With the exception of the very last one, all
the images below are the result of
stripping down and combining the optics from several lens systems
to make a hybrid macro lens.
Main lenses used were a Zeiss Vario Sonnar 10-49mm (primary) and
a Pentacon 50mm F1.4 (secondary, reverse mounted on the front
of the primary).
to be the focal lengths of the primary and secondary lenses respectively
(i.e. f1 = 49mm
in this case). Combining two suitably matched lenses
by mounting the secondary lens back to front on the primary will
cause (if both lenses are focused to infinity) the real focal
plane to be at the position the virtual focal plane would normally
occupy if the secondary were being used according to its original
design (i.e. in a camera). In other words, the region that is
brought into focus lies only a couple of centimetres from the
front element (originally the rear element of the secondary lens).
This results in images being formed on the sensor (or film)
that are f1 / f2
Approximately actual size when both primary and secondary lenses
are the same focal length. On a 12mm x 9mm sensor, the entire
image represents an area only 12mm in diameter, which clearly
allows some very interesting photographs to be taken!
As with most things, however, a compromise must be reached. At
these magnifications, depth of field is razor-thin. Using a small-sensor
camera means a smaller field of view and thus greater magnification,
but due to diffraction effects at small apertures, typically the
smallest aperture size of just a few mm equates to stopping down
only to about f/8. This further limits the depth of field,
as normally you would hope to use something around f/22.
Coupled with the obviously low light levels at small apertures,
and the short shutter times required with highly magnified live
subjects, is the fact that autofocus is largely impossible and
focus has to be achieved by moving the camera back and forth by
For more about optics and lens design, see my lens