ANAMORPHIC
Anamorphic lenses are a special type of lens used to achieve a widescreen format while maximising image quality. These lenses compress the incoming image horizontally onto the camera's sensor or film plane, allowing a wider field of view to be captured while maintaining the full height. During projection/post-processing, the image is stretched back horizontally. Due to the horizontal squeeze during image capture, the image presents some distinct visual properties, often used creatively. At the same time, by capturing a much wider scene than a standard lens, it offers a more immersive visual experience.
1. Format:
Anamorphic format is all about capturing a wider horizontal image, while preserving the vertical information, without actually changing the film or digital sensor size. These specialised lenses have an additional element inside them that essentially squeezes the horizontal field of view upon a squeeze factor (typically 2x, 1.8x, 1.33x...) allowing for more information to be captured along the horizontal axis. During projection or post-processing, the captured image is restored (stretched back horizontally) to its natural wide aspect ratio, for example the 2.39:1 (often called 2.4:1) format, which is the traditional industry standard for theatrical releases that produces an expansive cinematic view.
1.1. Squeeze Factor:The squeeze factor is defined by the lens itself, which is often chosen purposely in order to accommodate once unsqueezed the desired final aspect ratio in relation to the film/sensor format, while at the same time considering its visual rendering characteristics (e.g. higher squeeze factors create a stronger anamorphic look). Although there are multiple squeeze factors, these are some of the most common:
- 2x: It squeezes the image horizontally by a factor of 2. This is the classic anamorphic format, originally designed for 35mm film (which has a native aspect ratio of 1.33:1), and when paired, the horizontal width doubles leading to after a slight trimming of the vertical axis a 2.39:1 final aspect ratio.
- 1.33x: This squeeze factor is becoming increasingly popular, especially for digital cameras with wider sensors than traditional 35mm film. On many modern digital sensors (with a native 16:9 or 1.78:1 aspect ratio) a 1.33x anamorphic lens is often used. The horizontal field of view is compressed by 1.33x, and when unsqueezed, the final aspect ratio becomes 2.39:1, matching the widescreen look without as much horizontal compression as a 2x lens.
- Other squeeze factors are the 1.75/8x, often used in digital cinema 4:3 full-frame sensors (open gate) leading to a close 2.39:1 when unsqueezed. Squeeze factors like 1.5x, when paired with a 16:9 sensor deliver a 2.66:1 aspect ratio, slightly wider than the 2.39:1, which can therefore create a very expansive and characteristic look (similar to a 2x factor on a 4:3 sensor).
1.2. Pixel Aspect Ratio (PAR):Pixel Aspect Ratio is the ratio of the horizontal to the vertical pixel size. When working with anamorphic footage, the images are captured with a horizontal squeeze but stored using square pixels (1:1 PAR) in the digital file. During playback or post-processing, the footage is unsqueezed to achieve the widescreen aspect ratio. This unsqueezing process doesn't actually change the pixels themselves, but rather instructs the display or software to interpret them with a non-square PAR. For example, with a 2x squeeze factor, the display system treats each pixel as if it were twice as wide as it is tall (2:1 PAR), effectively stretching the image horizontally without actually changing the stored pixel data.
Different Anamorphic Formats
Squeezed (2x factor) vs Unsqueezed (2.39:1 format)
Recorded in sensor (original) vs Post-processing (display)
PAR 1:1 (original) vs PAR 2:1 (display)
2. Visual Properties:
2.1. Depth of Field:
- Shallower: while spherical and anamorphic lenses yield the same depth of field, to produce the same angle of view in anamorphic a longer focal length is employed, which means that at the same magnification there is generally shallower depth of field. In addition, the way that anamorphic lens squishes the background also enhances this effect, making the blur look stronger.
2.1.1. Bokeh:
Oval:
The most distinct characteristic of anamorphic bokeh is the shape. Instead of "circular" or symmetrical blur points like regular lenses, anamorphic lenses create oval or elliptical bokeh shapes, especially for out-of-focus highlights. This is due to the asymmetrical focal lengths between the horizontal and vertical planes, which leads to an asymmetrical depth of field for out-of-focus elements (longer focal length in the vertical plane, shallower depth of field), causing them to blur more in the vertical direction than in the horizontal direction , resulting in a vertically oriented oval bokeh.Anisotropy:
Anamorphic lenses can introduce anisotropic bokeh, where the shape and size of bokeh circles vary depending on their orientation relative to the horizontal and vertical axes of the frame, resulting in longer and more pronounced oval shapes towards the edges. This is due to the cylindrical elements that compress the image horizontally, introducing optical aberrations that become more pronounced away from the optical center. At the edges and corners, light rays travel through the cylindrical elements at more extreme angles, causing greater differential magnification between the horizontal and vertical axes, resulting in more exaggerated oval-shaped bokeh at the edges compared to the center. The subtle rotation of bokeh elements toward the edges is influenced by a phenomenon called "pupil aberration" or "pupil geometry distortion," along with field curvature and astigmatism. In anamorphic lenses, the entrance pupil (the apparent aperture as seen from in front of the lens) becomes asymmetrically distorted toward the edges, creating a slight rotational effect on out-of-focus highlights. Light rays entering from off-axis points experience this asymmetrical pupil shape combined with differential magnification, causing the bokeh to exhibit a subtle rotation that becomes more pronounced farther from the center.This is distinct from the cat's eye effect in spherical lenses, which is primarily caused by mechanical vignetting (the physical aperture being partially obscured when viewed from off-axis angles). While spherical lenses show symmetrical cat's eye shapes pointing toward the center, anamorphic lenses exhibit a more complex combination of stretching and subtle rotation that varies across the frame. The effect in spherical lenses is more symmetrical and predictable across the frame, where bokeh at equal distances from the center generally shows similar shapes. Spherical lenses typically do not exhibit the same degree of bokeh rotation as anamorphic lenses, as their ellipses remain oriented toward the center. The distortion is generally less pronounced than in anamorphic lenses, particularly in modern high-quality spherical optics.The anisotropic bokeh significantly contributes to the unique aesthetic of anamorphic cinematography.
2.1.2. Focus Breathing:The key characteristic of anamorphic breathing is that the horizontal and vertical magnification changes at different rates during focus shifts, which results in an asymmetrical expansion or contraction of the image. Although anamorphic breathing can also exhibit some degree of spherical lens breathing (i.e. a more symmetrical change in the lens's focal length, resulting in an apparent zoom effect where the entire image subtly enlarge or shrink as the focus distance is adjusted), this is often overshadowed by the more visually distinctive asymmetrical distortion. This unique breathing in anamorphic lenses stems from the interaction of the cylindrical and the spherical elements, which react differently during focus shifts, and therefore the horizontal and vertical dimensions changing at different rates.The direction and magnitude of focus breathing in anamorphic lenses are intrinsic characteristics dictated by their specific optical design and can vary considerably across different lens manufacturers and their respective models. For example, some designs my present an stronger visual distortion on the vertical or otherwise on the horizontal axis.
2.2. Lens Sharpness:
May generally exhibit lower overall sharpness than comparable spherical lenses, due to:
- The additional internal elements to achieve the wider horizontal field of view, which may introduce additional and non-uniform aberrations, while a wider field of view creates more extreme angles for light to pass through the lens, which leads to increased difficulty maintaining consistent sharpness from center to edge.
- The focus fall-off toward the edges in anamorphic lenses is more pronounced and asymmetrical. This is because anamorphic lenses focus light differently in horizontal vs. vertical planes, intentionally introducing astigmatism (where horizontal and vertical lines focus at different distances) to create the squeeze effect. The interaction between cylindrical and spherical elements creates varying focal points across the frame. In optical engineering, every lens is evaluated for how it focuses light in sagittal (radial) and tangential (perpendicular to radial) directions. In spherical lenses, these two focus planes are close together. In anamorphic lenses, these planes are significantly separated by design, creating an undulating effect (link). For anamorphic lenses, these maps show complex undulations rather than simple curves. Spherical lenses tend to have more radially symmetrical aberrations - any curvature tends to be uniform around the optical axis, and typically show a single curved focus field (usually either inward or outward), not multiple undulations. This test would reveal a much more complex pattern with anamorphic lenses than with spherical lenses, where focus typically falls off in a more uniform pattern from center to edge.
2.3. Chromatic Aberration:
In anamorphic lenses, chromatic aberration is often more severe than in comparable spherical lenses. The cylindrical elements used to create the horizontal compression, disperse different wavelengths of light at different rates along the horizontal and vertical axes, leading to asymmetrical chromatic aberration patterns are usually more pronounced in the horizontal dimension. In addition, the complex optical design with additional glass elements creates more opportunities for light dispersion.
Lateral chromatic aberration (which occurs toward the edges of the frame) is especially visible in anamorphic systems. Near the frame edges, there is often more pronounced color fringing, typically appearing as blue/purple fringing on one side of high-contrast edges and yellow/green fringing on the opposite side. This effect intensifies with older or less corrected anamorphic designs.
2.4 Flares:
- The key difference in lens flare between anamorphic and regular (spherical) lenses comes down to the shape they produce. The cylindrical element scatters and refracts asymmetrically, creating elongated horizontal streaks rather than the more circular or star-shaped flares typical of spherical lenses.
- Most traditional anamorphic lenses produce flares with a distinct blue or blue-cyan tint. This color bias occurs because the coatings used on the cylindrical elements tend to reflect and scatter blue wavelengths more prominently than other colors. In vintage anamorphic lenses, this effect was often more pronounced due to the simpler lens coatings available at the time. The blue tint has become so associated with the anamorphic look that even modern lenses often deliberately preserve this characteristic.
- Anamorphic flares typically exhibit several unique properties:
- Horizontal orientation regardless of camera position or movement.
- Strong blue-cyan color cast, mostly applicable to vintage designs, as modern anamorphic lenses often offer a wider variety.
- Often greater length and prominence than spherical lens flares.
- Ability to stretch across the entire frame when a bright light source is just outside the frame.
- Distinct internal structure with lines and streaks.
2.5. Vignette:
Anamorphic lenses typically exhibit more pronounced vignetting, particularly along the horizontal edges of the frame, creating an asymmetrical light fall-off pattern that adds to their distinctive visual signature. The cylindrical elements that create the horizontal compression inherently restrict light transmission toward the edges of the frame. This occurs because light must travel through more glass at oblique angles to reach the sensor or film plane at the frame edges. Since anamorphic lenses compress the horizontal field of view, the vignetting effect is often more pronounced along the sides rather than the top and bottom of the frame, creating an oval or elliptical vignetting pattern rather than the more uniform circular pattern typical of spherical lenses.
Interestingly, the interaction between vignetting and the oval bokeh characteristic of anamorphic lenses creates a distinctive depth effect where out-of-focus areas toward the frame edges appear to recede more dramatically than with spherical lenses. This contributes to the three-dimensional quality that cinematographers often seek when choosing anamorphic lenses.
2.6. Lens Distortion:
Unlike spherical lenses that generally tend to show more uniform distortion patterns, anamorphic distortion is inherently asymmetrical, affecting horizontal and vertical lines differently.
- The most notable distortion in anamorphic lenses is the "anamorphic mumps". This distortion occurs because the squeeze factor of the lens doesn't remain perfectly consistent across all focusing distances, often decreasing slightly at minimum focus distance compared to its value at infinity, causing the horizontal dimension to stretch relative to the vertical. This effect causes objects to appear slightly stretched horizontally when the focus shifts to a closer distance (proportionally wider compared to how they look at further focus distances).
- Anamorphic lenses also typically exhibit a unique form of geometric distortion where straight lines, especially toward the edges of the frame, show different bending patterns horizontally versus vertically. Vertical lines near the frame edges often bow outward (barrel distortion), while horizontal lines may bow inward (pincushion distortion), remain relatively straight or even display complex wave-like (mustache) distortion, depending on the lens design. During camera movements, this complex and often asymmetrical distortion can create a dynamic effect where the geometry of the scene appears to subtly warp, contributing to the unique anamorphic look.
2.7. Grain:
Grain results stretched out horizontally by the squeeze factor during the projection or post-processing, creating a slightly elongated grain pattern.
2.7. Front vs Rear mounted:
The type of anamorphic lens can also be an important factor. Most of the characteristic look of anamorphic lenses is associated with the front-mounted type, where the aspect ratio compression is done by a front lens element, and the light already altered before passing through the spherical element.
In rear-mounted anamorphic lenses, the iconic anamorphic look will generally appear less pronounced, and are therefore typically used when utilizing more film/sensor area is the primary goal rather than the aesthetics. This is because the placement of the anamorphic element at the rear of the optical path means that the light has already been focused by the spherical lens before undergoing horizontal compression, leading to a less dramatic alteration compared to front anamorphic designs.
Rear-mounted anamorphic lenses often increase the effective focal length. A rear anamorphic adapter increases the effective focal length by approximately the same factor as its squeeze ratio, due to the increased flange distance (elements appear larger, in the amount of the squeeze ratio, than they would with just the primary lens). However, the increase in magnification effectively only ends up happening in the vertical dimension, as in the horizontal dimension the adapter compresses the image by its squeeze ratio, counteracting the magnification effect (the horizontal field of view remains close to what the primary lens would show without the adapter). The compression factor essentially cancels out the focal length increase in this dimension. Due to this combination of effects is why rear anamorphic adapters produce images with a distinct "telephoto feel" even though they maintain a wider horizontal field of view than a true telephoto lens would.
In rear-mounted anamorphic lenses, the iconic anamorphic look will generally appear less pronounced, and are therefore typically used when utilizing more film/sensor area is the primary goal rather than the aesthetics. This is because the placement of the anamorphic element at the rear of the optical path means that the light has already been focused by the spherical lens before undergoing horizontal compression, leading to a less dramatic alteration compared to front anamorphic designs.
Rear-mounted anamorphic lenses often increase the effective focal length. A rear anamorphic adapter increases the effective focal length by approximately the same factor as its squeeze ratio, due to the increased flange distance (elements appear larger, in the amount of the squeeze ratio, than they would with just the primary lens). However, the increase in magnification effectively only ends up happening in the vertical dimension, as in the horizontal dimension the adapter compresses the image by its squeeze ratio, counteracting the magnification effect (the horizontal field of view remains close to what the primary lens would show without the adapter). The compression factor essentially cancels out the focal length increase in this dimension. Due to this combination of effects is why rear anamorphic adapters produce images with a distinct "telephoto feel" even though they maintain a wider horizontal field of view than a true telephoto lens would.
This also comes along with an increase of the minimum focus distance, as the increased flange distance prevents the lens from focusing as closely as it normally would (the minimum focus distance often increases by approximately the same factor as the squeeze ratio). Rear anamorphic adapters also reduce the maximum available aperture, as they intercept the already-focused light cone, which inherently reduces light transmission. While front adapters allow light to pass through the full diameter of the primary lens, rear adapters interrupt the optimized light path, causing more significant light loss.
Vintage front anamorphic systems might usually employ dual-focus systems (requiring to focus the anamorphic and spherical elements independently) which also contributes to the anamorphic look, in comparison to the more common single-focus in rear mounted.