Steinheil München 50mm f/2.8 Cassar S

[ulf]

Finalized: Work in progress.

Last Update:

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Steinheil München 50mm f/2.8 Cassar S

 

Manufacturer: Steinheil München

Manufacturer's lens designation: Steinheil München Cassar S 1:2.8 f=50mm

Currently manufactured: No

Lens type: Manual focus, Prime, Normal

Focal length: 50mm

Aperture range: f/2.8 – f/16, Manual, 10 blades, no click stops

Design: 3 elements in 3 groups

Flange Focus distance: Mount dependable

Mount: M42 x 1.0**, EXA, Also as a fixed mounted lens on several cameras

Sensor format/coverage: up to 24mm x 36mm

Front filter: 40.5 mm x 0.75 mm

Introduction year: early 1950?

S/N of test object: 2020691

**Mount of test object

 

Lens review (VIS), on the web:

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Image of test object:

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Transmittance Summary

Definitions of the parameters below

• Range: The Cassar S 1:2.8 f=50mm lens transmits 0-74% in an increasing slope from 309nm to 400nm.
  
• T_VISmax (%) = 90%
  
• T_400nm (%) = 74%
  
• T_365nm (%) = 68%
  This moderate to high percentage is an indicator for a short exposure time under typical UV-pass filtration peaking around 365 nm.
  
• λ_{UV HMvis}(nm) = 337nm
  
• λ_{UV HM400} (nm) = 331nm
  
• λ_{UV Zero} (nm) = 309nm
  These three values indicate that the lens is working well for UV-B photography with some filters and a few for this, suitable cameras.
  

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Spectral transmission graphs:

UV-NIR, Cassar S 1:2.8 f=50mm

The transmission measurement accuracy into the end of NIR range is less good due to limitations in the light source.

 

UV, Cassar S 1:2.8 f=50mm

UV-Log, Cassar S 1:2.8 f=50mm

Numerical Spectra Data available: Pending

 

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Filters and how to use them on this lens:

The front filter thread is 40.5mm standard filter thread. A step-up filter ring might be needed.

 

It is also possible to use rear mounted filters, either in lens mount adapters for mirrorless cameras like Sony A-series etc, or placed directly in the camera.

 

An alternative, if space in the camera allows, is to putty-mount a filter directly against the lenses rear flat parts.

The rear lens element is recessed and thus safe and the ring provides a good reference plane for orienting the filter normal to the optic axis.

 

My Omega 330W80 Improved Ø25mm, is mounted in a 27mm-filter ring and would work well to mount as it is.

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Handling and focussing:

This lens has a focusing helicoid that smoothly turns almost a full turn for focus at infinity to around 1m.

To focus closer external bellows, focusing helicoids or extension rings are needed.

Then image quality might improve by reverse mounting the lens.

 

Flare and sun-stars:

TBD

 

Sharpness:

The lens has a rather curved focus plane and on a full frame sensor the corners are quite soft even when stopped down.

 

Lens distortion:

TBD

 

Chromatic Aberration / fringing in UV:

TBD

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Image samples:

[OlDoinyo]

Another version of this lens has a smaller front barrel with no filter threads.

[Fandyus]

I've recently been wondering if perhaps other triplets should be tested this way. There are plenty and their image quality is comparable. I've been thinking of getting the Meyer Optik Görlitz Domiplan 50mm f/2.8 to see how well it performs.

[Avalon]

So it's the best transmission non UV dedicated lens?

[ulf]

26 minutes ago, Avalon said:

So it's the best transmission non UV dedicated lens?

This topic is about Steinheil München Cassar S 1:2.8 f=50mm!

Please do NOT litter it with general questions. Instead start a new topic with a clear question. 

The forum is for discussions, but this technical section is intended to be more formal.