Summary Part 2 :
So what about the alternate manufacturers to Leica M-mount lens sytems ?
There is of course Voigtländer - this company is long time not existing any longer!
The company "Cosina" in Japan have the rights on the name VOIGTLÄNDER today!
Aha that's all?

....not at least :
www.closeuphotography.com/blog/cosina-voigtlander-factory-tour
That manufacturing is a real hight class manufacturing from strongest quality control
it is "high tech manufacturing" - the quality is extreme good and extreme reliable!
Well Leica is doing the same and it is better - that is correct!
The begining with M-mount was with Voigtländer system - but short after this Zeiss decided
to manufacture also there = Zeiss made from Cosina!!!
That should us tell enough about quality ! For Zeiss it is good enough - YES

!
IS THERE A DIFFERENCE IN QUALITY BETWEEN VOIGTLÄNDER MADE BY COSINA
AND ZEISS MADE BY COSINA .......
NO !!
!
So you can buy lenses from Voigtländer brand with same characteristics (quite same quality level)
of that Zeiss lenses?
YES !
!
hmm .....does this sound interisting

??
Where is then the difference between Zeiss and Voigtländer M-mount lenses?
The difference is from pricing : Zeiss is real cheap in regard of Leica ~ the half around but it depends a bit while VOIGTLÄNDER is much more cheap priced in comparison of Zeiss!
And that here mentioned isn't possible (not at the same quality level)!!!!!
!! you are thinking now - correct?
PEOPLE IT IS FACT
!
Notice : a high tech manufacturing is not possible and able in regards of : "Let us the cheap lenses made from worste quality

!
So the " general quality characteristics of both brands in regard of raw materials design and mechanical precision is absolute the same!

Trendlands typical Fairytale Time...?

Folks if you just bought a Leica M lens at about
5700,- USD last week you are of course not able to follow here - because your mind will not
allow you today

!
So were is the difference beside the name onto a Zeiss and a Voigtländer lens?
The cheaper Voigtländer lenses have a more easy design! They are generally from less speed!
So you will not find lenses of same parameters from Zeiss and Voigtländer!
Cosina does intend this - to avoid a canibalism between this two brands!
So the typical 2.0 35mm is from Zeiss :
while the classic Voigtländer Ultron has 1,7 / 35mm !
If you don't like to see pictures of a original Leica M camera with a cheaper Voigtländer lens
pls. shut your eyes here at once

!
Damned this is a bad example (the Ultron has more speed in comparision of the Zeiss

)
But each rule has its exeption (I do not intend to refer aboud the whole Voigtländer lens portfolio in comparison to the Zeiss M-mount lens series) but in many cases the Zeiss version of the simular
Voigtländer lens have had more speed! The latest evolution let have Voigtländer lenses more special from design (regarding all Nocton lenses) and Voigtländer also have more expensive lenses within its portfolio meanwhile = more and more exeptions!
Here we regard a Zeiss Biogon (what is a very good lens design to many years) and it has that
T in addition wich indicates a special correction and better glass sort special Zeiss coating a.s.o.!
(I guess therefore Zeiss/Cosina decided to max speed 2.0 to make it not too complicate from design)
Because it is extreme hard to design a lens with absolute best characteristics with more speed and more speed and more speed (btw 2.0 can also be enough speed)!
But OK the Zeiss here is much better (and more expensive) beside less speed in comparison to the
Ultron here!
Is a lens with less speed the worse lens? Not to me - if you regard its sweetspot that difference is often minized so in general a lens from less speed can have a simular characteristic at
5,6 in comparison to the competing lens at 2.8/4.0!
But lenses with max. speed are real expensive because the lens ability to show good parameters
is going low from becomming more speed! Therefore the corection of such more and more failures
is most complicate to lenses of more and more speed! Beside general issues concerning APO
design and others!
with regards