https://www.ebay.com/itm/154220055064
Will this Pentax 67 Helicoid Extension Tube be useful to mount a projector lens? I have seen a few projector lenses being mounted on a Pentax 67 and I would like to do the same. I'm looking for an easy mounting solution and have zero experience in 3D printing or CNC machining stuff. I found this exact version of helicoid locally but I've never done this before so I hoping to get some help before I purchase it. Thanks!
Sold to u/wowbobwow
Jupiter 9 silver version, made in 1961 - contax Kiev rangefinder mount.
Glass is in excellent condition. slight dust in the lens. Aperture ring works perfectly, opens up a 15 bladed aperture - slight oil on the blades but works perfectly well. Focus ring works (but not as smooth as my takumar lenses, especially at the near focus range. It makes images with beautiful Bokeh.
Industar 26n 50mm 2.8 in contax kiev rangefinder mount. Lens is in okay condition - has oil on aperture blades but works.
Custom made contax-kiev to Sony E mount adapter. Bought from eBay along with the industar lens above. This adapter has the in built focus helicoid for smaller primes that didn't have a focus ring on the lens (including contax rf Zeiss lenses)
All three items sold together for $125 - PayPal G&S and Shipping to CONUS included in the price. Priced low to move fast.
Sample pictures shot on Sony A7 and the Jupiter 9, unedited jpegs straight out of the camera, on April 14th 2020. Most images were shot wide open - very few were stopped down to f2.8 I don't remember if any of these were stopped down. The lens had wonderful flaring that I had used creatively for some portraits - never had a lens hood for it, using my hand to shade if necessary. May have used it once in July again but don't have pictures I can share from that day
helicoid: curved, like the spire of a univalve shell
See tree for helicoid: https://treegledictionary.org/define/helicoid
I’m trying to find a bit more information on the Pentax 67 Helicoid Extension tube. I could really use something that has a variable extension to save carrying around multiple tubes. This one can be extended between 32.2mm and 52mm and looks pretty solid. If anyone has used it, would you recommend this or individual tubes? Do I have to have the lens set to manual/stop it down myself before exposure?
It’s a shame that Pentax didn’t put any exposure comp info on the tube itself, but I’m expecting between .05 - 1 stop of difference in exposure if I was using it. All in all it seems worthwhile, but at £100 for a small chunk of metal I need to see some results or hear from folk and I can’t find anything!
A new type of metallo‐polymer with helicoidal structure was constructed through the combination of covalent polymerization and intramolecular coordination‐driven self‐assembly. Owing to the positive charges on the inner rim of helicoid, double‐stranded DNA molecules (dsDNA) could interact with metallo‐helicoid (H) via electrostatic interactions. Notably, dsDNA allowed exclusive formation of H with right handedness by means of chiral induction.
Abstract
In this study, we established a feasible strategy to construct a new type of metallo‐polymer with helicoidal structure through the combination of covalent polymerization and intramolecular coordination‐driven self‐assembly. In the design, a tetratopic monomer (M) was prepared with two terminal alkynes in the outer rim for polymerization, and two terpyridines (TPYs) in the inner rim for subsequent folding by selective intramolecular coordination. Then, the linear covalent polymer (P) was synthesized by polymerization of M via Glaser‐Hay homocoupling reaction. Finally, intramolecular coordination interactions between TPYs and Zn(II) folded the backbone of P into a right‐ or left‐handed metallo‐helicoid (H) with double rims. Owing to multiple positive charges on the inner rim of helicoid, double‐stranded DNA molecules (dsDNA) could interact with H through electrostatic interactions. Remarkably, dsDNA allowed exclusive formation of H with right handedness by means of chiral induction.
https://ift.tt/34ncTeQ
I’m trying to find a bit more information on the Pentax 67 Helicoid Extension tube. I could really use something that has a variable extension to save carrying around multiple tubes. This one can be extended between 32.2mm and 52mm and looks pretty solid. If anyone has used it, would you recommend this or individual tubes? Do I have to have the lens set to manual/stop it down myself before exposure?
It’s a shame that Pentax didn’t put any exposure comp info on the tube itself, but I’m expecting between .05 - 1 stop of difference in exposure if I was using it. All in all it seems worthwhile, but at £100 for a small chunk of metal I need to see some results or hear from folk and I can’t find anything!
helicoid: curved, like the spire of a univalve shell
See tree for helicoid: https://treegledictionary.org/define/helicoid
In this study, we established a feasible strategy to construct a new type of metallo‐polymer with helicoid‐like structure through the combination of covalent polymerization and intramolecular coordination‐driven self‐assembly. In the design, a tetratopic monomer ( M ) was prepared with two terminal alkynes in the outer rim for polymerization, and two terminal terpyridines (TPYs) in the inner rim for subsequent folding by selective intramolecular coordination. Then, the linear covalent polymer ( P ) was synthesized by polymerization of M through Hay‐Glaser homocoupling reaction. Finally, intramolecular coordination interactions between TPYs and Zn(II) folded the backbone of P into a right‐ or left‐handed metallo‐helicoid ( H ) with double rims. Due to multiple positive charges on the inner rim of helicoid, double‐stranded DNA molecules (dsDNA) could interact with H via electrostatic interactions. Remarkably, dsDNA allowed exclusive formation of H with right handedness by means of chiral induction. Furthermore, the interaction with DNA molecules led to the enhancement of luminescent efficiency of H through restricted intramolecular motions. The processes of encapsulation of DNA molecules were able to be probed by time‐dependent fluorescent spectroscopy. Our study not only broadened the scope of metallo‐ polymer, but also paved a new avenue for the development of host‐guest systems and emissive materials.
https://ift.tt/34ncTeQ
