New 75mm Hypergon Lens

[John Layton]

I believe that the fan had an asymmetrical axis which rotated around a true (measured) axis - mitigating any "blind spot" issues.

[Greg]

I believe that the fan had an asymmetrical axis which rotated around a true (measured) axis - mitigating any "blind spot" issues.

My understanding is that the fan was rotated and used for half of the exposure, then swung out of the way for the second half of the exposure.

[rayfor]

Nice job! What do you mean for that 500$ as a final price?
Looking forward for updates

not as final price, but should be cheaper than that

[rayfor]

Also looking forward for updates... I assume for 8x10 format?

designed for 8x10, but I've not tested it yet since the edge will become very dark without Central ND

[rayfor]

Is this the same lens Jason posted in another thread a few months ago?

https://www.largeformatphotography.i...light=Hypergon

Nope, I will only provide 75mm hypergon

[rayfor]

How about a circular race ball bearing mechanism surrounding the lens? The "fan" itself (laser cut from thin aluminum and black anodized) would consist of two or three blades...wider in the middle and tapering to very thin where they intersect the edge of the race at three points. The blades would obviously need to be curved downwards towards the edges as the race itself would need to be quite low-profile, so as not to interfere with the image field.

The outside of the race could be cut with gear teeth (or a ring gear attached to the outer circumference)...which are driven by a spring wound mechanism which would be cocked and fired like a shutter. Could utilize something like a slow speed mechanism (could use an existing one?) to keep the fan speed constant. Or perhaps that outer race gear could be incorporated into such a mechanism. If you watch one of these closely in action (remove one from a copal shutter and work it around)...you might see what I'm saying. Would be great I think!

Oh...and you could also incorporate something like a self-timing mechanism for much longer exposure intervals.

Seems like you'd have enough room on the flat of that plate surrounding the lens for something like this. What do you think?

At any rate...its so very exciting to see that you are re-creating such a fascinating lens! (I want one!) Good luck!

the original mechanism was elegant but fragile, and hard to control, I'm considering make a modern central ND like the one used by Super Angulon XL.

[Mark J]

The fan spins for most of the exposure time, exposing the outside area of the film/plate. It swings out of the way at the end of the exposure to expose the center. The recommendation is for the exposure time without the fan to be 1/8 of the exposure time with the fan, but that of course depends on the reciprocity failure rate of the film/plate.

The fan-equipped Hypergon was made prior to the invention of center filters, which might be a more practical solution today.

Ah thanks - that solves the mystery !

[John Layton]

But would using a central ND filter (or any standard glass filter) cause some issues - due to its refractive properties...when placed over such a curved optic? Just guessing here, mind you!

[Greg]

But would using a central ND filter (or any standard glass filter) cause some issues - due to its refractive properties...when placed over such a curved optic? Just guessing here, mind you!

What if a central ND filter was placed between the two lenses? Maybe not enough room for a shutter, but possibly room for a thin central ND filter. Also just guessing on this end.

[ridax]

But would using a central ND filter (or any standard glass filter) cause some issues - due to its refractive properties...when placed over such a curved optic? Just guessing here, mind you!

I also doubt it would work with a 135° lens that is not retrofocus nor is made according to the Roosinov's aberrational vignetting principle (like all the Biogons, Grandagons, etc., etc.). A spherically curved filter may probably be a solution.... but certainly not a cheap one.

What if a central ND filter was placed between the two lenses? Maybe not enough room for a shutter, but possibly room for a thin central ND filter. Also just guessing on this end.

Between the lens elements, the filter just wouldn't work as a center filter.

What I would like is to have an option to put yellow/green/orange/red gel filters inside the lens. It would be good for both modifying the image tones and cutting the influence of the chromatic aberration down.