What Makes Anamorphic Lenses Different?

INTRODUCTION

Choosing a set of lenses is one of those tools in a cinematographers toolbox that can influence how stories are visually presented and how they are practically shot. 

Anamorphic glass is different to normal spherical lenses in many ways, so much so that shooting anamorphic is considered a different format altogether.

But what is it that makes these lenses different? Let’s do a bit of a deep dive.

WHAT ARE ANAMORPHIC LENSES?

When light passes through an ordinary lens, it captures an image which is correctly proportioned and can be used straight away. Anamorphic lenses are a bit funky. Because of their differently shaped, oval, cylindrical glass elements, when light hits them it gets squeezed and produces an image which is compressed. 

Kind of like how fairground mirrors can squeeze reflections to make you look long and lanky.

This contorted format was invented for two reasons: to create a widescreen aspect ratio, while at the same time maximising the quality or detail in the image. To understand how this works we must quickly dive into the origins of how old 35mm film cameras worked.

35mm film runs vertically through a camera, which captures the full width of the negative at a height of four of these little perforations tall. This is all well and good when shooting in the old, tall academy aspect ratio, but what if you wanted to film and present images in a widescreen format?

Well, you could take that taller frame and chop off the top and bottom with a mask. But that meant that when capturing or projecting you would waste a lot of expensive film that would just be blacked out and because the full height of the negative was cropped, the recording area was smaller, which decreased the clarity and quality of the recording and increased the amount of film grain you’d see.

SQUEEZE FACTOR

Anamorphic lenses fixed this by recording the full height and width of each four-perf frame, by squeezing the image to cover the entire negative. When screening the film in a cinema they then attached an extra anamorphic lens onto the projector which desqueezed the image - reverting it back to its correct proportions by stretching it out by the same amount that the anamorphic lens originally squeezed it.

The amount that the lenses compressed the image is called the squeeze factor. This refers to the ratio of horizontal to vertical information captured by an anamorphic lens. So regular spherical lenses that capture normal looking images have a factor of 1x, where the horizontal and vertical information is the same. While anamorphic lenses usually have a squeeze factor of 2x. This means that twice as much horizontal information is squeezed into the image than vertical information.

Although a 2x factor is the norm for anamorphic glass, there are also some lenses with different squeeze factors out there - which we’ll get to a bit later.

DESQUEEZE

Now that all post production, and almost all cinema projection, happens digitally rather than with film - the method for desqueezing footage has also changed.

You can now import files shot with anamorphic lenses into editing software, and apply settings to desqueeze the footage digitally, for example by a factor of two, to make the images uncompressed in a native widescreen aspect ratio.

ASPECT RATIO

Although the exact aspect ratio, or width, for anamorphic capture and projection may change ever so slightly depending on a few factors, it will usually either be 2.35:1 or, nowadays, 2.39:1 - which is more commonly referred to in more general terms by rounding it up and calling it a 2.40:1 aspect ratio.     

SUPER 35

Before I mentioned that an alternative method to get to this widescreen aspect ratio is by shooting with spherical lenses with a 1x factor, and cropping off the top and bottom of the frame.

Although this method yields less surface recording area and slightly diminished quality and resolution of detail, it is still a very commonly used format over anamorphic for a number of reasons.

Because widescreen Super 35 records extra information on the top and bottom of the frame, this can be useful in post for things like CGI, stabilising the image with software, or cropping out unwanted things by reframing up or down.

SPHERICAL VS ANAMORPHIC CHARACTERISTICS

Spherical lenses are also usually sharper across the width of the frame, meaning that details on the edges of the shot that are in focus will remain sharp. Anamorphic lenses have a sweet spot in the middle of the frame that will be sharp when in focus, while the edges of the frame will resolve detail less sharply. 

Another difference between spherical and anamorphic lenses is how their bokeh is rendered, which is the out of focus area in an image. Because the glass elements in 1x spherical lenses are rounded they produce rounded balls of bokeh.

However, anamorphic lenses, with their cylindrical elements that squeeze the image, create bokeh which takes on more of an oval shape. This shape is also affected by where the cylindrical glass element is placed within the lens. 

Most true anamorphic lenses place the cylindrical element at the front of the lens, with regular circular elements behind it. These are called front anamorphics and produce that classic ovular distortion in the background.

There are also rear anamorphic lenses, which instead place the cylindrical element at the back of the lens, with the rest of the circular elements in front of it. This is often done to create Frankenstein anamorphised zooms, which takes an existing spherical zoom lens and adds a rear anamorphic element to the back of it. 

This has the same effect of squeezing the image, however rear anamorphics often lose the oval bokeh shape, which becomes a bit more rounded or even, in some cases, rectangular.

Probably the most defining characteristic of anamorphics is their flare. When direct, hard light enters these lenses it produces a horizontal flare across the width of the image - which is usually quite pronounced.

Spherical flares tend to generally be a bit tamer and subtler and flare in a more circular way, rather than horizontally.

ANAMORPHIC IN A DIGITAL WORLD

Many digital cinema cameras use a sensor that approximately modelled the size of a Super 35 negative with a 4:3 ratio. This meant that most existing anamorphic lenses which were designed for four-perf film would be able to cover the width of digital sensors without vignetting.

Like on film, these 2x anamorphic lenses could cover the full height and most of the width of the sensor, filling a greater overall surface area than shooting a cropped Super 35 image with spherical lenses.

However, not all digital sensors used such a tall 4:3 ratio. Some sensors were designed to be more of a 16:9 size. There are some anamorphic lenses with a different 1.3x squeeze factor, instead of the standard 2x squeeze, that cover these wider sensors and still produce a widescreen image with a 2.40 aspect ratio.     

In recent years, full frame and large format digital cameras have seen a surge in popularity. Due to these sensors being significantly larger than Super 35, most 2x anamorphic lenses don’t have glass elements wide enough to cover these sensors without them seeing inside the lens and the image vignetting.

Anamorphic lenses with various squeeze factors have been designed to cover these format sizes, from 1.3x to 1.8x.

LIMITATIONS

A limitation of shooting large format or full frame anamorphic lenses is that you have a smaller selection to choose from and this glass is typically more expensive than comparable spherical options.

Spherical primes sets also usually come with far more focal lengths to choose from. For example a modern set of spherical primes like the Master Primes come in 16 focal lengths, whereas a modern set of anamorphic primes like the G-Series come in eight focal lengths. 

This sometimes means that cinematographers like to pair a set of anamorphic primes with a longer zoom - which may either be an anamorphised rear zoom, like we mentioned before, or a front anamorphic zoom like the Panavision 70-200mm.

Another potential limitation of anamorphics, especially front anamorphic zooms, are that because of their more difficult design and increased number of glass elements, they usually have a slower stop than their spherical peers - which renders a tad less bokeh and makes it more difficult to shoot in very low light conditions.

They are also on average physically larger and heavier than spherical lenses - with the gigantic Primos being a great example of just how hefty a prime anamorphic lens can get. Although many lighter alternatives do also exist.

Close focus can also be an issue. The extra glass in anamorphic lenses means that the MOD, or the closest point that the lens can render an object in sharp focus, is usually not very near. 1x spherical glass is normally far better at this. So, if filmmakers want to shoot an extreme close up on an anamorphic lens, they will need to use an extra diopter filter which allows them to achieve more of a macro focus.

Visually, anamorphics produce more distortion, with the wider focal lengths, around 40mm and wider, bending the edges of the frame - which is especially noticeable when shooting something with a straight line like a door frame. 

WHY CHOOSE ANAMORPHIC LENSES?

So, broadly, spherical lenses offer a greater practical flexibility to cinematographers, while anamorphic lenses offer a specific look, in exchange for a few practical tradeoffs.

Overall, DPs who like a clean look to their footage, which is sharp across the frame and free of aberrations or distortion often like to go with spherical glass and crop to get a wide aspect ratio. Whereas those looking to add a touch more visual character to the footage to make it a little less perfect, which is often done to counteract the sharpness of modern high res digital cameras, may prefer the look of older anamorphic lenses.

Having said that, there are exceptions to this. Old, vintage spherical lenses exist which offer a lot of imperfections, as well as modern anamorphic lenses which are very sharp and clean. 

In the end, anamorphic lenses can give projects a look that has long been considered classically cinematic, with their oval bokeh, lateral flares, falloff and native widescreen ratio. However, this does come with a few practical tradeoffs which may need to be considered by filmmakers.