Image compressed horizontally — anamorphic optics squeeze information, expanded during projection with matching decompressor. Creates classic 2.4:1 cinema format with characteristic oval bokeh.
Anamorphic optics compress the horizontal image information during shooting—that's the crucial point. You shoot with a lens that squeezes the image horizontally by a factor of 2 (or 1.3x in modern variants) while preserving vertical resolution. The result initially looks distorted on the monitor: people appear narrower, objects are compressed. This is normal and intended. Only during projection or playback is the image stretched back to its natural aspect ratio of 2.4:1 or 2.35:1 by a corresponding decompressor—the classic cinema format is created.
On set, this means for you specifically: you work with a full image sensor or a 4K camera, but use anamorphic adapters or native anamorphic lenses. The advantage is that you utilize the full vertical sensor area, not just a narrow strip as with pillarboxing. This gives you more optical information, less susceptibility to moiré, and the ability to create classic cinema lighting—those characteristic horizontal lens flares and the specific bokeh characteristics that anamorphic optics bring. Many DPs choose anamorphic precisely because of these visual peculiarities: elongated flares, specific aberrations that give the image a distinctive aesthetic.
In practice, you need appropriate workflows during editing and grading: the RAW files or ProRes masters must be flagged as anamorphic so that your colorist and online editor know that decompression is pending. Many modern NLE systems handle this via metadata or explicit pixel aspect ratio settings. This used to be more complex—today it's largely automated as long as you work consistently. Important: Do not confuse with pillarboxing—that is just digital masking, not optical compression. With anamorphic lenses, you have true optical compression, which leads to more image information.
The trend of recent years: Many independent productions use anamorphic because the hardware has become affordable and the look element—that characteristic, wide cinema format with its optical peculiarities—is immediately recognizable to the viewer. It's not just format, it's style.