Is camera lens value basically the same as FOV?

I am trying to understand how to zoom in/out in the scene, so I am asking here someone who knows, if the lens value is the same as FOV/Zoom value in other softwares (I am working with Cycles standalone clone from other developer but it has no dedicated FOV command line parameter, but I found out that when I change the lens value it basically do the same as FOV…or am I wrong?).

Unfortunately, there is noone there on their forums that could answer this type of question for me, so I am asking here at the original place of Cycles renderer.

  • is camera lens value basically equivalent to zoom?

  • …that is camera distance form object?

  • …cos from my test it is exactly that: a camera zoom, basically, but I would like to hear it form ppl that actually know Cycles well enough.

  • I am not talking about the camera Matrix, cos changing distance there would also affect the camera aperture values. I need really just the zoom in/out (equivalent of FOV)

Blender Lens value is focal length.

Field of View (FOV) is defined by the focal length of the lens and the camera sensor size.

Zoom is a term that defines lenses that have a changeable focal length. There are prime lenses (fixed focal length) and zoom lenses. What you call camera zoom is the effect of changing the focal length while recording.

You can match other softwares by matching Lens / Focal Length or FOV (by changing Lens unit to Field of View).

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So, it is what I thought, basically, rendering software speaking: if I change the camera lens value I get the same result as changing the FOV value in other rendering software, right (that is what it looks like when I test it and also it is how I understood your reply)?

That is: lens value is basically telling us how far the camera is from the object (visually/render speaking) without affecting camera aperture values - correct (that is how ti behaves in my tests)?

Yes, just keep in mind that the Camera Sensor Size plays a role in the conversion from Focal length to FOV.

No, focal length is the distance between the sensor plane and the focal point where rays converge inside the lens. It is in millimeters and does not represent the distance between the camera and the object.
Example: a camera 5 meters away from the subject with a 50mm lens is not the same as a camera 10 meters away from the subject with a 100mm lens.

If your camera doesn’t move, focal length acts like a crop in your image.
If your camera moves to compensate for the framing change induced by the focal length adjustment, focal lengths controls perspective compression (what we call dolly zoom, or vertigo effect)