B&L Portrait Plastigmat 15 inch F:5.6, TLC and some history

January 27, 2018  •  Leave a Comment

B&L introduced the B&L Portrait Plastigmat series in 1921 as an entry in the soft focus pictorial lens segment.

Below is an add and a marketing blurb from the days found on the Soft Focus lens pages from Dan Colucci's website. (Link at the bottom of this blog)

The lens was introduced in 4 focal lengths, 9", 12", 15" and finally 18" for 8x10 studio camera work.  The shorter focal lengths were designed to mount on Graflex SLR cameras.

I collected four 15" EFL specimens of this lens over the last few years and recently a 12" EFL lens was added to my Portrait Plastigmat collection.

Four of the same focal length seems over the top from a collection or user perspective but they've come so far in three different flavors.

One 15" EFL (and also the 12" EFL) has a rear glass and a front glass.  The front glass doesn't seem to have any magnification but is there to increase or introduce more spherical aberrations.  The rear glass does most or all of the soft focus work through spherical aberration.

Then I have three 15" EFL Portrait Plastigmats with only rear glass.  There is no thread provision in the hood nor body to screw a front cell in, so the conclusion was, supported by other online commentaries, they were designed and built that way.  

Out of the 3, one comes with a wide barrel, two have a "skinny" barrel and these are the lenses I'll illustrate below.

The lens at left is complete, the lens at right is obviously not.

The hood screws into the iris cell and the iris cell screws into the barrel.  I confirmed the iris and barrel are transplantable to the lens on the right.  Serial numbers are left to right respectively 3196808 and 3197967.  One can also observe the lens flange thread to be at different location on the barrel.

Another view of the 3196808 with hood removed.

SImilar to my previous blog posts on fixing up the A. Ross #1520 landscape lens, I decided to run through my spare part boxes to find an iris I could use to restore functionality to the the lens with missing iris and hood.

Luck was once more at my side this time as I had another Rodenstock add-on iris for a TV-Heligon lens.  These came in a few different sizes and I found one that was suitable for conversion with a minimal amount of machining.  Took 15 minutes to mount on a lathe, machine the inside out for proper diameter and at the same time provide a stop.  Rodenstock iris provenance was removed at the same time.  M2 set screws with nylon tip to secure the iris with minimal impact to the original finish of the lens.  The f1.1 to f8 aperture scale on the iris is no match but since this is a relative indication, it does allow to calculate quickly what the real aperture is.

This particular iris covers 6 stops in half-stop clicks and wide open the aperture is the same as the original design, F:5.6 ... optical design is maintained as the iris is in about the same location, +/- 2mm.

Although the lens was designed for full plate coverage, the ground glass image at portrait distance on 8x10 format looks great with no noticeable vignetting.

Feed back and questions welcome !

Link below to Dan Colucci's excellent and very informational website for Soft Focus and vintage lens and camera information.  The link points to the article where the B&L Portrait Plastigmats are discussed.

Antique Cameras - Soft Focus Lenses Part 3

Cheers,

Rudi A.

 

 

 

 


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