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Projection lenses - my method of adapting with focusing
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PostPosted: Fri Apr 14, 2017 11:13 am    Post subject: Projection lenses - my method of adapting with focusing Reply with quote
Finally I've found some time to adapt projection lenses using my currently favorite method to usable form, with functional focusing. In short - you need to make helical groove on lens' body and craft (or reuse) sleeve with lens' guiding pin. On the end of the sleeve you can place any mount you need - M42, M39, C-mount etc. (meeting proper flange focal distance).

Here are two quick examples.

Visionar 130/1.9, M42 mount:



Sample photo, Sony A7R, no post-processing besides resizing:


Triplet-5M 100/2.8:



Sample photo, Sony A7R, no post-processing besides resizing:


I also adapted a few big and heavy LOMO 100/2 (and similar).

Pros:
1. Cheap materials (you don't need to pay for helicoid, reductions etc., you only nee some aluminum)
2. You can use very heavy lens (no problem with friction caused by helicoid's bending)
3. You don't waste precious space between lens' back and flange for placing helicoid, especially important when lens has large diameter (larger than helicoid's opening) or short flange focal distance
4. Very long range of longitudinal lens movement while focusing, nearly as long as lens itself

Cons:
1. You need skillful serviceman with lathe
2. Focusing is not perfectly tight and smooth (but also many cheap Chinese helicoids I used had that problem)


PostPosted: Fri Apr 14, 2017 5:15 pm    Post subject: Reply with quote
Brilliant!

Like 1 Like 1


PostPosted: Fri Apr 14, 2017 5:20 pm    Post subject: Reply with quote
Nice work!

But this is the main problem -

"1. You need skillful serviceman with lathe "

Cutting helicals like that is not a typical job.


PostPosted: Fri Apr 14, 2017 5:53 pm    Post subject: Reply with quote
That's an excellent mount, I like it. But the other option is to cannibalise an old projector, some have the helicoid that is usable for this application. I've got an old Gnome projector that I think will make a suitable lens mount. Next project maybe?


PostPosted: Fri Apr 14, 2017 6:31 pm    Post subject: Reply with quote
Thanks! Making this groove indeed needs not only experienced lathe operator but also proper lathe.
This type of conversion I use only when there is no helicoid from projector. I reuse them whenever I can, I especially like Leitz devices - sometimes their helicoids work as smooth and precise as regular lenses.


PostPosted: Fri Apr 14, 2017 7:13 pm    Post subject: Reply with quote
Thank You Dog


PostPosted: Fri Apr 14, 2017 8:16 pm    Post subject: Reply with quote
A sales pitch it is? These are currently offered on ebay for sale....hence why I'm asking Twisted Evil

I moved you other threads to the Lens Sales section where they belong!

A few questions:
- why need to damage the original lens by cutting groves into it, risking the optics inside?
- such a grove causes not very smooth focusing - why not use a cheap M65 helicoid costing $30 on ebay? Weight is anyway not carried by the camera but by holding the lens?
- what's the benefit of a rotating front lens (for instance if one wants to use a polarizing filter)?
- why show this solution here if basically only you and your mechanic are able to provide that? ---> "clever" sales pitch??

Last edited by kds315* on Fri Apr 14, 2017 8:58 pm; edited 1 time in total


PostPosted: Fri Apr 14, 2017 8:50 pm    Post subject: Reply with quote
kds315* wrote:
A sales pitch it is? These are currently offered on ebay for sale....hence why I'm asking Twisted Evil

I moved you other threads to the Lens Sales section where they belong!

A few questions:
- why need to damage the original lens by cutting groves into it, risking the optics inside?
- such a grove causes not very smooth focusing - why not use a cheap M65 helicoid costing $30 on ebay? Weight is anyway not carried by the camera but by holding the lens?
- what's the benefit of a rotating front lens (for instance if one wants to use a polarizing filter)?
- why show this solution here if basically only you and your mechanic are able to provide that? ---> "clever" sales pitch??


I can answer the questions about "Sales pitch?" No, there is no sales pitch here, none whatsoever. Besides, what business is going to publish their how-to? Come on...


PostPosted: Fri Apr 14, 2017 8:58 pm    Post subject: Reply with quote
visualopsins wrote:
kds315* wrote:
A sales pitch it is? These are currently offered on ebay for sale....hence why I'm asking Twisted Evil

I moved you other thread to the Lens Sales section where they belong!

A few questions:
- why need to damage the original lens by cutting groves into it, risking the optics inside?
- such a grove causes not very smooth focusing - why not use a cheap M65 helicoid costing $30 on ebay? Weight is anyway not carried by the camera but by holding the lens?
- what's the benefit of a rotating front lens (for instance if one wants to use a polarizing filter)?
- why show this solution here if basically only you and your mechanic are able to provide that? ---> "clever" sales pitch??


I can answer the questions about "Sales pitch?" No, there is no sales pitch here, none whatsoever. Besides, what business is going to publish their how-to? Come on...


Well, I just moved two threads into the Lens Sales section with the ebay auction link added to it Wink

I left this one here as it shows the way it was adapted, for information, certainly worth knowing about!

Last edited by kds315* on Fri Apr 14, 2017 8:59 pm; edited 1 time in total


PostPosted: Fri Apr 14, 2017 8:58 pm    Post subject: Reply with quote
It's presentation of a versatile method that I was looking for. No matter if I want to adapt RO-109-1A 50/1.2, Visionar 130/1.9, Visionar 200/1.9, Lomo RO502-1 110/2 - method is the same (I can't imagine adapting Visionar 200/1.9 with cheap M65 helicoid). Consequences described in questions 1, 2 and 3 should be definitely included into cons list, 4th one is already included.

And again - selling the lenses is my main inspiration for doing something new. If I have done something new I post about it.


PostPosted: Fri Nov 13, 2020 2:01 am    Post subject: Reply with quote
Thanks for the post, it is very interesting!

I wanted to ask in order to focus do you rotate the front of the lens(the lens itself) or the cylinder with the guiding pin? And is the stepdown mount part of the cylinder with the guiding pin or is it threaded and removable?

Also would less space between the helical grooves make more precise focus and do you have any specific measures between the grooves themselves when you have them made?


PostPosted: Sat Nov 14, 2020 9:20 am    Post subject: Reply with quote
I've thought of taking apart a slide projector to get at a sleeve but there is probably a lot of superfluous plastic attached to them. Most slide projector lenses already have a helicoid for this purpose.

Edit. I went and opened up a Zeiss Ikon Slide Projector I picked up in a thrift store for the lens and took one out. Only need to cut of some stuff of the back and I can attach a K-mount to it.

Projector lens sleeve by The lens profile, on Flickr


PostPosted: Sat Nov 14, 2020 3:55 pm    Post subject: Reply with quote
D1N0 wrote:
I've thought of taking apart a slide projector to get at a sleeve but there is probably a lot of superfluous plastic attached to them. Most slide projector lenses already have a helicoid for this purpose.

Edit. I went and opened up a Zeiss Ikon Slide Projector I picked up in a thrift store for the lens and took one out. Only need to cut of some stuff of the back and I can attach a K-mount to it.

Projector lens sleeve by The lens profile, on Flickr


It could work OK for some lenses but I suspect you'll need to lenses much cloer to the sensor than PK mount will allow.
My 50/1.2 projector needs to have the rear less than 10mm from the sensor for infinty focus, which IIRC places the fron't of the lens 50-60mm in fron't of the sensor. One of the mirrorless mounts on the back would work better but may still be too far out for infinity with many projector lenses.
You'll also need something to block any light getting through the opening round the focus mechanism.


PostPosted: Sat Nov 14, 2020 6:31 pm    Post subject: Reply with quote
DConvert wrote:
D1N0 wrote:
I've thought of taking apart a slide projector to get at a sleeve but there is probably a lot of superfluous plastic attached to them. Most slide projector lenses already have a helicoid for this purpose.

Edit. I went and opened up a Zeiss Ikon Slide Projector I picked up in a thrift store for the lens and took one out. Only need to cut of some stuff of the back and I can attach a K-mount to it.



It could work OK for some lenses but I suspect you'll need to lenses much cloer to the sensor than PK mount will allow.
My 50/1.2 projector needs to have the rear less than 10mm from the sensor for infinty focus, which IIRC places the fron't of the lens 50-60mm in fron't of the sensor. One of the mirrorless mounts on the back would work better but may still be too far out for infinity with many projector lenses.
You'll also need something to block any light getting through the opening round the focus mechanism.


That's OK I am not really going to do infinity anyway, and most projector lenses are bit longer than 50mm anyway so they should be ok. I'll find out.


PostPosted: Sat Nov 14, 2020 7:34 pm    Post subject: Reply with quote
D1N0 wrote:
DConvert wrote:
D1N0 wrote:
I've thought of taking apart a slide projector to get at a sleeve but there is probably a lot of superfluous plastic attached to them. Most slide projector lenses already have a helicoid for this purpose.

Edit. I went and opened up a Zeiss Ikon Slide Projector I picked up in a thrift store for the lens and took one out. Only need to cut of some stuff of the back and I can attach a K-mount to it.



It could work OK for some lenses but I suspect you'll need to lenses much cloer to the sensor than PK mount will allow.
My 50/1.2 projector needs to have the rear less than 10mm from the sensor for infinty focus, which IIRC places the fron't of the lens 50-60mm in fron't of the sensor. One of the mirrorless mounts on the back would work better but may still be too far out for infinity with many projector lenses.
You'll also need something to block any light getting through the opening round the focus mechanism.


That's OK I am not really going to do infinity anyway, and most projector lenses are bit longer than 50mm anyway so they should be ok. I'll find out.


I think my projector lenses all sit quite close to the sensor for infinity - if you're planning on using longer lenses for close up shots thats probably not to much of an issue, but it could still be an issue for portraints with a lens around 100mm. Several of my longer projector lenses could have the lens body trimmed off at the back with out any problem - some have the rear elements recessed by around 4".

Hope it works out for you - please share your results either way Smile
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