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C-mount adapters


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#1 JB Guillot

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Posted 20 March 2007 - 08:11 AM

Hi Super 8 freaks !

I recently went to some photo/cine exhibition and I have seen some C-mount to photo mount (Nikon or Leicaflex) adapter.
I wanted to have some more info about such products :
- do some of you use such items ?
- what about optical quality ?
- what about conversion factors between SLR and Super 8 ? (if I use a 28mm SLR lens what will it be in S8 ?)
- isn't there some risk for the camera if used with "big" zooms ?
- ...

Waiting for your answers/experience...

Gybe
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#2 Douglas Hunter

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Posted 20 March 2007 - 01:26 PM

I purchased a C mount to nikon unit. I shot a test, using it but have yet to see the results. If I'm not mistaken when used on a S8 camera a 35mm lens is going to be about 4 times longer on a super 8 camera.

a 20mm 35 lens = 40mm if used on a 16mm camera = 80mm if used on a s8 camera.

What big zoom would you want to use on a s8 camera? Think about it, if you want to do wildlife shooting on s8 and you put a commonly available (and not very heavy) 300mm 35 SLR lens on your camera your effective focal length would be about 1200mm!

Edited by Douglas Hunter, 20 March 2007 - 01:30 PM.

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#3 Eric Dinger

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Posted 20 March 2007 - 01:49 PM

- what about conversion factors between SLR and Super 8 ? (if I use a 28mm SLR lens what will it be in S8 ?)


Gahh this again. A 28mm is a 28mm no matter what format it is in. If you have a zoom lens on you camera now, put it at 28mm and it will be the same FOV as with a 28mm SLR lens and adaptor.

Where all the 2x ,4x, equivlent stuff comes in is comparing the FOV between different formats.
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#4 Alessandro Machi

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Posted 20 March 2007 - 02:48 PM

Gahh this again. A 28mm is a 28mm no matter what format it is in. If you have a zoom lens on you camera now, put it at 28mm and it will be the same FOV as with a 28mm SLR lens and adaptor.

Where all the 2x ,4x, equivalent stuff comes in is comparing the FOV between different formats.


lol. I remember this type of discussion from a while ago.

So a 28mm lens on a 35mm camera is like a 6 - 7mm on a Super-8 camera?

But when you take a 28mm lens from a 35mm camera and put it on a Super-8 camera, it's still a 28mm lens on a super-8 camera. But a 28mm on a super-8 camera is four times the enlargement of a 6 - 7mm super-8 lens.
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#5 Bernhard Zitz

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Posted 20 March 2007 - 03:00 PM

- what about conversion factors between SLR and Super 8 ? (if I use a 28mm SLR lens what will it be in S8 ?


it's between 6 and 6.5 it depends if you take the width or height in account. Super8 aspectratio is 1.36/1, 35mmSLR is 1.5/1. I guess 6.25 is a good value...

with a 50mm on SLR you'd see about the same thing as with a 8mm on a Super8, or with a 200m on Super8 you'd see the same as with a 1250mm on a SLR, etc...

isn't there some risk for the camera if used with "big" zooms ?

I wouldn't put heavy lenses without support item on a c-mount. Specially not on a 4008ZMII, this mount is not very robust... Long SLR-lenses often come with a build in trypod-mount, try to use this... or DIY some support item like bars, a board made of wood, what ever...

cheers, Bernhard
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#6 JB Guillot

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Posted 20 March 2007 - 03:01 PM

Gahh this again. A 28mm is a 28mm no matter what format it is in. If you have a zoom lens on you camera now, put it at 28mm and it will be the same FOV as with a 28mm SLR lens and adaptor.

Yep sorry I know that :rolleyes: ...BUT as I'm not a native English speaker I lack some technical vocab and use some shortcuts to try to express myself (sorry 'bout that :( ).

Question was indeed about some "conversion" but not directly in the FOV (focal ?) but virtually : ok, that's true the FOV does not varry but the "viewing angle" (what you really see thru the lens) varries if you use a Super 8 cam instead of a SLR and if you transfort this angle into some "virtual FOV" you get some "equivalent" in S8 for a SLR lens...
I finally found some magic formula in the web to make those conversions...

Using this conversion method I indeed understood that using some long focal (SLR basis) would be insane in S8 (who need a 7000mm :lol: ...not me) so I am now wondering if such adaptaters are really helful (could help in getting long focal with my SLR lenses but as I really like wide angles :rolleyes: )

Anyway, part of my question was also to have a feedback from users about their use of it (what about macro stuff available for cheap for SLR used on S8 cams ?...) or anything that could help me and others to have a precise idea of what those adapters are good at :D

Thanks for your help ;)
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#7 Bernhard Zitz

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Posted 20 March 2007 - 03:09 PM

so I am now wondering if such adaptaters are really helful

I used a long SLR-lens on a Super8 to film the moon :D
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#8 Eric Dinger

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Posted 20 March 2007 - 10:42 PM

Sorry if I seemed annoyed earlier, it's just that this comes up regularly, and I've stopped trying to compare one format to the other, seeing as I use so many, I just remember what is 'normal' for the format and figure out what I want from there.

JB there aren't many wide angles for 35mm SLR's that are 'wide' in super8, the only one I can think of is the peleng 8mm. So no they aren't very useful in that regard. If you want macro lenses I would look for one in the 50-60mm range, fairly long on super8 but manageable with a good tripod. You can really look in any of the old mounts, something in m42 should be cheap and easy to find.

FOV = Field Of View.
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#9 JB Guillot

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Posted 21 March 2007 - 07:45 AM

Sorry if I seemed annoyed earlier, it's just that this comes up regularly...

No problem...and thanks for your post anyway...it's true that you don't need to compare but when you start (just as I do) using some format, you need to find some references and I could not really find my marks find Super8 data only...I needed some "tool" to help me. Now I recently found the magic formula that can help me...

JB there aren't many wide angles for 35mm SLR's that are 'wide' in super8, the only one I can think of is the peleng 8mm.

:o I searched on the web for this Peleng lens...seems to be funny for my SLR :D

You can really look in any of the old mounts, something in m42 should be cheap and easy to find.

This comes near to my next question : when it comes to C-mount it seems that there are different size of C-mount...am I wrong ?
m42 is a screw mount (C-mount too ?), right ? But will it fit some Beaulieu with C-mount...

Man, I feel so bad at understanding those mount stuff...so difficult to find some clear info 'bout old stuff like that <_<

FOV = Field Of View.

Thanks ;)
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#10 chuck colburn

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Posted 21 March 2007 - 01:10 PM

No problem...and thanks for your post anyway...it's true that you don't need to compare but when you start (just as I do) using some format, you need to find some references and I could not really find my marks find Super8 data only...I needed some "tool" to help me. Now I recently found the magic formula that can help me...
:o I searched on the web for this Peleng lens...seems to be funny for my SLR :D
This comes near to my next question : when it comes to C-mount it seems that there are different size of C-mount...am I wrong ?
m42 is a screw mount (C-mount too ?), right ? But will it fit some Beaulieu with C-mount...

Man, I feel so bad at understanding those mount stuff...so difficult to find some clear info 'bout old stuff like that <_<
Thanks ;)


Hi JB,

A "C" mount is 1 inch diameter by 32 t.p.i. (threads per inch) and has a flange focal depth of .690 inch.
There is/was similar mount called a "CS" mount that used an adapter that was left on the camera to which various lenses attached.
A M42 mount is also a screw mount that is/was used on 35mm still cameras (think Pentax, Praktica, etc.) This is 42mm diameter by 1mm pitch (t.p.i.) and has a flange focal depth of 45.46mm.
So you can go from "M42" (or any other still camera lens) to "C" mount, you can't go the other way around.
Just as a point of intrest, mount converters always used to be listed as lens mount first and camera mount second. As in Nikon to C mount etc. This prevented confusion as to which lens and which camera one was refering to.

Chuck
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#11 Bernhard Zitz

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Posted 21 March 2007 - 01:12 PM

m42 is a screw mount (C-mount too ?), right ?


m42 is this http://en.wikipedia..../M42_lens_mount

and C-mount is this http://en.wikipedia.org/wiki/C-mount

But will it fit some Beaulieu with C-mount...


there are m42 to C-mount adapters, with such an item a m42-lens would fit on a beaulieu with c-mount

Edited by Bernhard Zitz, 21 March 2007 - 01:13 PM.

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#12 JB Guillot

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Posted 21 March 2007 - 01:30 PM

Wow...thanks for your help, explanation and links (French - yes I'm French - version of wiki doesnt have those topics <_< ).

So I might have to look for a m42 to C-mount adapter which would work with my old (very old !) SLR lens.

Thanks once again ! :)
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#13 Bernhard Zitz

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Posted 22 March 2007 - 05:22 AM

So I might have to look for a m42 to C-mount adapter which would work with my old (very old !) SLR lens.


I have such an adapter to use my takumars on 16mm-cameras, it works fine...

Are you shure that your lens is m42? m42 is the most common but there are other screw-mounts like T2 or m39 (old leica)

Bernhard

Edited by Bernhard Zitz, 22 March 2007 - 05:23 AM.

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#14 JB Guillot

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Posted 22 March 2007 - 07:35 AM

Are you shure that your lens is m42? m42 is the most common but there are other screw-mounts like T2 or m39 (old leica)

Yes I'm sure ! Old Pentax screw mount is m42.

I found a m42/C-mount adapter on the web but it seems quite...strange : here

If some of you have some references I could use to find one...(I must have seen one on an old Pentax catalog but)
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#15 Bernhard Zitz

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Posted 22 March 2007 - 10:40 AM

I found a m42/C-mount adapter on the web but it seems quite...strange : here

this one looks fine, and the price is reasonable too...
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#16 JB Guillot

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Posted 24 March 2007 - 05:39 AM

Another question 'bout C-mount stuff :
There are some C-mount lenses that are produced for video cameras (surveillance cameras and such), is it possible to use thoses lenses on a Super 8 C-mount Cam ? Pros ans cons of doing so ?

Here is an example of such lens. SOme of them have manual Iris which is fine but they seem to b elinked with a specific CCD format (1/4" in my example but there are some 1/2 and 1/3 models too). Some explanation/advice/point of view would be interesting ;)

Thanks for your help *newbie inside*
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#17 Bernhard Zitz

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Posted 24 March 2007 - 07:22 AM

Another question 'bout C-mount stuff :
There are some C-mount lenses that are produced for video cameras (surveillance cameras and such), is it possible to use thoses lenses on a Super 8 C-mount Cam ?


yes it is possible, but some shorter lenses (normaly 8mm and shorter) go deep in to the camera, that they would touch the shutter or the prisme. Also watch out not to get a cs-mount, it has different focal flange distance...
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#18 JB Guillot

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Posted 24 March 2009 - 06:07 AM

Back with this old topic...

I finally found a Canon FD > C-mount adapter.

Last week-end I finally had enough time to test this stuff with a Canon FD 70-210 f:4 lens i found on Ebay.
The lens is clear and seemed to work fine : zoom moves with no pain and aperture ring moves easily. The problem comes when I mount the lens on the adapter : aperture automatically opens (when rotating on the adapter) to full aperture. Once everything is ready to film, I can't change the aperture...fully opened is what I have.

Do you have the same experience with same/other adapter ? Does it seems "normal" ?

Few details :
- When lens is not mounted on anything, turning the diaph ring doesn't do anything. Aperture stays half-opened.
- when mouting the lens on the adapter (rotating), diaph opens
- once mounted, aperture stays fully opened whatever the aperture ring's position...

Of course I can always trick the light meter with neutral grey filters...but it's not really easy.

Any piece of info on that topic would be great.

Thanks for your help.
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#19 Tim Tyler

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Posted 24 March 2009 - 09:56 AM

The problem comes when I mount the lens on the adapter : aperture automatically opens...


There is a sliding key protrusion on the back of the FD lens. You can apply gentle pressure with your finger when the lens is not mounted and slide the key in one direction. When released, a spring pushes it back.

Trim a toothpick to the length of the channel space when the key is slid fully to one side. Slide the key with your finger and insert the toothpick into the channel, preventing the spring from returning the key to its default, unmounted position. The iris ring will control the aperture now.

Then change the JB in your display name to your real first name.
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#20 Bart Smith

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Posted 24 March 2009 - 02:00 PM

Canon made a 'Manual Diaphragm Adapter' to address this problem, but it is much easier and cheaper to buy a toothpick and do as Tim suggests...
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