[Simen1]

Does it exist a 67 lens to K mount camera speed booster?

If not, what does it take to make one? Where can I find the optics? Can astronomy telescope shops provide focal reducers with large enough image circle and good IQ?

The mechanics is easier. It should be easy to find a 67 lens to K camera adapter that can donate the two flanges to this project. Then I just need to calculate distances and make a metal barrel to mount the flanges and the optics.

[RuiC]

Does it exist a 67 lens to K mount camera speed booster?

If not, what does it take to make one? Where can I find the optics? Can astronomy telescope shops provide focal reducers with large enough image circle and good IQ?

The mechanics is easier. It should be easy to find a 67 lens to K camera adapter that can donate the two flanges to this project. Then I just need to calculate distances and make a metal barrel to mount the flanges and the optics.

Hi! What do you mean by a "speed booster" ?

[UncleVanya]

I suspect the level of precision and the specifics of coatings may be an issue that takes a lot more to overcome than expected.

[Fogel70]

I suspect the market for this adapter is too small. It would need a new unique optical formula never used before I believe.

[desertscape]

Shortening the focal length of the lens can be done, just as lengthening can be done ( AKA a 1.4x or 2x converter). Shortening of the focal length will increase your speed. Using a positive achromat behind the lens is a start but maybe a bent Cooke triplet would work better. The adapter would have to be shortened so the image would reach the focal plane in focus.

[Simen1]

Hi! What do you mean by a "speed booster" ?

A focal length reducer. The opposite of a tele converter. Here are some examples of speed boosters for other lens and camera systems.

In example one can use a 0.5x reducer to reduce a 100mm f/2 lens to effectively 50mm f/1 (if the flange distances are compatible)

[Digitalis]

Does it exist a 67 lens to K mount camera speed booster?

NO.

what does it take to make one?

At least a Masters in optical design and engineering, access to optical production facilities and optical multi coating facilities, you can't just buy an optical element or two off the shelf, there are hundreds of variables in optical design that need to be calculated and designed into an optic such as this.

Can astronomy telescope shops provide focal reducers with large enough image circle and good IQ?

NO.

use a 0.5x reducer to reduce a 100mm f/2 lens to effectively 50mm f/1

For all the time and tedious tinkering you would be better off buying a Leica and a Noctilux. I own three of the Noctilux (noctili?) lenses Leica has made and to be honest, f/1 is an aperture I only use when I absolutely have no other choice, as have many other photographers who have worked with such lenses have concluded.. Bokeh from the Noctilux (even the current 50mm f/0.95 ASPH) is either gorgeous, or so ugly you'll want gouge your eyes out with a spork....and question why you spent so much on a lens.

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Last edited by Digitalis; 11-17-2015 at 06:54 AM.

[wombat2go]

with a spork....

Crikey, Digit,
I haven't seen one of those since 1966
But a true Aussie would rather use a Splayd.
https://en.wikipedia.org/wiki/Splayd

[Digitalis]

But a true Aussie would rather use a Splayd.

My family uses those to eat desserts..

[hsteeves]

My family uses those to eat desserts..

so, would a Splayd be a combination of a spoon and a spade? I always knew Aussies had big mouths but ...

[desertscape]

Simen1-- If you are intent on pursuing this further, I would suggest using the rear half of a view camera Plasmat lens. It consists of a positive element followed by a negative and another positive element. There is no guarantee that you will end up with a flat field though. Screw in Achromats are sometimes used in front of lenses for macro work. One of these may work behind the lens as well, for your purposes.

[Digitalis]

Screw in Achromats are sometimes used in front of lenses for macro work

Apochromats are superior, if the prime lens isn't properly colour corrected, adding a rear cell from a plasmat will in all probability cause horrendous Longditudinal chromatic aberration. Plasmats are very old lens designs, they almost pre-date WWI. The most common variants are suited to 8½ × 6½ format - what was known as the "full plate" tintype, putting one on a modern APS-C dslr might be pushing it.

[desertscape]

I would not suggest using an old Plasmat but a modern one. There have been lots of improvements to that design with the advent of exotic glass. There are several APO designated Plasmats out there from Rodenstock, Schneider etc.

[Digitalis]

here are several APO designated Plasmats out there from Rodenstock, Schneider etc.

If bought new, such a thing will cost quite a bit, especially if it is from Schneider.

[Paul Ewins]

There are quite a few modestly priced APO plasmats out there and it might be possible to find one with a faulty shutter or damaged from element for a few hundred dollars. Having said that, it is going to be pot luck whether it is useful. The typical focal lengths will be 150, 180 or 210mm. However half a plasmat is still a complete lens in its own right, typically with a focal length around 1.7 or 1.8x of the complete lens, so you are looking at focal lengths of 200 - 400mm. The other downside is that half of a plasmat is less corrected than a whole plasmat which probably wipes out the advantage of looking for a more modern APO version.