Pl mount for C lenses on SI-2K

[Bob Hart]

Alex.


Given the state of the euro relative to other currencies, if you can get 20 players ready to put up their cash, it might be worth a call to P+S Technik themselves to get them to quote for a production run. They already have the templates for IMS rear and C Mount inner ring. The good doctor and his team may even have designed the actual adaptor but not put it into production.

As one business outfit, they make and service a very large range of individual specialised products, all high precision but likely none will never be mass-producted at scales which will draw costs down.

Their range of compact 2/3" prime lenses ( Linos or Linhof?) are already customised to the IMS mount to get around the problems of the C Mount.

The C mount issues as you would know are :-

debateable mechanical strength,
poor resistance to wear and tear
subject to ruination of mount and/or lens due to crossthreading
slow change-out of multiple lenses
no positive lock feature (turns in mount when focussed or zoomed)

My guess is they have gone for the direct-to-IMS system because there would be inevitable complaints and comebacks with C Mount lenses. The 16mm film industry did not move on from the C Mount and ARRI standard mount without good reason.

Because P+S already provide for compact lenses, there is probably no commercial argument for another C Mount system other than the "pipe washer" already offered.

There may however be an existing IMS-C Mount CAD file sitting in the archive already, hopefully with the flange face over-cut rearwards so that lenses can be shimmed forward.

For a limited run of 20 units pre-ordered and paid for, they might be able to come up with a competitive price.

For the sake of their reputation for strong and precise work, they might want to do the adaptor as a two-part with a stainless ring and fourscrew flange containing the C Mount thread for wear and strength and to provide a facility for shimming.

This in itself becomes more complicated because the end walls of a two part design would have to be kept thin, therefore weakened compared to the "pipe washer", which is limited only by the strength of the four screws in their holes.

A one-piece mount they might want to make from stainless which would push the cost up.

They might be persuaded to do them in aluminium if some sort of indemnity against combacks for crossed threads and promise to use them only as permanent mounts for individual lenses was entered into by the buyers.

They might be willing to punch out some shim sets for the C Mount flange face as well.


Just a big post prompted by a bigger thought than I orignally intended???

[Bob Hart]

Furthur to above, I linked Silvio at P+S Technik to this thread. He would be interested know a bit more about what we have done.

I'll see if I can get a .jpg of my mount and post it here. Between the bunch, we might hopefully arrive at the most useful combination of ideas.


'FOOTNOTE - PICS ADDED INCLUDING OFFTOPIC BANDICOOT

NOTE: The mount is shown on the Min35 for convenience reasons. The SI2K is away at the moment.

My version of the mount adaptor is not usable on the Mini35 as the rim around the front cover glass on the Mini35, impinges and rides high on the rear wall of the shoulder on my mount. On most other IMS mount adaptors, there would be a large clearance hole in there.

[Alex Raskin]

Originally Posted by Bob Hart

there would be inevitable complaints and comebacks with C Mount lenses. The 16mm film industry did not move on from the C Mount and ARRI standard mount without good reason.

While PL mount is fantastic, in fairness, I never had any real issues with C mount so far. It's less convenient for sure, but it was used in the field for at least the past 40 years very successfully, so I would not just write C-mount off.

Given a choice, of course I'd always have PL mount over C though :)

[Alex Raskin]

Hi, here's my PL IMS-to-C adapter' photos.

Admittedly, not as snazzy as Bob's, without any laundry holders or small rodents - but hey, I gotta use what I have! :)~

[Bob Hart]

It is all a means to an end.

Your arrangement of putting the C Mount behind so that the loading is forwards through the mount is pretty much what I was suggesting with the two-piece design. The C mount section would likely be stainless or hard steel for thin-walled strength and resistance to cross-threading if P+S had anything to do with it. A shaved-down "pipe-washer" C mount fastened forward onto a IMS disk through the same four screw holes might be the simplest way to go about it.

Is that lens from a Panasonic VHS two-piece camera and recorder? I don't think your lens would fit on my mount because the back of body is wider if I remember correctly.

C Mount is fine for the smaller bodied prime lenses more commonly used on the SI2K but bigger lenses or zooms which have wide focus rings. zoom rings and draggy friction lube in them for smooth operating, there is too much leverage on the threaded mount and they tend to screw out when you pull focus or zoom.

If they break out off the back of the lens on the threads, what's left can be a handful to shift out of the mount. Other than that, I have to agree with you. They are as simple as it gets and the CCTV security camera manufacturers responsible for the millions or so which use C and CS Mount can't all be wrong.


The small rodent is actually a marsupial, like a kangaroo with very severely arrested development. They are pouched like a roo. They eat just about everything and will tear the stitches out of the top of your shoes trying to dig out the toe jam if you hang out clothes on the line at night.

They tear the grass up chasing lawn beetle larvae. If you throw a handful of cat pellets in low weeds, they will rotary-hoe the ground for you. Scraps of pumpkin will get the same result. They go after the earthworms which come up for the pumpkin.

They are about as adept at avoiding road traffic as the pavement itself so they don't last very long.

The ones here all have old dog bites on them, They twist in their skin when grabbed and boot a big dog in the face which amazes the dog and it lets go. Their nemesis is the fox terrier which turns them over and crushes their soft stomachs. Cat bites are like snake poison to them.

When two males get into dispute, they fight like ju-jitsu grab with their forepaws like roos. They don't then go for a gut kick, but do these weird little over-the-hip throws and one ends up on the ground, gets up and has another go.

[Alex Raskin]

"They are about as adept at avoiding road traffic as the pavement itself so they don't last very long. "

LOL awesome write-up, man.

Now I'm intrigued. What is that marsupial called? Is it a wombat?

[Alex Raskin]

...oh wait, that was a Bandicoot as per your image's name - I saw it when clicked on the image.

You know, back in the Imperial Russia they were called "Longfoot Ghost". Really.

[Bob Hart]

Their proper name is a "quenda".

They have absolutely no sense and no fear. When grown, although smaller, they will generally dominate most cats except feral toms which will still have crack at them. It is whilst they are in the in-between after pouched and fully grown that they are vulnerable to cats and of course dogs.

When crouched up feeding they look like rats. In fact a distantly related animal called a Quokka is endemic to Rottnest Island about 12 miles off Fremantle which was named by dutch explorers, Rottnest apparently being rat nest.

Their back legs stretch out a long way. When they kick off, they go like greased lightning. From the verander floor, up onto the shade-cloth, across against the end-wall, across higher against the rear wall, then out through the screen door about 6 feet off the ground when they get desperate. Like the motor cyclist in the wall of death. Mostly they just shuffle around and get inside the guts of the beer-fridge for a bit of warm on cold winter nights.

[Alex Raskin]

Bob. Don't spend so much time with Quendas. They can't be trusted.

It's like expecting competitive prices from P+S, or something.

;)

I keed, I keed

[Bob Hart]

Alex.

I thought you were going to follow up with something like, " it's un-natural, you should be spending more tme with your own kind".

Quendas - the little guys are an endangered species. They happen to be on a high presently but seem to be on a 30 year cycle according to my late father, whose theory was that when the population density reached a cetain point, a contagion would go through them. Problem is, the next one may clean them out entirely as there has been a lot of landclearing habitat change.

Competitive. The value of the euro may change that.

[Bob Hart]

Here's a link to that famous vendor starting with "e" shows a PL to C mount adaptor.


ARRI / ARRIFLEX PL ADAPTER FOR C-MOUNT LENSES - eBay (item 170507375251 end time Jul-03-10 15:13:40 PDT)

I am unsure if it would work on an IMS-Mount. The rear shoulder looks a bit deep but who knows?

Silvio at P+S Technik has advised that the subject of a IMS - C Mount adaptor has been referred to their R&D Department. I sent him a link to this thread.

[Alex Raskin]

That eBay thingy won't fit in IMS base, unfortunately.

I had to cut the flange off of that, and just use it separately with a fitting C-part.

[Alex Raskin]

Originally Posted by Bob Hart

Silvio at P+S Technik has advised that the subject of a IMS - C Mount adaptor has been referred to their R&D Department. I sent him a link to this thread.

O Silvio, where art thou

[Bob Hart]

Alex.


Just thinking an odd thought. In your arrangement, is there enough space in there to use four screws on the same centres as the original "pipe washer" but with small coil springs and sockets under them so that an awkward but usable backfocus adjustment coud be had. This would be a C mount plate mounted behind the IMS disk and the screws clamping the C mount forward against firm spring pressure.

A bonus would be in being able to also skew the mount for an effect as in perspective control with deep depth of field chosen with a normal-view lens.

[Alex Raskin]

Hey Bob, this could work technically.

But this will also make everything more complicated - from making such adapter to using it, IMO...

My personal goal in making this adapter was to rather uncomplicate things :)