Brass Lens - Carl Zeiss Jena Protar Series V

Carl Zeiss intorduced Anastigmat series lenses in 1889. However, there were many lens manufacturers was producing lenses named "Anastigmat" or similar, Carl Zeiss changed the name for her "Anastigmat" series lenses to "Protar" avoiding confusions in 1890 and patented the design.

Carl Zeiss strictly controlled the quality  and used the best glasses to produce Protar lenses. Hence, the yield-rate was low as 11% and caused the price was very expensive.

There were many manufacturers produced "Protar" series lenses under authorisation. However, there were different appearances of different "Protar" because of different materials and different polishing skills. 

1. Carl Zeiss -- Germany
2. Bausch & Lomb -- USA
3. Ross -- UK
4. E.Krauss -- France

From 1890 to 1893, Carl Zeiss developed 7 series "Protar" with different speeds as following:-

Series I	F4.5	3 groups 5 elements
Series II	F6.3	3 groups 5 elements
Series IIa	F8	3 groups 5 elements
Series III	F7.2	2 groups 4 elements
Series IIIa	F9	2 groups 4 elements
Series IV	F12.5	2 groups 4 elements
Series V	F18	2 groups 4 elements

The size of my Carl Zeiss Protar 80mm F18 is very tiny. Its glasses even smaller than my nail of little finger. It covers 5x7" and very good image quality at centre and its grey tone gradation is very beautiful.