Classic photographers who just use one lens

[Alan W]

Daguerre.

 

[BrianShaw]

Niepce.

 

[Bertil]

Bill Brandt used a Rolleiflex for at least (most?) of his portrait work, but probably more than that.
/Bertil

 

[Gerald C Koch]

Julia Margaret Cameron

 

[BrianShaw]

Demacy