentioned, cine lenses are designed for consistency and control, and this can be illustrated best by the way aperture is handled on a cine lens compared to a photo lens.
Anyone working with stills lenses will be familiar with F-Numbers or F-Stops. F-Stop is a mathematical value that is calculated by dividing the lens’ focal length by the diameter of the entrance pupil to get a theoretical value of light hitting your sensor. By contrast, cine lenses use T-Stops, which is an actual measured amount of transmitted light being received by the sensor through the lens. This standard is used across all cine lenses with an aim to keep consistent exposure across multiple lenses at the same T-Stop values, helping to match exposure precisely when using multiple cameras. This would also mean that you could switch to a different focal length of the same T-Stop value while shooting a scene, whilst maintaining the same exposure. This is more applicable for lenses within the same set, as each manufacturer rates their T-Stop values individually.
When it comes to adjusting your aperture, the different mechanics between photo and cine lenses offer different levels of control when setting your F or T Stop. With most photo lenses, aperture is controlled through the camera with electronic adjustments being made in discrete steps. While this method can be quick and easy for a single operator, it limits how precise you can be and the stepped adjustments can be noticeable both visually and audibly if done when recording. Manual control of a cine lens allows for continuous adjustments of the iris without any hard steps. This means exposure changes can be made smoothly while recording and, with a nice long rotation distance, you have much more precision over your aperture.
Focus
One of the biggest differences between cine lenses and photo lenses is focusing, both in terms of mechanics and characteristics. Photo lenses are most often electronically driven with quick and accurate autofocus being an important feature; conversely, the manual mechanical focus of a cine lens is designed for precise, human operation. However, there are a few hybrid cinema lenses which feature electronic capabilities, such as Canon’s Cine Servo lenses which feature the ability for zoom focus and iris to be controlled electronically, with some even having autofocus capabilities.
A lens’ focus throw is the measurement of the focus ring’s rotation from close focus to infinity in degrees. Cine lenses typically have a much longer focus throw for smoother, more precise adjustments, with extra room on the focus ring for better spacing of markings (which is really important to someone using these marks to pull focus). These marks can be in either metric or imperial – make sure your lens has the markings relevant to your region. The focus ring on cine lenses tend to have a hard stop at either end of the focus range, whereas most photo lenses will continue to rotate beyond close focus or infinity. Not having this hard stop means your focus ring position is not directly attached to the focus scale, and any added marks on your lens or follow focus could be lost.
Breathing is a term used to describe the slight focal length change that can happen when moving through a lens’ focus range. It’s a characteristic that is common in photo lenses as it is something that will not be noticed when capturing a single frame.
With moving images however, it can be seen as distracting, so most cine lenses are optically designed to minimise focus breathing. That being said, like many optical imperfections, this may in fact be a desired effect in some situations.
Another optical trait that cine lenses outperform in is parfocality. A parfocal lens is a zoom lens that can maintain its focus while having its focal length changed – an important feature to many video shooters. Parfocality is less of a concern with photo lenses due to the use of autofocus. Engineering a zoom lens to be parfocal is incredibly challenging and is something that is later reflected in its price tag. Another advantage with cine zooms is that, more often than not, all the moving parts relating to zooming are kept internal, whereas a lot of photo lenses tend to trombone as you zoom. Internal zooming and focusing means you will spend less time adjusting accessories such as a matte box or motors and will also help keep your rig balance more consistent.
It’s important to note that having your cine lenses properly calibrated is more important than with photo lenses. Not having your lens calibrated correctly could result in issues such as focus scales being out or zooms not being parfocal. Our in-house ProRepairs team has a specialised lens department that can service your lenses, making sure they are within manufacturer specification and accurate for you.
Stabilisation
Optical stabilisation is a technology that predominantly features in photo lenses, with use for both photography and video work, but has never made its way over to cine lenses.
There are a few reasons for this – one being that mid-to-high-end cine lenses are designed with a certain assumption that they will be used in shooting scenarios with other camera stabilisation or support equipment. The lack of optical stabilisation allows for the lens’ design to be better focused (no pun intended) on performance, and having fewer moving parts also increases reliability on set. Some hybrid lenses, such as the Canon CN-E Servo Zoom, do feature in-lens stabilisation because they are aimed at more of a ‘run and gun’ documentary market compared to their larger cine zooms and primes. Without optical stabilisation, the easiest way to steady your movements while shooting handheld is to add weight to your camera rig; otherwise you may need to invest in other stabilisation equipment such as a Steadicam, gimbal, slider or just a trusty pair of sticks.
Image Quality
Image quality differences between cine and photo lenses can usually be quite obvious, although this isn’t always the case.
There are differences in the level of quality control when it comes to both the optical elements and the overall look of lenses across an entire set. More often than not, you are buying cine lenses as a partial or complete set, unlike with stills glass which are rarely sold as sets.
The consistency of how lenses look across a set is very important for productions that want to keep the look of their image the same across a large range of focal lengths. This relates to everything that we look at when evaluating image quality.
Canon has done a good job of making their lenses decently consistent across their sets, and even their cine zooms match pretty well with their CN-E primes.
Pricing
Factors like better consistency contribute to cine lenses higher price tag vs photo lenses. Additional differences like higher QC’ing tolerances, higher variety and quality of manufacturing materials, longer design and production times, and being part of a smaller market, are all reasons why cine lenses are typically valued much higher to a stills equivalent.
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Need more information?
Lens choice can be incredibly subjective based on characteristics and quality; however, a lens’ mechanics are a little more objective with different productions and filmmakers requiring different feature sets.
For more tailored advice on lenses and their surrounding accessories, contact the CVP team with your requirements or get in touch via the live chat and we’ll get back to you shortly.
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