Collapsible barrel lens

The closest distance is so designed at 1m on Leica old interchangeable lenses some of the later model was 0.7m. On the other hand, those for SLR body was so done at 45cm on standard lenses. Range finder construction had some disadvantage on close distance because of paralux and accuracy. This is why 1m closest distance was designed. Other rangefinder cameras were same as Leica.

I make it a rule to make this disadvantage into advantage without any irreversible modification, just an additive of an adequate extension tube. For example, Summitar extended 20 mm anteriorly could establish infinity focusing with its fuselage collapsed, without fuselage extension as normal use.

Then what will happen when the barrel was extended with extension tube? Yes, more close up shooting would be possible, 23cm distance like a macro lens!

As I show here, all the collapsible lenses could be utilized their performance shown here if an adequate length extension was applied, interesting don't you think?