Bessa I focusing

[sanmich]

Hi Folks
I wander: the Bessa II is knowing for its block focussing vs lens front element focusing (through a knob on the camera that moves all the front plane)
The focusing on the Bessa I is directly on the lens rather than on the camera. does that mean that only the front element is moving?

THX

Michael

[Ernst Dinkla]

Originally Posted by sanmich

Hi Folks
I wander: the Bessa II is knowing for its block focussing vs lens front element focusing (through a knob on the camera that moves all the front plane)
The focusing on the Bessa I is directly on the lens rather than on the camera. does that mean that only the front element is moving?

THX

Michael

The postwar Bessa I has no rangefinder and focuses with the front element. The prewar Bessa RF has a similar rangefinder system the postwar Bessa II has as far as I know. Moving the the lens + lens rack in total.

Ernst Dinkla

[sanmich]

Thanks Ernst

So basically, the difference between the I and the RF/II is also a better lens? (assuming block focusing gives better results than front cell focusing)

[Ernst Dinkla]

Originally Posted by sanmich

Thanks Ernst

So basically, the difference between the I and the RF/II is also a better lens? (assuming block focusing gives better results than front cell focusing)

From memory: The only lens shared by both will be the Color Skopar f3.5. The Bessa II has the Color Heliar and the Apo Lanthar above the Color Skopar.

Front element focusing is compromising the lens to a degree as it will be at only one distance setting that it is identical to the ideal lens design the unit focusing can have. It could even be that lenses for front element focusing are adapted in their design (but keep the same basics) to that use while still carrying the same name. The slight focal length change (simple zoom effect) that helps on the job of focusing a fixed distance lens must deliver another angle of coverage too than the unit focusing one. What that type of focusing does on the field curvature is another matter. More specific on abberations etc:
http://photo.net/minox-camera-forum/007col
http://photo.net/medium-format-photography-forum/004r7H
Then there is the precision of the helix on the front element, turning around a decentered front element in worst case.
It isn't all that bad in practice.

Ernst Dinkla