This is one of the lenses that are too heavy to use, too expensive to take out of the house, and have so much zoom that you’ll never be able to find your subject. No focus rings, no option for slide in filters. Focusing is done from a knob on the back of the lens, and the filters are built into the lens. A professional could probably open up the lens and put new filters in. Aperture is fixed at f/11, which unfortunately means that adjustments have to be made by only iso and shutter speed. Degree of view is 1 degree 10 prime. It’s a mirror lens, which means the light is bounced around and around within the lens, instead of being refracted by glass. It’s for sale on ebay for US $18,300.
(total weight 25kg) was shown at Photokina 1970 for the first time, the second version with improved coating came in 1975 on the market – only very few of this lenses were made by special order only…”
I wonder what it would be like to add a 2x multiplier to this lens. A viewing degree of 55 prime. You’d need to mount a sighting mechanism on the top of this.