Fujinon f0.85 20mm

putorc · Joined: 16 Apr 2014 Posts: 5

Hi folks,
I recently picked up a rare fujinon 20mm f.085 lens and am trying to find out more about it. I own a small cmount 25mm f0.85 fujinon that I like and I am hoping this has a similar optical quality although this lens is much much larger. Also trying to work out how to mount it to the digital bolex cmount (the lens has a rear thread of 49mm), I've had success mounting m42 lenses with an adapter, my current plan is to use the c-mount to m42 (42mm) adapter and step up to 49mm but the step ring will take a long time to arrive, putting me outside the return window, thus why i'm trying to suss out the quality and mountability of the lens in the mean time. Any info appreciated, thanks!

Measurements as follows:
Image Diameter: approx. 20mm
Rear flange distance: 13mm (from the rear flat barrel surface to the image plane).
The rear thread extends out 6mm, so the distance from the rear of the thread to the image plane is 7mm.
Filter Thread: 52mm
Mounting thread: 49mm x 0.75mm pitch
Weight: 1 lb. 15 oz. (0.9kg)

Fabian · Joined: 04 Dec 2011 Posts: 254

Make another post to show the pictures and I'll edit them out of mine. (anti-spam-measure)

kds315* · Expire: 2021-03-09

I have a feeling this is a special lens. What EXACTLY is completely written on the front ring?
13mm back focal length is non-standard for a c-mount lens.

putorc · Joined: 16 Apr 2014 Posts: 5

kds315* · Expire: 2021-03-09

Well, why don't you trust the seller (I know him), as he wrote in the auction Click here to see on Ebay :

(quote)
Fujinon Ultra-fast Lens 20mm/f0.85

This is an extremely rare lens. I have never come across one before in 20+ years of using similar lenses.
It is a shorter focal length (20mm) than the well-known Fujinon 25mm/f0.85, so has a wider field of view and maintains the ultra-fast speed of f0.85
It is a much larger and quality built-lens than the 25mm/f0.85

The lens is as new, with no glass or coating problems, no scratches or marks on the barrel.

Image Diameter: approx. 20mm
Rear flange distance: 13mm (from the rear flat barrel surface to the image plane).
The rear thread extends out 6mm, so the distance from the rear of the thread to the image plane is 7mm.
Filter Thread: 52mm
Mounting thread: 49mm x 0.75mm pitch
Weight: 1 lb. 15 oz. (0.9kg)
(unquote)

putorc · Joined: 16 Apr 2014 Posts: 5

I've no issue with the seller or listing at all, that is where i posted the measurements from. He is also unsure what type of lens it is, only that it has a 49mm mounting thread.

If you read my OP this is not a c-mount lens.

I was saying I own a cmount 25mm fujinon 0.85 (similar specs) which is a great lens, this 20mm Fujinon 0.85 is a much bigger lens and I am hoping to determine it's optical qaulity, origins and the likelyhood of it pairing with the digital bolex as successfully as the 25mm cmount.

kds315* · Expire: 2021-03-09

I would guess it is a special lens possible for an image intensifier system, the speed would indicate that.
Another idea would be an early chipmaking lens, but usually these lenses have no aperture or at least
cannot be stopped down too much (to avoid diffraction).

Pairing it with a Bolex will not be possible with this short register length.

putorc · Joined: 16 Apr 2014 Posts: 5

Sounds like a lost cause then. I will have to return it.

Thanks for the info!

kds315* · Expire: 2021-03-09

Return it? for what reason? Is something wrong with it?
The seller has more than precisely described the lens...

(btw. using the seller's images in light of current copyright laws is not good style)

putorc · Joined: 16 Apr 2014 Posts: 5

[quote="kds315*"]Return it? for what reason? Is something wrong with it?
The seller has more than precisely described the lens...

For.. none of your business it's a private transaction?

Benjamin Vu · Joined: 03 Jan 2014 Posts: 10

Don't return the lens since it a rare find.
Get an adapter and get some pictures out of it.
That was all the fun about.