I have encountered recently several different designs of focusing panels from Horseman 980, 985, VH, and ER-1 cameras, as well as
the monocular reflex viewer. They are all different optically and mechanically, so I think an account of this may be of some interest.
I will concentrate on the differences in measurements rather than cosmetic appearance or finer points of construction.
The oldest panels, found on the 980 and 985, with the hammer-tone finish and square button,
have six screws for two metal fixing plates, a plastic Fresnel and a separate ground glass.
The Fresnel was first installed (i.e., closest to the lens), smooth side
down (grooved side up). There is a rectangular metal spacer, made of what appears to be plated brass,
underneath the Fresnel. On the Fresnel go two metal spacers, at right and left, and finally the ground
glass, matte side down. The Fresnel is 0.071” (1.8mm) thick and its bottom side is .138” (3.5mm) from
the camera back. This puts the ground glass approx. at 0.209”(5.3mm).
The newer panels found on the VH and ER-1, with the pebbled black finish and round button,
use two plastic fixing plates held by four screws, holding the same
two optical elements, but in a different order. The ground glass is first installed, matte side down,
followed by two metal spacers at the sides, finally the Fresnel, grooved side down. The bottom
registers 0.186”(4.7mm) from the camera back. This is in accord with the info in the manuals for VH
and VH-R.
Finally, the monocular viewer focus panel, although it uses six screws and two metal clips, is constructed
like the VH panel and registered 0.187”(4.75mm). Curiously, its ground glass is a couple of millimeters
wider than the other two types and will not fit in them. This viewer has poor eye relief at the
eyepiece; this is tough on eyeglass wearers. However, a saving grace is the eyepiece takes the large round diopters that Nikon still uses!
For comparison, my two 6x9 film holders registered at 0.184-0.186”(4.7mm), when I used a piece of
ground glass in the film back to model the film plane.
As a practical matter, on camera, both backs types were sharply focused in the same plane on a subject
at medium distance. I only did this check visually with my 7X magnifier. This information could be used to check your own panels.
For instance, if you have an older panel with just the ground glass, it is probably off unless it was machined or rather thick spacers added.
the monocular reflex viewer. They are all different optically and mechanically, so I think an account of this may be of some interest.
I will concentrate on the differences in measurements rather than cosmetic appearance or finer points of construction.
The oldest panels, found on the 980 and 985, with the hammer-tone finish and square button,
have six screws for two metal fixing plates, a plastic Fresnel and a separate ground glass.
The Fresnel was first installed (i.e., closest to the lens), smooth side
down (grooved side up). There is a rectangular metal spacer, made of what appears to be plated brass,
underneath the Fresnel. On the Fresnel go two metal spacers, at right and left, and finally the ground
glass, matte side down. The Fresnel is 0.071” (1.8mm) thick and its bottom side is .138” (3.5mm) from
the camera back. This puts the ground glass approx. at 0.209”(5.3mm).
The newer panels found on the VH and ER-1, with the pebbled black finish and round button,
use two plastic fixing plates held by four screws, holding the same
two optical elements, but in a different order. The ground glass is first installed, matte side down,
followed by two metal spacers at the sides, finally the Fresnel, grooved side down. The bottom
registers 0.186”(4.7mm) from the camera back. This is in accord with the info in the manuals for VH
and VH-R.
Finally, the monocular viewer focus panel, although it uses six screws and two metal clips, is constructed
like the VH panel and registered 0.187”(4.75mm). Curiously, its ground glass is a couple of millimeters
wider than the other two types and will not fit in them. This viewer has poor eye relief at the
eyepiece; this is tough on eyeglass wearers. However, a saving grace is the eyepiece takes the large round diopters that Nikon still uses!
For comparison, my two 6x9 film holders registered at 0.184-0.186”(4.7mm), when I used a piece of
ground glass in the film back to model the film plane.
As a practical matter, on camera, both backs types were sharply focused in the same plane on a subject
at medium distance. I only did this check visually with my 7X magnifier. This information could be used to check your own panels.
For instance, if you have an older panel with just the ground glass, it is probably off unless it was machined or rather thick spacers added.