Minolta Chiyoko 5cm F2- Took one Apart

Sonnar Brian

Sonnar Brian

Product of the Fifties
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I've seen this lens listed as 7 elements in 4 groups, like a Summitar AND I've seen this lens listed as 7 elements in 6 groups. The early version of the lens takes 40.5mm filters, the later takes 43mm filters. I have a perfect condition late one, no need to take apart. Found a very early one on Ebay with internal haze- got it cheap. Good reason to take it apart and satisfy curiosity.





Barrel held into focus mount via a retaining ring.



 
Big Thick Shim.



Rear fixture held in with retaining ring.



Have a suction cup handy, and be prepared to gently pry out.
 


Putting the glass back to the fixture- it separated into two elements with a very thin spacer. Some "concoction" on the spacer to hold the elements together. The front element is very thin- if you do this, get the thicker element into the tight fixture and make sure it is all the way in, check the rim of the glass to be even across the rim. Spacer in- and make sure the front element is perfectly lined up before screwing the retaining ring back in. It will crack if misaligned.

Lens Groups are defined as being cemented, air-spaced, and oil-spaced. The Minolta Chiyoko 5cm F2 is a 2-2-2-1: 7 element in 4 groups. The 1st and 2nd doublet are air-spaced groups, the doublet behind the aperture is cemented. Air-spaced doublets allow 4 radii to be used for better control of spherical aberration. As this lens was always coated, the designers apparently felt the extra degree of freedom was worth the extra air/glass interfaces. A second reason to use air-spaced (and oil spaced) groups is to accommodate different coefficients of expansion of glass elements used in the group.
 
Most of the haze came out- the surface behind the aperture had some slight residual coating damage, but out of the way of the optical path.





Wide-Open, swirly Bokeh like a Summitar.

Flare torture test-



This lens passes.

Focus test, and away from direct Sun.


Wide-Open, and

at F4.



All of the Minolta Chiyoko lenses are good. Prices have dropped in the last few years. The 45 F2.8, 50 F2.8, and 85/2.8 are 3-1-1: 5 elements in 3 groups. The 11cm F5.6 is tiny 4 element in 2 group, but close-focus is not so great. The 135/4 is a 4 element in 3 group 2-1-1. Probably the front triplet of the shorter lenses collapsed into a doublet. The rare 3.5cm F3.5 is a Tessar, and is the first multi-coated lens making its appearance in 1956. The one that I have has better contrast and flare resistance than my Nikkor 3.5cm F3.5.
 
I own the 5cm F2.8: It is not a Tessar. It is a 5 element in 3 group, 3-1-1. It is the same optical formula as the 45/2.8. The latter- is tiny, and uses 34mm filters. The 50/2.8 uses 40.5mm filters. I have both- but end up shooting the 45/2.8 more than the 50/2.8.

Minolta_Chiyoko_Collection by fiftyonepointsix, on Flickr

My Minolta lens collection, missing the early 5cm F2-
 
This one came on a working Minolta II, lens and camera were a great price.

I have a difficult selling lenses- especially ones that are so unique in design. My wife told me "If you like it, keep it. If you use it, keep it. If you do not like it and you do not use it- sell it".
How I got 120 lenses in Leica Mount.
 
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