Combining Front and Fear Optical Groups From Different Scopes

[Caleb Genheimer]

Here’s a Frankensteined scope that works out to 1.33X squeeze. I’m actually able to go as wide as 17mm on M4/3:

Alright, so I have seen some other people doing this with success and wanted to start a topic on it. Basically what I’ve found is that you can combine a front from one scope with the rear of another, and some combinations will be sharp, others will not be compatible. Regardless, the compatible setups will only be sharp when set to infinity, and the distance between the two groups determines both focus and compression ratio. 

Once again, it is important to note the infinity-only nature of doing this. You cannot close focus a mismatched pair of anamorphic groups. However, focusing via front diopters or variable diopters is still fair game.

This means that, assuming the same front group, a rear group that hits infinity with the groups close to each other will have a mild compression, whereas a different rear group might hit infinity when further from the front group, which yields a stronger compression ratio. 

With the front and rear the same distance apart as in the original front scope, the compression is the same as the original (usually 2X), but in that case, you may as well use the scope with its original rear group as that’s its intended specification. 

The other changing factor is maximum useable angle of view. It really is exactly like looking through a tube or tunnel. A front with a certain diameter supports wider angle of view if it is closer to the rear group, and the useable angle of view decreases as the groupings get farther apart. This creates an inverse relationship between wide angle of view and compression ratio (assuming the “constant” is the front group and the “variable” is various rear groups.) 

This means that long scopes which have limited angle of view in their stock configuration can be modified with new rear optical groups to increase their angle of view, at a cost of compression ratio. Basically, you can turn a 2X scope into a wider 1.5X or 1.33X scope. 

I’m still a 2X fanboy, but the limitation is usually wide angle compatibility. A great 1.33X that truly goes wide could allow me to have a wide angle in my anamorphic arsenal. It may be deceiving, but for reference, the +2 diopter in my example video puts the focus at around 12 inches. That’s how close I was to the subject matter, and I was still wide enough to capture a full human face. That’s pretty crazy for any anamorphic!

I’ve only disassembled four scopes so far, but I have more on the way to further my testing. I have some more theories, but feel that I need to test more before I can be certain that my theories are accurate. 

Theory 1: Some rear groups just seem to play nice, and others just seem to not work. I’m not sure why at this point, and I’m no optics expert, but one rear group that I have seems to work with all the front groups, another is ok stopped down, and yet another is garbage out towards the edges.

Theory 2: The distance between the front and rear groups may correlate (but not replicate) to the length of the scope that the rear group is sourced from. This may eventually aid in predicting the squeeze ratio and angle of view of a combination of scopes, where the front group has already been tested. For example, if a front/rear combo hits 1.33X, but I want to achieve 1.5X, I should source a new rear from a scope that is slightly longer than the scope that the 1.33X originally sourced its rear from. Again, more testing needed.

Theory 3: You can’t use closeup diopter elements or variable diopters in between the front and rear groups to simply bring them closer and reduce vignetting/squeeze. It partially works in center frame, but introduces nasty distorted blur everywhere else. Naturally, I’m no expert, but it was something I was curious about, so I tried it.

Has anyone else had good luck with combining scope elements? I’d like to discuss it a bit and see what others experiences are.

[leslie]

that's some novel thinking there. Which scopes have you pulled apart ? i have a set of nap 35 2-3 pulled apart for curiosities sake. Thats about as far as i got. Your ideas might inspire me to experiment a little further. what really intrigues me is the front mounted variable focus solutions. what are they exactly ?and how do they work ? and why haven't the chinese copied one and mass produced it lots cheaper like everything else ? but i digress.

[Caleb Genheimer]

The front variable diopters are just a positive and negative element with a helicoil as far as I know. The issue with kitbashing one from off the shelf diopters and/or producing one on the cheap is similar to the issues with doing things like speed boosters/focal reducers on the cheap. It’s a recipe for bad chromatic aberration if all elements in the design aren’t optimized and  well coated. The FVD-16A and recent FVD-35A are examples of more mass-produced options (versus Rectilux super small batch)... and I’d say SLR Magic’s Rangefinder is about as cheaply as you’d make one and still have it work decently.

 

Even the FVD-35A is a steal at $1K when you consider that the rear element is 95mm diameter, and the front is even bigger. Good diopters that size aren’t cheap to begin with.

Incidently, I was hoping the NAP-3 would prove useful, as they’re cheap as dirt and available everywhere, but they’re the optics that rendered the aforementioned poor results. I have a couple B&L scopes that work nice (but balsam separation inevitably claims those for the grave), a Meopta Anagon, and obviously the NAP. 

I might try separating the B&L scope optics and re-cementing them with modern adhesive for some additional experimentation. 

[Caleb Genheimer]

It really seems like pairing groups from two scopes of a similar physical size is pretty much a wash. I suspect that the scope I am utilizing for a front (B&L) may even be for 70mm projection as it is a monster... and the rears therefore I’ve been pairing with it are for regular 35mm projection. I have a cheap 16mm projection B&L on the way to test this theory, and see if I get similar results pairing it with a 35mm projection scope.

[Caleb Genheimer]

Here’s the B&L front, Meopta rear. A bit of a quicker looser test, but it was easy to see that it resolves really well, even out into the corners. It ends up at 1.5X, and this is with a Tamron SP 24mm all at f2.8. Again, the 95mm +1 diopter vignettes when it is in front, so if I want to use this B&L seriously, I would need to get something like a 114mm diopter.

Seems like the primary (source locked) flares in anamorphic lenses come from the rear element, as that’s the straw gold flare from the Meopta. The B&L flares blue, so that’s also still there from the front group. I think actually really like the contrasting flares:

I’m at the point now where I’m waiting until next week when a couple more lenses arrive to disassemble. Got a 16mm B&L that looks to be of similar era (silver) to the ones I already have, and a big ‘ol Möller 63/2X.

If anyone has lenses with only one good element, or other frustrating damage, I’d consider giving you a little cash for them depending on the condition... or just big unwieldy scopes that you don’t use. The only scopes I’ve ruled out are the Russian NAP stuff. They don’t play nice with others. 

I’m going to do my best to analyze all my results and share them here for everyone, so any help or insights would be very welcome.

I think the most exciting aspect of it to me is the potential to not only come up with attractively specced unique scopes, but to also breathe life and a second chance into otherwise bulky/impractical lenses. The B&L in original form is bigger than my head! 

[leslie]

careful you might start a whole new craze,  the double flares are interesting 

[Rikoshet]

On 8/8/2019 at 4:59 AM, Caleb Genheimer said:

Here’s the B&L front, Meopta rear. A bit of a quicker looser test, but it was easy to see that it resolves really well, even out into the corners. It ends up at 1.5X, and this is with a Tamron SP 24mm all at f2.8. Again, the 95mm +1 diopter vignettes when it is in front, so if I want to use this B&L seriously, I would need to get something like a 114mm diopter.

Seems like the primary (source locked) flares in anamorphic lenses come from the rear element, as that’s the straw gold flare from the Meopta. The B&L flares blue, so that’s also still there from the front group. I think actually really like the contrasting flares:

I’m at the point now where I’m waiting until next week when a couple more lenses arrive to disassemble. Got a 16mm B&L that looks to be of similar era (silver) to the ones I already have, and a big ‘ol Möller 63/2X.

If anyone has lenses with only one good element, or other frustrating damage, I’d consider giving you a little cash for them depending on the condition... or just big unwieldy scopes that you don’t use. The only scopes I’ve ruled out are the Russian NAP stuff. They don’t play nice with others. 

I’m going to do my best to analyze all my results and share them here for everyone, so any help or insights would be very welcome.

I think the most exciting aspect of it to me is the potential to not only come up with attractively specced unique scopes, but to also breathe life and a second chance into otherwise bulky/impractical lenses. The B&L in original form is bigger than my head! 

I like the idea to make shorter scopes and also love the double golden/blue flares!!!

[Caleb Genheimer]

Yeah! Although they’re shorter than original... not necessarily smaller or lighter:

[ken]

I did some research several years ago.  And got these combination:

1.5X:                          Sphere/Cylinder
Schneider ES front     0/-10.50
ISCO integrated rear  +7.75/-7.75

1.3X:
Moller46/2x front      0/-9 to -10 (estimated value, due to too thick, unable to measure)
ISCO integrated rear   +7.75/-7.75

The combination means using 2X lens with more powerful rear lens(or weaker front lens) can get less ratio than 2X.
For reference, original combination is:

2X:
Schneider ES front     0/-10.50
Schneider ES rear      +6.00/-6.00

2X:
ISCO integrated front  0/-13.75?
ISCO integrated rear   +7.75/-7.75

BTW, for 16H,
2X:
16H front              0/-17.00
16H rear               +9.50/-9.50

So that explain powerful lens combination(shorter distance between front and rear lenses) has wider angle.

[Caleb Genheimer]

Gotcha! 

I have no actual optics experience, nor any way to measure the optical power of the lenses, so it is nice to have quantified confirmation of what I was hypothesizing.

This means that it is important to start with a reasonably wide-shooting anamorphic for the front optic, and add a rear from a shorter scope to reduce to the desired squeeze ratio and achieve an increase in taking lens angle of view. 

I’m *almost* tempted to snag the rear group out of my 16-H to see if I can’t make a killer wide 1.5X or even 1.33X.

Again, I now have a bunch of bigger 35mm projection scopes, many almost the same size, so armed with this knowledge, the best path to good results is probably using those fronts with 16mm anamorphic rear elements. They’ll be way smaller than the fronts, but it is probably where some of the rarer anamorphics get their design from, like the Möller 30. 

I suppose 16mm fronts with 8mm/Baby rears is not entirely out of the question either.