Why do anamorphic lenses look more cinematic?
The popularity of Anamorphic lenses is growing. They’re synonymous with a professional, emotional image and used in many high budget commercials and blockbusters. It is true that shooting in an anamorphic workflow can be more expensive than shooting in its counterpart, a spherical workflow. A set of Cooke anamorphic lenses can go for £900 per day. Because of this, the first thing new videographers ask themselves when first encountering anamorphic lenses are, what’s so special about the image? What will investing in an anamorphic workflow do to the image which a spherical workflow won’t do? Researching this question on the web doesn’t reveal much. Even an anamorphic video by Arri doesn’t say much more than anamorphic lenses produce over bokeh. In this blog, I’ll discuss all the facts about anamorphic lenses which aren’t often mentioned in YouTube videos and other blog posts. This is what is different about anamorphic lenses and why they create a more (what some would say) cinematic image than spherical ones.
Here’s some info about lenses which you can skip if you like. Basically, I’m going to explain how the depth of field becomes shallower as the focal length increases.
First, we have to address some basic science about spherical lenses. We are going to look at the relationship between focal length, f/stop and depth of field. It’s basic knowledge that a higher f/stop (wide aperture) create a shallower depth of field. If you didn’t know this, maybe this isn’t the blog post for you. Increasing the focal length also creates a shallower depth of field, the reason for this is as follows.
The f/stop is a dimensionless number but is used to work out the diameter of the aperture of the lens. To work out the actual diameter, we divide the focal length by the f/stop. Let's say we have a 50mm f.2 lens. =The diameter of the aperture would be,
50mm / f.2 = 25mm
The F in f/stop stands for focal length. By expressing f/stop in this way, with a ‘/‘, it’s basically telling us the sum we need to use to work out the diameter.
We can now address a different lens. A 100mm f/2. When the aperture is set to f/2, the diameter of the aperture would be
f/stop = 100mm/2 = 50mm
We can compare these two formulas were at f/2 on a 50mm lens, the aperture is 25mm and at f/2 on a 100mm, the aperture is 50mm. The f-number has stayed the same but as we increase the focal length, the aperture opening has widened creating a shallower depth of field.
I hope I’ve shown you here that, If the aperture is fixed, zooming in will shallow the depth of field because zooming in widens the aperture.
So the depth of field becomes shallower as the focal length increases. This is important when addressing anamorphic lenses because the unique thing about anamorphic lenses is that the focal length on the horizontal plane is different from the focal length on the vertical plane. For example, on a x2 anamorphic lens, where the vertical focal length would be 50mm, the horizontal length would be twice that at 100mm, therefore, a x2 lens. This is what creates the stretched image of anamorphic lenses. This image is then de-stretched afterwards in post to create a widescreen image. This is where many people get the facts wrong about the anamorphic image. The squeezing and de-squeezing do not create oval bokeh. As we stated earlier, a larger focal length creates a shallower depth of field. This is where the oval bokeh comes from. The fact that the focal length of an anamorphic lens is stretched and larger on the vertical plain means that the bokeh balls are larger on the vertical plain creating an oval shape. We can see this as the focus is racked on an anamorphic lens. Objects stretch as they fall out of focus because of the fact that the depth of field is shallower on the horizontal axes. This is one of the major differences between anamorphic and spherical lenses. There is no way to reproduce this phenomenon on a spherical lens and we only see this effect when using the anamorphic footage. Some people try to recreate the oval bokeh by putting oval-shaped cutouts in front of a spherical lens. This does not recreate the effect of anamorphic lenses, only the bokeh.
Photos of a £20 non-anamorphic lens being adapted to try and mimic the anamorphic bokeh and lens flare by sticking cut-out card to the lens. these then being sold for $159.
The squeezing and de-squeezing do affect some things. Barrel distortion is more common in anamorphic lenses and barrel distortion is heavier on the horizontal axes. Vignetting is also stretched horizontally too, unlike a spherical lens where it would be evenly throughout. The most obvious trait of anamorphic lenses is the lens flares which is created by the coating on the lens.
Zooming with an anamorphic lens is less common as they are very expensive. The director Egar Write like to zoom a lot but in his latest film, Baby Driver I remember thinking there is significantly less zooming (if any) than his usual stuff. Possibly because Baby Driver was filmed in anamorphic and the rest of his work usually isn't. You can see this when comparing a music video he filmed several years ago and one of the scenes from the film. Links are below.
Blue Song - Mint Royale - dir. Edgar Wright - https://www.youtube.com/watch?v=iHbndkcLM6A
Baby Driver scene - https://www.youtube.com/watch?v=qZhF7oRalp4
What we can take away from all this is that anamorphic lenses warp the image in many different ways. Most predominantly, the fall off of focus on the horizontal axes, unique lens flares and the elongating of lens aberrations such as vignetting and barrel distortion. What I would want to point out is, most of these don’t affect the subject at all. For example, a correctly focussed medium shot of a man framed in the centre would render an image of the man exactly the same as a spherical lens. It's all the other stuff in the peripheral which warp. Like the buildings of trees in the background warped and aberrations around the eyes of the lens warped like the vignette and barrel distortion. I believe this is why the lens flares are the most commonly known trait of anamorphic lenses as this is the only trait which can disrupt the line of view between the audience and the subject.
As many of the traits of anamorphic lenses are in the peripheral, this means they are much harder to notice to the untrained eye. What does happen is, the weird warping of the image sinks into the subconscious. For decades, much of the most cinematic films and high-end commercials have been shot on anamorphic, unknown to the untrained eye, but now, our subconscious has built a synonym between professional image and anamorphic lenses. This means that, when the general public sees a commercial or music video shot on anamorphic, the warping on the image makes it easier for them to feel that it’s of a professional quality. They wouldn’t be able to put their finger on why, but it’s very realistic it’s because of their subconscious association between the high-end image and the subtle traits of anamorphic lenses.
I now hope you understand where the oval bokeh comes to form, some more of the anamorphic traits and how they are now associated with a professional image.