Swarovision Zeiss SF side by side (1 Viewer)

henry link said:

OK, here goes. The cutaway in question can be found here:

http://www.birdforum.net/showpost.php?p=3191374&postcount=47

Starting at the ocular end. The first four lenses are the eyelens, the transfer lens (a cemented doublet here) and the field lens. Taken together these form what looks like a 4 element Konig eyepiece. That basic eyepiece is modified by the next two lenses, which are positioned between the eyepiece fieldstop and the prisms. They act like a Barlow or Smyth lens, effectively increasing the focal length of the objective and in this case are calculated to reduce the astigmatism and field curvature of the basic eyepiece. The basic eyepiece in the Zeiss SF appears to be a modified 6 element Erfle combined with a singlet ahead of the fieldstop. The use of a singlet rather than a doublet in that position probably explains the reports of edge corrections in the SF being inferior to the SV.

The next lens on the other side of the prisms is the focusing lens. In the SV it's negative (center is thinner than the edge). The focusing lens in the Zeiss SF is positive. A negative focuser increases the effective focal length of the fixed objective lenses up front, a positive focuser decreases the effective focal length. The fixed objective lenses up front in the SV form a triplet (cemented doublet air spaced from a singlet). In the Zeiss SF those lenses form a cemented doublet in a Steinheil arrangement with the negative lens first.

Click to expand...

henry link said:

OK, here goes. The cutaway in question can be found here:

http://www.birdforum.net/showpost.php?p=3191374&postcount=47

Starting at the ocular end. The first four lenses are the eyelens, the transfer lens (a cemented doublet here) and the field lens. Taken together these form what looks like a 4 element Konig eyepiece. That basic eyepiece is modified by the next two lenses, which are positioned between the eyepiece fieldstop and the prisms. They act like a Barlow or Smyth lens, effectively increasing the focal length of the objective and in this case are calculated to reduce the astigmatism and field curvature of the basic eyepiece. The basic eyepiece in the Zeiss SF appears to be a modified 6 element Erfle combined with a singlet ahead of the fieldstop. The use of a singlet rather than a doublet in that position probably explains the reports of edge corrections in the SF being inferior to the SV.

The next lens on the other side of the prisms is the focusing lens. In the SV it's negative (center is thinner than the edge). The focusing lens in the Zeiss SF is positive. A negative focuser increases the effective focal length of the fixed objective lenses up front, a positive focuser decreases the effective focal length. The fixed objective lenses up front in the SV form a triplet (cemented doublet air spaced from a singlet). In the Zeiss SF those lenses form a cemented doublet in a Steinheil arrangement with the negative lens first.

Click to expand...

henry link said:

Thanks, Suppressor. I guess I'll take that as a vote of confidence, but really I'm just an obsessed hobbyist, a creature that surely falls a link or two below regular mortals in the great chain of being.

Click to expand...

henry link said:

OK, here goes. The cutaway in question can be found here:

http://www.birdforum.net/showpost.php?p=3191374&postcount=47

Starting at the ocular end. The first four lenses are the eyelens, the transfer lens (a cemented doublet here) and the field lens. Taken together these form what looks like a 4 element Konig eyepiece. That basic eyepiece is modified by the next two lenses, which are positioned between the eyepiece fieldstop and the prisms. They act like a Barlow or Smyth lens, effectively increasing the focal length of the objective and in this case are calculated to reduce the astigmatism and field curvature of the basic eyepiece. The basic eyepiece in the Zeiss SF appears to be a modified 6 element Erfle combined with a singlet ahead of the fieldstop. The use of a singlet rather than a doublet in that position probably explains the reports of edge corrections in the SF being inferior to the SV.

The next lens on the other side of the prisms is the focusing lens. In the SV it's negative (center is thinner than the edge). The focusing lens in the Zeiss SF is positive. A negative focuser increases the effective focal length of the fixed objective lenses up front, a positive focuser decreases the effective focal length. The fixed objective lenses up front in the SV form a triplet (cemented doublet air spaced from a singlet). In the Zeiss SF those lenses form a cemented doublet in a Steinheil arrangement with the negative lens first.

Click to expand...