Hologon
Hologon
Zeiss made a grip and if I remember correctly the cable release was part of the grip , to speed up shooting .
Of the ones I have seen used over many years , the grip is not necessary as you can use handheld without a cable release . Just place your hands to avoid fingers in the photograph ( only takes one roll )
As far as the neutral density filter , it is f8 without , f 16 or f32 with ,
So you use the filter outside to give even exposure to the frame .
When the light fades you remove it to actually take pictures in subdued light
Where the falloff is less noticed .
It is a great lens , the original hologon is 15mm , the g series is not as wide at 16 mm , the later g series lens focuses - the original hologon is fixed focus
Unless you have the very rare 15 mm f8 for Leica m mount which does focus ( uncoupled to rf ) which is insanely costly .
It is a modification of the goertz Hypergon large format lens from the late 1800' s. it has an additional central hourglass shaped element , added to the two spherical glass elements of the Hypergon , Zeus bought their old competier in the early 1900's and so ended up with goertz's optical designs .