What is an Unar?

[Shangheye]

I have been offered a brass B&L Unar lens (not portrait) and I was wondering if anyone can help me understand what to expect. The lens is labeled f1.5, but apparently this is based on an old designation...what would be the new f number? Also, I have been told the focal length is somewhere between 160mm and 180mm (nothing written on the barrel)...Does anyone know if they came in particular focal lengths?

Are these lenses any good?

I did a search, and though Unar does turn up, it seems to be basically about the portrait (soft focus) version of this lens. I don't want a soft focus lens, and I assume this version is normal.

If I do buy it, it will be for use with my series D Graflex....Does anyone know if it would allow me to infinity focus?

Thanks for any advice.

rgds, Kal

 

[Ole]

A portrait lens is not necessarily soft focus, and at the time when the Zeiss Unar was made it often meant a lens that was fast enough to take a portrait without needing a tea-break in mid exposure. The Portrait Unar had a diffusing attachment - a "soft filter".

B&L licensed the Zeiss line, and made them in their own set of focal lengths and with the US aperture scale.

Where the f-stop scale runs 4, 5.6, 8, 11, 16, 22, 32; the corresponding US scale is 1, 2, 4, 8, 16, 32, 64 with 16 being the same in both scales. That means the 1.5 Unar is about f:4.5.

 

[Denis K]

Kingslake claims that the Unar was an improvement to Rudolph's Anastigmat design where he replaced the front and back cemented groups with two-each air gap lenses. This was in the 1899 time frame when there were a limited number of glass types available to the lens designer. One of the problems with cemented elements is that if the index of refraction of both elements is the same, them the cemented boundary has no optical effect and the group becomes one lens. By splitting the elements with an air gap, Rudolph would have been able to use similar glass type for both lenses of a group without the above problem.

Kingslake claimed that the Unar was a good lens, but that Rudolph found that keeping the rear element as a cemented interface "had many virtues" and subsequently ended up replacing it in the rear group, thereby leading to his famous and highly successful Tessar design. Thus the Unar was a precursor to Rudolph's Tessar design, but there Kingslake's historical trail goes cold. Undoubtedly, the Unar design was not superior to the Tessar, or else the Unar would be a most common lens name. But it is possible that the performance of the two were on par and that the Tessar had other excellent properties (i.e. cost, ease of manufacture, etc.)

 

[Wade D]

If the price is right buy it and try it. With the bellows on the Graflex-D you should have no problem with infinity focus. Most of my old lenses are in US stops as well but once you get used to the conversion numbers it's not a big deal.

 

[Shangheye]

It's about $100....Does that constitute a reasonable price? It also seems to go to f128! It does look in excellent shape.

Thanks for the input guys...it always amazes me the knowledge on this site. Rgds, Kal

 

[Nicholas Lindan]

the Tessar had other excellent properties (i.e. cost, ease of manufacture, etc.)

The Tessar has 2 fewer glass-air surfaces, a really big plus in the days of no AR coatings. The main design push for the Dagor was to make a well corrected lens with only 4 glass-air surfaces.

I would think, other things being equal, a cemented pair will have a higher cost of manufacture than two separate lenses. But then the Unar may have required higher tolerances or more expensive glass.

 

[pgomena]

F/128 on the old US scale is F/64 on the modern scale. I have an old lens, too, and was amazed at first that it would stop down that far. Turns out that it's not so unusual when the scale is converted.

Peter Gomena

 

[outwest]

The US (Uniform System) scale doubles at each stop so they are marked 16, 32, 64, 128, 256. The US and f/ scales are equal at 16 so US 256 would be f/64.

 

[Ole]

US 128 is equivalent to f:45, not f:64.