Mounting a front cell focusing lens on a bellows or a helicoid gives us
a lens system with adjustable charasteristics depending on the front cell
focus setting. Fixing the front cell focus at 1m or less results in an
undercorrected lens which has a peaky background bokeh and a lot of glow due to
spherical aberration,
almost like a meniscus but with a better sharpness at focus and rather little coma.
Sometimes the result is a wee bit extreme, but with practice it can be
moderated at will using the front cell, setting the softness before focusing
just like when working with an old-time soft portrait lens.
NB. most of the glow in the photos isn't lens flare but just spherical
aberration as indicated by the dependence of the halo width on the distance,
e.g., being in focus the white blouse at the lower edge of the photo #0564
causes quite negligible flare but those further off have a quite distinct,
outwards thinning halo surrounding them. The foreground column and the
background statue in #0527 also show this relationship very clearly.
Correspondingly, the black roof and the other black structures in #0533
have a very distinct black halo, and #0556 has multi-colored smearing.
The smearing can be discerned at the outlines but also affects the
insides of larger objects lending them a glow which differs from the
OOF behaviour of differently tuned lenses. This is the price which must be
paid for the high quality bokeh, completely without the glow a bokeh can
be neutral at best.
The focal length of the lens system depends on the front cell setting.
If the FL is 105 mm at the infinity setting, it must drop to
95 mm at the 1 m setting in order to achieve focus in the
original folder camera, which has a fixed lens-to-film distance and
thus must resort to changing the focal length.
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