Hi Marzanna,

you can use the lensmaker’s equation to estimate the focal length of a real lens, see https://en.wikipedia.org/wiki/Lens#Lensmaker's_equation. This equation links the focal length to the geometric and optical parameters of the lens: the radii of curvature of the two surfaces, the thickness, and the refractive index of the material.

If it is sufficient for your purpose to use an object that merely mimicks the behaviour of an ideal lens, you can use the “Paraxial” object type for which you can simply set the focal length.

Best regards
Benjamin

Thanks, Benjamin, very useful tips.

BW,

Marzanna