Focal Length & Focusing Distance

Since I am just starting to dabble in macro, this is likely a remedial question. Is there a correlation between the focal length of a lens & its minimum focusing distance? Thank you.

Nope, not really. For two lenses that offer the same magnification, the longer focal length will give that magnification at a longer distance.

In the case of dedicated macro lenses where the minimum focus distance offers a 1:1 magnification, the longer focal length will have a longer focus distance.

krb pretty much hit the nail on the head. What lenses were you thinking about kitjv?

This was just a general question w/o reference to any particular lens.

Out of curiosity I was looking at 3 of my lenes (100mm, 50mm & 17-70mm). I noticed that the minimum focusing distance stamped on the lenses did not seem to be either positively nor negatively correlated to the focal length -- hence, my question.

But, while on the same subject ..... I was curious how the minimum focusing distance would change with the attachments of (some newly-acquired) stacked extension tubes. With my 100mm f/2.8 macro lens, the minimum focusing distance from the lens glass (not from the shutter plane) to the subject is approximately 6". With the addition of 3 stacked tubes (total 68mm), minimum focusing distance is about 4 5/8". For some reason, I thought that the stacked tubes would decrease the distance even more.

"Minimum Focusing Distance" is always stated as a distance from the film/sensor plane, not from any part of the lens itself.

The physical lens design dictates what the minimum focusing distance is going to be, and it really has nothing at all to do with the focal length other than the longer the focal length lenses are harder to design with a really close minimum focusing distance.

More than the MFD, I have known people to be more bothered about the working distance and that generally increases with focal length, although I'm sure it has less to do with focal length per se and more with their optical design.

Another aspect to understand while talking about magnification is to keep this rough rule in mind: Additional Magnification = (Extension Tube Length)/(Lens Focal Length). A smaller sensor camera will result in the same object (magnified just as much as with the same lens on a larger sensor camera) filling a larger part of the picture frame.

Thanks, everyone, for the enlightenment. I'm looking forward to putting some mileage on the new extension tubes.