Rodenstock 67mm Center Filter - When working with ultra-wide-angle lenses, the fall-off of illumination towards the corners is sometimes disturbing. For this reason, concentrically graduated Center Filters have been designed to compensate for this vignetting. This filter features a 1.5 stop value (5x exposure increase).
These filters have a transparency which increases gradually from the center to the edges of the filter where it reaches full transparency. The transmission is independent from the wave length of the visible spectrum.
In order to avoid over exposure and with consideration of the exposure latitude of the film emulsions, we have not fully compensated for the vignetting of the lens. It must be remembered that, when working with ultra-wide-angle lenses, one should avoid high contrast films, under-exposure, and non-uniform field illumination as much as possible.
This 67mm center filter is designed to match the angle of view and even illumination needs of the following Rodenstock APO Grandagon series of wide-angle lenses:
35mm f/4.5 Apo-Grandagon
45mm f/4.5 Apo-Grandagon
55mm f/4.5 Apo-Grandagon