Many people decide to have three lenses. One wide,
one middle lens, and one long lens.

As a long lens I like the 180mm. lens over the 210mm.
focal length.

Having shot 35mm. and some medium format,
the 180mm. is equivalent to a 60 mm. in 35mm.
format, and the 210mm. is equivalent to a 70mm.
in 35mm. format.

It is the middle and the wide angle lens that I am not
too sure about.

As a middle lens, I feel attracted to the 120mm. and
135mm. large format lenses, but I don't know for which
one I should decant myself for. If I am right with my
equivalencies throughout this post, these two focal lengths,
for example, are equivalent to 40mm. and 45mm. in 35mm.

Then, there is the 75mm. and 90mm. lenses for
the option of a wide angle lens.

Which focal length would you choose as a wide, middle and long lens?
Which focal lengths do you like best?

The 180mm. (or 60mm. lens) is for me a better
long lens than the 210, as I don't like to be far from the
person I take the portrait from. Are you more a 210mm.
shooter or do you go even longer?

I was never a big fan of the 150mm. (or 50mm.) lens as a
middle lens. I always thought that a middle lens was
a bit wider, at 45mm. or 40mm., (or 135mm. and 140mm.
in large format). As a more general purpose lens, I find
any of these two focal lengths to be very good. I would
use any of these to take a picture of a person from the
waist up, for example, or two to six people together in a
small group, and even some landscape and architecture.

The 90mm. and 75mm. (or 30mm. and 25mm. in 35mm.
format) are interesting lenses to me for natural and architectural
landscapes. Meaning for the latter, to take pictures of
rows of houses or buildings that are less than three or four
storeys high that come out, can one say, without distortion(??).

Of course would be very interesting to try most of these
focal lengths on my own, but I think your advice could
also help me to consider in favor or against any of these
focal lengths.

Thank you very much in advance, kind regards!

P.S. These are a couple of older threads that came up in a google search: