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I'm feeling an itch
#21
The vintage clash of the 105mm f/2.5 is coming.

Besides the Minolta MC Rokkor 105mm f/2.5 I also got a Nikkor-P 105mm f/2.5.

Maybe I'll also go for an Olympus OM 100mm f/2.8.

And then destroy them all with a Voigtlander APO Lanthar 110mm f/2.5 .... LOL. (or maybe the Sigma 90mm f/2.8 in a more fair competition)
Chief Editor - opticallimits.com

Doing all things Canon, MFT, Sony and Fuji
#22
(04-25-2022, 01:18 PM)Klaus Wrote: I'm currently discovering the wonderful world of radioactive lenses LOL

https://www.robertallenkautzphoto.com/radioactivelenses

Radioactive lenses tend to develop yellow tint with aging, so I don't know how reliable  the finding would be 


Your link states that putting the lenses in the sun should clear this issue but I am not sure about it 

[Image: Yellowing_of_thorium_lenses.jpg]
#23
It is widely known that lenses with thorium glass do yellow when not used, and that exposing them to sunlight (UV) gets rid of the yellowing again. The yellowing can be countered by custom white balance anyway, and should not impact digital photography much.
What I have no read about is what actually yellows, and from which kind of radiation, and how UV light radiation counters/reverses that.
#24
Yes, UV light seems to work. Some are pointing to a specific Ikea UV lamp for fixing the yellow cast. ;-)

FWIW, I found this here:

Over extended time periods, thoriated glass may develop significant discoloration. This is due to induced F-centers forming in the glass as the radioactive decay of the thorium progresses. The formation of F-centers is due to the ionizing effect of the high energy thorium decay products. This process can potentially be reversed by annealing the glass or exposing it to light.

Ref.: https://en.wikipedia.org/wiki/Thoriated_glass
Chief Editor - opticallimits.com

Doing all things Canon, MFT, Sony and Fuji
#25
Cool Klaus, neat explanation of what occurs there.

"An F center or Farbe center (from the original German Farbzentrum, where Farbe means color and zentrum means center) is a type of crystallographic defect in which an anionic vacancy in a crystal lattice is occupied by one or more unpaired electrons. Electrons in such a vacancy in a crystal lattice tend to absorb light in the visible spectrum such that a material that is usually transparent becomes colored. The greater the number of F centers, the more intense the color of the compound. F centers are a type of color center."

https://en.wikipedia.org/wiki/F-center
#26
So the first of the 100's came in today - the Minolta MC Rokkor 100mm f/2.5.

It is downright depressing to experience the build quality of these old babies - today's lenses feel like cheap crap in comparison.
Chief Editor - opticallimits.com

Doing all things Canon, MFT, Sony and Fuji
#27
I'm reading this thread now... i made some shots with an helios 44k-4 mc, 44m-4 mc and a zeiss biotar 58mm f2 m42.

the latter was mine and unfortunatly has fallen into a river Sad .

i used helios on aps fuji, they are rather sharp @ f.56-8, ugly (UGLY i mean) borders and corners @ f2, but anyway not bad for portraits. bokeh seemed the same between zeiss and helios, full wide (zeiss had 12 blades, helios 6).

i have a shot for comparison between f2 and f8, i think with the k, here: https://we.tl/t-cKl2mpMFLd

full image, center crop, till extreme crop. i noticed also a strong colour cast with iris blades closed.

i think you'll have fun!
#28
Regarding the crazy amount of vintage lenses, it'll not be more than a tiny snapshot but yes, it'll be something different in a sea of modern high-performance lenses.

And it'll be fun to destroy some "legends" ... LOL

The thing that I'm most baffled about is the pricing of some of these vintage lenses. I understand that some are valuable to collectors and some are interesting to the video folks.
However, e.g. the whole 85mm league from the main manufacturers has bizarre price tags. Others are dirt cheap for no specific reason either it seems.
Chief Editor - opticallimits.com

Doing all things Canon, MFT, Sony and Fuji
#29
Oh well, according to the tracking the Helis 44 is now ... in Kyiv ...
It was sent from Zaporizhia in early May ... which is now in the war zone.

Even if it never arrives here - I hope the little business helped the seller a bit
Chief Editor - opticallimits.com

Doing all things Canon, MFT, Sony and Fuji
#30
(05-14-2022, 08:22 AM)Klaus Wrote: Oh well, according to the tracking the Helis 44 is now ... in Kyiv ...
It was sent from Zaporizhia in early May ... which is now in the war zone.

Even if it never arrives here - I hope the little business helped the seller a bit

As someone who has effectively been as a child several times in war zones, and who has lived as a refugee I know how bad things should be there, when the only thing that matters is staying alive and not seeing your loved ones killed.

I remember in 1990 after our house was burnt into ashes, I was 12 years old, and as soon as we could get there I rushed into my room to check on my photographs, I could see the photos between the ashes, but as soon as I tried to grab one it disintegrated onto a grey powder .... I never took another photo again till 2004 when I restarted photography.

Hope this madness ends soon
  


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