Mounting a ND10 on a Zenitar 16 mm Fish-Eye

In case there are those who are equally foolish to pursue this idea. The Zenitar Fisheye comes with a set of film-era filters (26.5 x 0.5 mm thread) that screw into the rear of the lens. Apparently the filters are part of the optical scheme and a clear filter has to be fitted if no filter effect is required. I wanted a 10 stop ND filter for the lens and used a 26.5 x 37 step-up ring and a decent (no colour cast) glass 37 mm screw-in 10 stop grey filter (the smallest diameter I could find, Haida Slim Pro II MC ND3.0 1000x).

The amount of space in the alpha mount is very limited due to the diaphragm control lever. It is therefore not possible to accommodate the lens with step-up ring and filter screwed in series. I had to superglue the filter glass into the step-up ring and shorten the 37 mm thread to glass thickness. I also found that the internal diameter of the 26.5 thread side was too small as it interfered with the movement of the lens barrel (the lens barrel would not travel back to infinity focus) and had to grind it out.

Zenitar Fish with DIY ND10


Camera Model: SLT-A99V
Lens: Meyer-Optik Goerlitz Diaplan 1:3.5/80 V
Focal Length: 80 mm
Aperture: f/3.5
Exposure Time: 0.008 sec (1/125)
ISO: 100

Edited by Snegren - 17 June 2015 at 07:15

http://www.camera-filters.com/index.php?main_page=product_info&products_id=7844

The story continues. As I will be using the Zenitar Fish on my A7, all lens mount space related issues I had with my A99 are gone as the M42 to NEX converter has more than enough depth, allowing a stack of step-up ring and screw-in filters. As I found that a 10 stops ND filter gives about 15 seconds exposures at F16 and ISO100 on a bright day, I'll add a 3 stop ND filter to go to about 2 minute exposures.

This is easier said then done. With the lens at F2.8 and ND10 in place, the viewfinder at maximum brightness is sufficiently bright to compose the image. I seriously doubt this will be the case with ND13 installed. If ND13 is required, I will have to compose with ND10 and then add the ND3 by unscrewing the lens. A man's gotta do what a man's gotta do.

One more thing. Remotes with Minolta heritage connector that work on Sony DSLRs and SLTs don't work on A7 bodies.

I've been guilty of changing ISO as well Roger, but not satisfied with the results. ISO50 reduces dynamic range and high ISO adds noise to the already present long exposure noise, so I want to limit myself to best ISO which is 100. And as the Zenitar needs F16 for best IQ throughout the frame the only remaining variable is exposure time, which can be manipulated by changing the amount of ND stops, 0/3/10/13.

Yesterday I tried my Zenitar at F2.8 and ND13 and the viewfinder shows a murky blackness that is of no use. So wide open composing and light metering with ND10, addition of the ND3, aperture to F16, exposure calculation (base time times 260 or so) and then on the exposure timer. First result after the weekend.