LedFx

It depends entirely on how the lens was designed, there is no general formula or way of determining the minimum focus distance. Lenses of the same focal length can have completely different minimum focus distances depending on which factors the lens designer chose to optimise.

If I know the focal length of a lens, how can I know the minimum focus distance? I know there is mark in the lens, but if I don't have the lens how can I know the MFD?

If you add extension tubes between the lens and the camera, the minimum focal distance will be shorter. That's because you change the characteristics of the lens. With enough extension tubes you can even get a negative minimum working distance (the distance between the front of the lens and the subject), i.e. it can focus behind the front lens element. That shows that you could easily build a lens with any focal length and a very short minimum focal distance, but it would also have a very short focus range.

Moodlight

Usually a long focal length means a long minimum focal distance, but that is just because a lens built that way also has other characteristics that are preferable, like having a reasonable focus range.

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.