What is the difference between a cine lens and a regular still camera lens?

[jamescooper18]

What is the difference between a cine lens for a 35mm camera and a regular still camera lens? Can anyone give any details on this?

- No errors that are perfectly OK on a still lens but would disrupt a video recording. This means changing one parameter may not change another. The main examples are: changing the aperture changes the focus, changing the focus changes the focal length, and for zooms changing the focal length changes the focus. This MASSIVELY complicates lens design compared to still lenses.

- T-stop instead of f-stop. Cine lenses need to have exact same transmission, the depth of field question is a perfectly secondary question. Thus they use T-stop (T for transmission) instead of f-stop. As mentioned in the video, the T-stop is also constant over the range for zoom lenses.

- Manual focus. Only manual focus is truely reliable focus. If you spend thousands, tens of thousands, hundreds of thousands or even millions on the actors, you cannot have unreliable focus. Thats also why there are always two people operating the camera - one exclusively manages perfect focus.

- Constant size. Cine lenses will often have the exact same external size in order to be able to quickly swap lenses.

- Geared. Cine lenses might be geared in order to drive them more comfortably, precisely or even electronically (as mentioned in the video, for example for smooth zooming).

Thank you for explaining in such deeper way.