35mm adaptor on a 2/3" chip

[Chris Brearley]

Has anyone used an SGPro/Letus/Brevis or similar adapter on a camera with a 2/3" chip? All I hear is people saying that this won't work and you need a Pro35 but I've used an RNG35 with a canon 50mm f1.4 on a Sony HDW-750p and it worked beautifully - no vignetting and only a very small loss of sharpness at the edges. A also hear a lot of people asking what the point is because of the 2/3 chip being fairly big anyway, but it still only half the size of 35mm and I have yet to come across any cheap primes for a B-4 mount! Is it because most people who own a 2/3 in cam you would expect to have the money to rent/purchase a Pro35? Anyone have any thoughts? Cheers

ps If anyone is interested - Sony Z7, SGPro and Nikon f mount footage LazyBaby "Good Girl" on Vimeo

[Bob Hart]

Here is a link to an very short clip which was a test of the Extreme on a SI2K via a hacked relay which consisted of a 58mm Noct-Nikkor which is about as sharp as a wide-open 35mm stills lens gets.

It would possibly work with a 50mm f1.4 Nikon but the optical path of the Extreme might need to be fine tuned.

LETUS EXTREME TO SI2K CAMERA TEST. By Bob Hart On ExposureRoom

The achromatic dioptre fitted to the Extreme was the Sony EX1 version.

My first initial impression was amazement at the ability of the SI2K camera to see into shadow areas and creases of black suit jackets. Use of a 35mm adaptor on a SI2K does not realise the remarkable resolution available from this camera. With a proper relay lens, not my hack, there would be an improved resolution but the limitation of any groundglass remains.

The Extreme offers an advantage in that the larger groundglass area enables a higher potential apparent resolution. I will have to let Dennis and Wayne comment on their own adaptors as I have had no hands-on with those. I understand the SGPro and the new Blade may have a large groundglass. I also understand that the Brevis also has a large groundglass.

[Chris Brearley]

That certainly does look and I see what you mean about the blacks. Are there any more examples anywhere and do you know how the speedgrade colour space differs from 4:4:4? Unfortunately I have no idea where to start in hacking a relay lens! Do you have any plans to market this kind of adaptor? :) Thanks

[Bob Hart]

So far as I know, I am the only clown who has been silly enough to try it on the SI2K. This thread contains my account of this test :-

http://www.dvinfo.net/conf/let-us-di...reme-si2k.html


There is some images of it fitted up to a CP16R film camera here :-

http://www.dvinfo.net/conf/let-us-di...lm-camera.html


I have no intention to make or market any such adaptor. Its up to Le brothers and the other builder-vendors if it is a place they want to go.

The hack for the SI2K is simple enough. All that is required is a P+S universal mount system which is native to the SI2K and the P+S Nikon mount, then a simple adaptor ring for the Extreme which has the grub screws and shoulder on one end and an inner filter threaded shoulder for the front-end of the Nikon lens.

(ADDED TEXT - The adaptor ring would have to made up by a machine shop if you do not have the skills or equipment. It would be no big task. An existing Letus mount ring provides the template for the Letus Side. Your chosen relay lens, Nikon 50mm f1.4, or Nikon 55mm f1.2 or Noct-Nikkor 58mm f1.2 or other brands provides the template for the filter mount thread. On the Nikons it is 52mm diameter and I think 0.7mm thread pitch. You need to have the chosen lens handy so that the machinist can fine tune the thread depth to the lens as there is sometimes some variation according to wear and tear or a slightly flattened edge from being bumped or dropped. Lube the threads when fine tuning the thread depth as the aluminium of the lens thread may gall if the fit is tight and you then have a problem. Stick a piece of thick paper or plastic over the front glass to protect it when going anywhere near machinery with it. )

The Letus Extreme original cine bundle just fits up to the SI2K with the wedgeplate mount set to just enough above the bridgepieces to allow the wedgeplate lever screw to be clear to tighten the wedgeplate.

[Dennis Wood]

We've been working on exactly what you're looking for over the last 18 months. Our 2/3" multi-format B4 relay lens is nearing completion with announcements coming over the next month or so. Scarlet's announcement of a 2/3" brain was good news for us today :-)

Cheers,
Dennis Wood
www.cinevate.com

[Bob Hart]

Dennis.


Will you be doing a P+S Technik universal mount version of your 2/3"? Maybe there would be an expensive licencing issue for the mount system. A PL-Mount version would be the next best bet in terms of work room around the lens body. The SI2K would benefit from a wide groundglass view with 2/3" relay. My initial vandalism in this direction does not look too bad on the Letus with a Nikon prime doing the relay. I imagine a purposed relay lens will work a whole lot better.