Anamorphic - Guillermo Algora - Visual Effects Compositor

1. Format

2. Visual Properties:

2.1 Depth of field:

2.1.1 Bokeh.

2.1.2 Focus Breathing.

2.2 Lens Sharpness.

2.3 Chromatic aberration.

2.4 Flares.

2.5 Vignette.

2.6 Lens Distortion.

2.7 Grain.

Anamorphic format is all about capturing a wider image on film or digital sensors without actually changing the sensor size itself. These specialised lenses have an extra element inside them that essentially squeezes the image horizontally as it's captured on the film or sensor. Imagine a wide scene you want to capture. A standard lens would cut off some of the sides to fit it on the frame. An anamorphic lens squeezes it all in, like a panoramic photo, but keeps the vertical height the same. During projection or post-processing for digital cameras, the image is then stretched back out horizontally to its natural wide aspect ratio, typically around 2.39:1 (often called 2.4:1). This creates that expansive cinematic view. It's the industry standard for theatrical releases.

Squeeze:

There can be some variation in squeeze factors, but here are the most common types of anamorphic formats based on their squeeze factor:

2x squeeze: This is the classic anamorphic format, originally designed for 35mm film. It squeezes the image horizontally by a factor of 2 and achieves the 2.39:1 aspect ratio when projected or de-squeezed in post-production.

1.33x squeeze: This squeeze factor is becoming increasingly popular, especially for digital cameras with wider sensors than traditional 35mm film. It creates a more moderate wide-screen look compared to the 2x squeeze, sometimes referred to as "mild anamorphic" and often achieving an aspect ratio around 1.85:1.

Other squeeze factors: Less common are even wider squeeze factors like 1.55x, which can create a very expansive look but might require additional cropping in post to achieve a usable aspect ratio.

PAR:

This footage is then unsqueezed during post-production to achieve a widescreen aspect ratio. The result is that anamorphic footage often has non-square pixels, meaning the Pixel Aspect Ratio (PAR) is not 1:1.

Set the Correct PAR: Determine the PAR of your anamorphic footage. This is usually specified by the camera or lens documentation. In the Read node, set the Pixel Aspect Ratio to match the PAR of your footage. For example, if your footage has a PAR of 2:1, set the Pixel Aspect Ratio to 2.

2.1 Depth of Field:

Bokeh:

• Oval Bokeh: The most distinct characteristic of anamorphic bokeh is its shape. Instead of circular blur points like regular lenses, anamorphic lenses create oval or elliptical bokeh shapes, especially for out-of-focus highlights.

• Smooth and Pleasing:  Anamorphic bokeh is often described as smoother and more aesthetically pleasing compared to regular lenses. This contributes to the distinctive "cinematic" look associated with anamorphic footage. Regular lenses create bokeh with a harsher transition between the in-focus area and the blurred background. Anamorphic lenses, due to their design, create a smoother gradient between the two. Imagine a circle (regular bokeh) transitioning abruptly into blur compared to a stretched oval (anamorphic bokeh) with a gentler transition. The oval shape itself is often found more aesthetically pleasing. Circles can appear a bit busy or distracting, whereas the elongated oval tends to blend more seamlessly with the background.

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. This anisotropic bokeh contributes to the unique aesthetic of anamorphic cinematography. Bokeh circles in regular footage are generally isotropic, meaning they have a uniform shape and size regardless of their orientation relative to the frame.

• Bokeh circles may be more densely packed or clustered in certain areas of the frame, particularly towards the edges or corners, due to the optical properties of anamorphic lenses.

Focus Breathing:

• The wider the aperture, the more obvious the breathing is with anamorphic lenses. Anamorphic breathing is a little different than normal spherical lens breathing where the image appears to change focal length as you rack focus. With anamorphic lenses, the amount of vertical stretching of the bokeh changes as the focus changes, so focus racks become more noticeable. As you rack focus from far to near, for example, the background gets skinnier-looking. Since stopping down the lens reduces the amount of out of focus bokeh shapes, this type of breathing is less obvious when you have more depth of field. If you shoot with an anamorphic lens at f/11, for example, there is less visible vertical stretching in the background as you rack focus. Of course, anamorphic lenses also have some breathing issues like spherical lenses where the focal length appears to change. But that is less distinctive than the vertically stretched bokeh look. It’s common to call the stretching and squashing of the background as you rack focus in anamorphic “breathing” — in fact, I’ve never heard of an alternative term for the artifact.
• But there's a difference between the background field of view stretching or squishing because of a focus rack and the Bokeh stretching or squishing as a point source defocusses. Otherwise we could equally call an expanding out-of-focus highlight caused by a focus pull in spherical cinematography breathing, even if there was no actual change in the field of view occurring.
• Im just saying that when most people refer to anamorphic lens breathing, like in the original post, they arent talking about regular spherical lens breathing... if they were, there would be no point in specifically mentioning anamorphic lenses.
• When you shoot with anamorphic lenses, the effect when you rack focus is as distracting as when a spherical lens breathes badly, enough to make you minimize how often you rack focus during a scene. And the effect is similar to regular breathing in that there is a change to the image during the rack, its just that rather than a slight zoom in and out, its a vertical stretch that comes and goes. The only difference compared to spherical lens breathing is that the effect is minimized the more you stop down because less of the image is out of focus. I brought this up originally because the poster wanted to maximize the effect.
• Well we might have to disagree that anamorphic breathing is a different thing to spherical breathing. The change in image magnification can be more pronounced in one axis with anamorphic, rather than uniform, but it's the same phenomenon, caused by lens elements shifting position relative to one another.
• If you look at the posted tests of Lomos and Hawks above, you can see very noticeable horizontal breathing, much more distracting than any sense of vertical stretching caused by the Bokeh. From your description I suspect your experience is mainly with Panavision anamorphics, which breathe mainly in the vertical axis. However that "stretch" (or change in vertical field of view) will occur to the same degree regardless of aperture, the effect is not minimised by stopping down. The Bokeh and the breathing are two seperate things, but in the case of Panavision I can see how the vertically expanding individual elements of the Bokeh might seem part of the same effect, and draw more attention to the breathing. Stopping down a spherical lens also makes a focus pull less obvious, since there is less change in the Bokeh, but that's also unrelated to breathing.
• Dom, I think you're technically correct and that I am conflating two separate issues which is the amount of distortion (breathing) that happens with anamorphic lenses to the background when you focus from far to near (the fact that anamorphic lenses start to compress more than 2X in the out of focus areas) and how visible that change is due to depth of field. The distortion doesn't change with f-stop but your eye notices it more when the image is very shallow in focus because of the way that the background is reduced to abstract shapes. So basically not what the other says.