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Perhaps a silly question?
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PostPosted: Sun Sep 02, 2012 5:08 pm    Post subject: Perhaps a silly question? Reply with quote
Below is a picture of the lens block from a busted Nizo cine camera. The lens is Schneider 1.4/7-56mm Macro for Super 8mm format.

The gap between the front and rear elements is for the prism and shutter. I was wondering if I could hook up the front end of this lens to the rear of say a Helios 44-2 or something similar in the cheap category Smile. If possible it would give a nice 2.0/7-56mm.

What do you think?



PostPosted: Sun Sep 02, 2012 5:18 pm    Post subject: Reply with quote
I think those rear elements are needed, I tried one of these lenses after removing it from a Nizo and it wouldn't form an image, just blurs of light.

I think if you add any elements it will not work either.

Being for a super 8 camera, this lens might not cover even a M4/3 sensor so I'm not sure it's worth much effort, sadly.



PostPosted: Sun Sep 02, 2012 5:44 pm    Post subject: Reply with quote
The fixed rear elements are most definitely needed, since the front end will not form an image, and they are responsible for the size of the image circle and for correct focus at registration distance.

My thought is that they can be replaced with larger elements for a larger image circle and also for larger registration distance and I was thinking of the rear elements of for example the Helios 44-2 as a suitable candidate.


PostPosted: Sun Sep 02, 2012 6:01 pm    Post subject: Reply with quote
You are trying some retrofocus construction? Interesting!

http://en.wikipedia.org/wiki/Ang%C3%A9nieux_retrofocus


PostPosted: Sun Sep 02, 2012 6:46 pm    Post subject: Reply with quote
Hmmm, not quite.

My thought is to remove the front gauss group from a Helios 44-2 and replace it with the Schneider front end at the correct distance from the aperture blades, the Helios would be set to inf and focus locked from moving. The focussing and zoom is performed in the Schneider.

The inverted gauss group in the Helios should expand the image to 35mm format at M42 registration - maybe because I dont know for sure Smile

Some people call this type of mod Frankesteining a lens LOL


PostPosted: Sun Sep 02, 2012 8:50 pm    Post subject: Reply with quote
I'm confused, but fascinated. Go ahead, I want to see the results. Wink


PostPosted: Mon Sep 03, 2012 2:12 am    Post subject: Reply with quote
in 10 steps

1. get a pair of calipers
2. measure the distance between the rear group and the front.
3. get a unused body cap for your camera
4. cut a hole in said body cap about the size of the rear group, insert rear group into new home
5. cut some pvc pipe the side of the gap you measured earlier
6. paint the inside of the pvc pipe matt black
7. glue pipe to body cap
8. use electrical tape to attach front of lens
9. test
10. adjust, retest, repeat.

you now have frankenlens.


PostPosted: Mon Sep 03, 2012 5:38 am    Post subject: Reply with quote
Yeah the only way a non optical tech would know for sure is to kludge it together and see the results, good luck.


PostPosted: Mon Sep 03, 2012 1:28 pm    Post subject: Reply with quote
@enliten

I disagree, a Frankenlens (good name), must use parts from dead lenses Smile :LOL


PostPosted: Mon Sep 03, 2012 1:41 pm    Post subject: Reply with quote
I did some research on the Variogon and found this lens scheme



Showing the front cell has nine elements and the rear cell has five elements - all the focus and zoom happens in the front cell.

I have disassembled the block into front and rear cells seen below



PostPosted: Mon Sep 03, 2012 1:57 pm    Post subject: Reply with quote
Next I held the front cell against the front of a Helios set at INF and got this image



Things to note are that the front cell of the Helios is reacting with the Variogon to give soft focus and the vignetting.

I am hoping that when I find a broken Helios to take apart I can remove its front cell and put the Variogon much nearer to the Iris plane, which hopefully will solve these two issues.

It also is pleasing that the Variogon will fit inside the Helios body, no plastic tubes required Smile
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