[Leica] a question of perspective

[Guy Bennett <guybnt@idt.net>]

dear lugnuts,

i have a perspective question: though far from being an actual
architectural photographer, i must admit a certain fondness for the nooks
and crannies i encounter in my various ramblings. i have, on occasion, made
pictures of an attractive doorway or stairwell, courtyard or terrace, and
generally attempt to frame my shots using the brightlines as horizontal and
vertical guides. here is my question: why is it, when looking through the
viewfinder and aligning the wall/door frame/etc. with the vertical
brightline, the horizontal brightline runs at an angle to the floor/foot of
the wall/etc, though these latter items are indeed at a strict right angle
to the wall. if i frame the shot using the horizontal brightline, the same
thing happens to the vertical brightline, it will appear at an angle in
relation to the wall/doorframe/etc. i use a 50 and a 35 summicron (so it is
not a question of 'barrel' or other distortion). does anyone know why this
happens?

thanks.

guy