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Lens and Optics
Industar 61 L/D Conversion

Much like gothic tales of horror most are founded in the dark recesses of the human psyche. This true tale is the story of Franken-lens. Part human, part monster...

 

Take one of these, and one of those. Hack some body parts off, rearrange them and you get...

 

A zombie half-child lens that should never have been born. (If it really was meant to be, the Russians would have done this a long time ago.)

 

Rummage through your Jupiter-8 or Jupiter-8M cadavers for a nice body part donor. Refer to Jupiter-8 lens Dismantle to see how to dismantle one and reduce it down to this. Throw the left over remains in the knacker pile.

 

Take an I61 L/D and remove the lens block by unscrewing the three grub screws around the body as shown by Blue Arrows.

 

Unscrew the lens block from the body. Again, tossing the still warm remains away.

 

If you feel demented  you may screw the I61 lens block into the Jupiter-8 body to see how the concept works. This would be a good time to put on your lab coat and flash the lights on and off while cackling madly if you choose.

 

Just a word about the differences between a J-8 and a J-8M. The base is slightly taller on the Jupiter-8 body on the left versus the Jupiter-8M body on the right. A Jupiter-8 would be the preferred way to go if you have one as it just tall enough to overlap the outside collar of the I61 lens block. I you only have a Jupiter-8M you may need to do some extra steps if neatness is a concern.

 

I found that if I glued the aperture selector ring into the Jupiter-8M body securely it would extend enough to overlap the I61 lens block.

 

One small detail that may deter most is the fact that the aperture selector ring will need to have the internal diameter enlarged to allow the I61 lens to slip inside. If you have access to a lathe this is but an excuse to spend some enjoyable time making some metal shavings fly.

 

Using the methods in Checking Lens Working Distance. determine roughly the distance the lens block should be situated in the lens body to achieve infinity focus. Just keep screwing  in the lens block little by little until you get focus at infinity, then tape it fast.

 

Use a pair of vernier callipers to make a reference measurement.

 

Screw the lens block so that it bottoms out and make another measurement taking note of the difference. This will be the size of shim you will need to fabricate.

 

I went to the hardware store and got some sort of brass fitting and turned it on my lathe to make a shim cylinder as a Jupiter-8M body requires a pretty serious shim.

 

Some extra time to fine tune your shimming distance with other thin shims.

 

When satisfied put it all together.

 

You may find that the aperture number will not line up with the existing markings on the Jupiter-8 so I just marked a line with an indelible pen to show the selected aperture.

You are now done, go out stalking around taking pictures with your Franken-lens. So how does it perform compared to something else? Have a look at this comparison.

 

June 05, 2006