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Comparison of five different Leitz 50mm Focotar lenses

Lens
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#1 UlfW

    Ulf W

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Posted 19 February 2021 - 09:22

Finalized: Work in progress.
Last Update:
Note: Additional information or links about this lens are welcomed and will be incorporated into the first post as time permits.

Comparison of five 50mm Focotars

For more information of the individual lenses:
https://www.ultravio...-focotar-2-f45/
https://www.ultravio...-f45-from-1952/
https://www.ultravio...-f45-from-1964/
https://www.ultravio...-f45-from-1969/
https://www.ultravio...ocotar-f45-lfe/


Spectral Transmission Graphs
UV-NIR, Focotar 50mm f/4.5
Attached Image: Screen Shot 2021-02-19 at 09.55.31.png
The transmission measurement accuracy into the end of NIR range is less good due to limitations in the light source.

UV, Focotar 50mm f/4.5
Attached Image: Screen Shot 2021-02-19 at 09.53.54.png

Edited by UlfW, 23 March 2021 - 07:27.

Ulf Wilhelmson
Curious and trying to see the invisible.

#2 Andy Perrin

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Posted 19 February 2021 - 17:21

What year is the Focotar-2 from?

#3 UlfW

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Posted 19 February 2021 - 20:48

View PostAndy Perrin, on 19 February 2021 - 17:21, said:

What year is the Focotar-2 from?
1975, as stated in the post about the lens, the first link above.

For more information of the individual lenses:
https://www.ultravio...-focotar-2-f45/

Edited by UlfW, 19 February 2021 - 20:55.

Ulf Wilhelmson
Curious and trying to see the invisible.

#4 Bernard Foot

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Posted 19 February 2021 - 22:14

Ulf - where is the serial number on the lens? I can't see it on my lens, and not in the photos of your copy either.

Edited - OK, I've found it!

Edited by Bernard Foot, 19 February 2021 - 22:21.

Bernard Foot

#5 Andrea B.

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Posted 20 February 2021 - 18:40

This is a *very* useful comparison of the Focotar 50s. Thank you, Ulf.

Now I need to go find mine and see where it fits on your charts. :smile:
Andrea G. Blum
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#6 UlfW

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Posted 20 February 2021 - 20:23

Thank you Andrea.

I am beginning to find the UV Lens Technical Data section a bit cluttered.
When working with the raw data for my entries I keep information for each lens in a separate folder and have seen the same problem for the folder I keep each lens-folder.
Remember that I already have data for many more lenses to work with, even if it is not complete.

To improve the overview I have separated the folders in sub-groups:
  • Lenses for bellows, enlargers and microscopes without any focussing mechanics.
  • Normal not extreme lenses with reasonable focus lengths and ability to focus.
  • Extreme lenses like super teles and fisheye lenses
  • Lens comparisons.
Maybe there should be another group for dedicated UV-lenses too.
Then my Fused silica DIY lenses might be there together with special lenses like the UV-Nikkor I do not have.

I think that the UV Lens Technical Data section would be easier to navigate if it got subsections like the ones I use.
Would that be difficult to implement and do you see that as an improvement too?

Edited by UlfW, 20 February 2021 - 20:24.

Ulf Wilhelmson
Curious and trying to see the invisible.

#7 Stefano

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Posted 20 February 2021 - 21:22

I don't understand the colors. What is the lens with the purple curve and that awesome transmission?

#8 Andy Perrin

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Posted 20 February 2021 - 22:46

Ulf and Andrea - HARD AGREE on the suggestion for subsections.

#9 Andrea B.

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Posted 21 February 2021 - 00:53

Let's try out the subdivisions and see how it works. I will try to get to that tomorrow.
Andrea G. Blum
Often found hanging out with flowers & bees.

#10 dabateman

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Posted 21 February 2021 - 06:55

Great comparison. From the curves the 1960s looks to be a good uv transmission year.