I want to share with you this rare finding, a Porst 2x converter for M42 screw mount that additionally can be a 35mm f/5.6 lens, the kit consist in one body and two exchangeable lenses, one is the 2x converter and the other is the 35mm, and a front front accessory to use in combination with the 35mm lens:
With the 2x lens looks like any other converter:
And here how it looks with the 35mm lens and the front accessory:
I'm assuming 'yes' for both questions, but does it mean there's only one f-stop at 5.6, and is it a fixed-focus lens? Anything that can do double duty with a minimum of effort in the field can be a win-win, but I have to say, I've never seen anything quite like this before.
And if it works well enough to use as a lens... then it doesn't matter what it is otherwise.
Yes, it is a fixed-focus and fixed-aperture lens, the results as 35mm lens were good but I will have to test again the 2x converter, maybe was not getting along with the Super Takumar or I did something wrong.
So far I did not see anything similar from other brands, not sure if the idea and design were original from Porst, in fact there is no much information about this one or any other like it. I saw it available on Ebay and bought it just out of curiosity.
Have you tried it with color yet? That might be it's weak point with CA or accurate color rendering, but with the B&W shots, it looks pretty good to me.
I'm not sure what one can do wrong with 2x convertors. More than anything, it seems that they're either acceptable, or flat out horrible - unless their the higher-end OEM types. The Zeiss in C/Y are great, and either the made in Hong Kong or Japan version of the Yashica 2x can be pretty good if you get lucky, plus the 1.4x Nikon's are always good. The 3rd party ones seem to be a bit of a disappointment in sharpness overall.
The results from tele-converters depends a lot on what lens is used with it -- plus, it improves significantly when stopped down. Unfortunately, a 2x converter already cuts out two f-stops, so stopping down can be a problem.
Since the 35mm "lens" portion of this item, I assume does not include a diaphragm, the results of both together would be pretty bad.
It looks to me like it was designed to be used with either the converter, the 35mm section, or both -- making a 70mm. Is that correct?
It doesn't look like it will accept both pieces at one time, so I presume it's either meant to work as a 35mm lens, or a 2x convertor
Exactly, the body only accepts one piece at the same time, either the 2x or the 35mm and once in, the piece must be locked into position as shown in the pictures with the red and green dots (red dot means unlocked, so it must be pressed a little and then rotated to match with the green dot to get into the correct position and locked).
The tests shots you see here are the only ones so far, I would like to test it with color film but I have to buy C41 chems first, as soon I test it I will post the results here.
In regards to Porst, as far as I know they did not manufacture much, rather re-branding things made by others, but so far I was not able to find any other brands manufacturing this kit, so it seems it was made or at least designed by them.