Getting a Schneider Arri Wide Angle Lens on a CP-16R
Posted 11 August 2016 - 02:01 PM
The back little lens just pops out. I'm wondering if I at this point I should just glue it in and dremel down the edge of the ring of that little back lens to get that last 0.5mm closer or whatever it is I need.
The rear element is pretty much kissing the shutter so I feel like I have nothing to lose at this point. Ideas/suggestions?
Thanks in advance.
Posted 11 August 2016 - 02:20 PM
I have a 25mm in that configuration, and I was advised that the later serial number do not interfere. I don't know what the difference is. It seems that on some of the Russian counterparts, they did exactly this; cut a big diagonal section out of the bottom of the lens so it would not interfere with the mirror.
If you try it I would love to know your success - Need to try it on my 25mm....
Posted 12 August 2016 - 07:59 AM
Might be fun to get a hold of a cheap one just to see if I can get that lens to back off the shutter somehow, to get infinity, so I don't have to mess with the actual lens much.
I just don't know all the calculations involved. I'll post my results though.
An interesting side note: a modern canon ef lens has a bayonet rear which fits in my CP mount, albeit with tape. It doesn't sit back close enough for a normal FFD, but any Canon lens becomes a good close up lens for cheap...!
Posted 14 August 2016 - 02:07 PM
Can't believe I got this lens enough away from the shutter but I did.
After removing the collar of course, it's just a matter of filing down the sides of the little lens that pops out.
Don't be like me and try to glue it in though, there's a whole seperate story involving off gassing of glue and other complications. Just tape it with something that barely catches it.
Jay, I'm jealous you have a 25mm lens, that's what I need next, but good luck, it can be done!
Posted 15 August 2016 - 12:33 AM
After the Arriflex 16BL came out in 1965 with a slightly reduced mirror clearance than the earlier 16S, many Standard mount lenses for 16mm format no longer fitted the later Arri cameras without hitting the mirror. The only 16mm lenses that the 16BL manual lists are the Schneider Cinegon f/1.8 10mm from 1967 onwards (which I believe is from serial no 9861936 and up) and the Zeiss Distagon f/2 8mm. I'm pretty sure Schneider also later modified their 16 and 25 lenses but I don't know the serial numbers.
Here's an early version of the 10mm with the rear element well within the rear housing:
Compared to a later version that clears the mirror with a much reduced rear element cowling and a rather exposed element:
I don't know how closely the CP-16R mirror clearance matches that of a 16BL, but it must be pretty similar.
I've seen lots of examples of the rear of a lens filed or machined down with a bevel to clear a mirror, some were done better than others.
Posted 15 August 2016 - 02:24 AM
Great information Dom!
I sure learned a lot by having and solving this problem, at many points i thought it was hopeless, but it's pretty exciting to have that sucker sit in there and focus.
I've been aware that there was some type of 'jump' in serial numbers for the Schneider when the rear element gets smaller, I for some reason thought it was around #8,000,000 or so judging by all the photos I've seen on eBay....
Nevertheless, I can almost tell now from a photo whether a lens will clear the shutter for my Cp-16R- just by looking.
It's so tricky 'cause all this is going on inside an area that you can't see at all. I suppose now I could just measure my new filed-down back element distance and ask any potential lens seller to check that it's the same or less before making any further lens purchases.
So I can concentrate on actually making films.
Posted 15 August 2016 - 07:20 AM
Could you post a picture of the complete job? I would love to give it a go on my 25mm.
Posted 16 August 2016 - 11:17 PM
HOW TO FILE (AND NOT) DOWN A LENS WITH A BARELY TOO LONG BACK ELEMENT FOR A CP-16R
(A Photo Essay with Pictures)
With the filed (dremel) down 'collar' next to it that fell off after I tried removing it other nutty ways:
Yeah, that's clear tape holding the edges on, it may look stupid but it works. I tried gluing and it was a disaster from off-gassing into the inner element, I actually broke the outer edges of one of the little lenses in there by drilling and, well somehow- 'cause I guess I only need the center of the lens- it's OK.
Because there's such a HUGE DEMAND for filing down obscure wide angle lenses for CP-16R 16mm film cameras, I'm now available to file down and tape lenses for such users at the unbelievable low price of 99 CENTS + TAX. I take Discover and all Library Cards.
Posted 17 August 2016 - 08:05 AM
Yes, it sure does.
I have an Arri to CP adapter attached w/ grub screws. That sits on the lens, in the mount and as you focus towards infinity that back element rotates, moving just a tiny (say 1mm or less I guess) bit closer towards the shutter.
With the original collar around the back element and the adapter all the way on, you can't even get the lens in the mount.
After removing the collar, I got it on and- using my inching knob, could focus halfway to maybe 1.5'. I could feel that back element kissing the shutter.
So I just kept filing away at the sort of hard yellow edge of that tiny lens on the back and boom! It was all I needed,
If I ever have to do it again though I'll be patient and wait 'till I have a proper size tiny screwdriver for removing that back collar so I don't strip it!
Posted 17 August 2016 - 09:01 AM
That lens appears to be constructed differently than mine. The rear element is held in with three screws (adjusts back focus? surely not...) so I'm a bit confused on the process for this specific lens.
My lens is bayonet mount, so it does not rotate while focusing.
Posted 17 August 2016 - 10:01 AM
Well I don't think you have anything to lose by removing the collar, assuming it's making your back element bigger. Does it look like it can come off? Is there even a collar?
As you can see by my first photo, the whole rear element on a 10mm Schneider unscrews as well.
I'd need to see a photo if it's drastically different, if you'd like my feedback.
I didn't dare touch any part of the main lens BTW, on the advice of Jean-Louis.
The main thing is to find a safe sensible way to get anything protruding -away from the shutter, as I'm sure you realize.
Posted 22 August 2016 - 09:04 AM
Please see the attached file.
The large part doesn't move, the small part moves in and out and interfaces with the mirror - and possibly the ground glass holder; but, as I can't see anything LOL, I don't really know.
Posted 22 August 2016 - 11:26 AM
I think if you unscrew that middle large element part you might get a better idea of what's going on.
It doesn't look any longer than mine, the question is: can that tiny black collar around the last element be removed or filed down.
I think you can safely find out either way by unscrewing the large part between the arri mount and the small last element.
Let me know if I can help more
Posted 22 August 2016 - 11:38 AM
I had nothing to lose by trying and it worked out somehow.
Posted 25 August 2016 - 03:12 PM
So the little black deal on the back holds the rear element in. Did you just tape yours in?
I could try that.
Needs more testing.
Posted 25 August 2016 - 04:55 PM
Yeah, believe it or not I taped it with strong clear tape just catching the edge of the lens. Whatever works, right?