CZJ Apo Germinar - what do these dials do?

[Steven Tribe]

I have had quite a few process lens through my hands (thanks to the sad closing of reproduction establishments) so I know about extra slots for filters etc. But this Apo Germinar 375mm F9 has me baffled. I have read Arne Croell's article and can see that this model was not continued by Docter Optics - perhaps for a very good reason! At the rear of the front element there is an engage/disengage button. This allows a ring to be turned which is goes from 1000% to 10%. Nearer the front is another ring that moves independently and has a double scale Rw and Rs which go from 24 and 25 resp. up to 100 and down to 2.3. At the end of these parallel scales there are Lin/cm and mm.

My guess is that is some kind of optimisation for "magnification" but can see no movement of the front lens cell. But there could be movement of the rear lens in the front cell of this dialyt?

Any ideas/knowledge would be gratefully received.

[Steven Tribe]

A photo always helps?

[Sevo]

Rw/Rs are Rasterweite respectively Rasterschritt. Similar tables are often attached to German process cameras, used to determine the appropriate f stop and defocus for rasterizing at a given pitch and magnification (usually only valid for one grid, film and process). It probably is a calculator scale only - I haven't ever encountered a process lens that controlled rasterization though moving elements, and if such a thing ever existed, it would hardly have been from the GDR.

[Steven Tribe]

Thanks Sevo - I had thought about rasters. And the ring with these markings is basically a loose ring that can be turned around - but does click into fixed positions opposite readings on the Rw/Ra scale . The % scale has a red dot position (at 200%) which clicks into a corresponding red dot at an aperture around F20.

[J. Patric Dahlen]

Rw/Rs are Rasterweite respectively Rasterschritt. Similar tables are often attached to German process cameras, used to determine the appropriate f stop and defocus for rasterizing at a given pitch and magnification (usually only valid for one grid, film and process).

Would this be for blurring an already rastered picture (from a book or newspaper, for example) to re-raster it? Geez, I wish I knew all the technical words in english. :rolleyes:

[Sevo]

Would this be for blurring an already rastered picture (from a book or newspaper, for example) to re-raster it?

It could be used for it, and probably still was, long after the early halftone rasterizing processes became obsolete. Originally it must have been a more central feature in rasterizing processes.

Raster sheets were already being replaced by drum scanners and lith sheet photoplotters when I learned printing around 1980. We still used a analogue raster process camera at art school, where a (already computer generated/photoplotted) raster sheet placed in contact with the film determined the shape, pattern, contrast and pitch of the halftone raster. I only have somewhat vague textbook knowledge about earlier raster processes, which employed physical sieve-like structures whose blurred projection was superimposed on the photograph to create a raster. In these processes, the shape and size of the aperture, defocus and grid offset were critical and used to control the properties of the raster - in West Germany they were obsolete in lithography by the sixties, but some relics survived in high end or large scale letterpress and rotogravure systems where a more tunable raster process was considered useful. In East Germany, they may have lingered on for much longer.

[Steven Tribe]

I'll try and take of the front element tomorrow to see if movement in the % scale actuals repositions the second lens in the front pair. Perhaps 1000% means 10/1, 100% means 1/1 and 10% means 1/10?

[Sevo]

Possible, but if so it would be slightly odd that there are no markings for the multiples of sqrt(2), the most common enlargement/reduction factors in the German print industry.

[J. Patric Dahlen]

Raster sheets were already being replaced by drum scanners and lith sheet photoplotters when I learned printing around 1980. We still used a analogue raster process camera at art school, where a (already computer generated/photoplotted) raster sheet placed in contact with the film determined the shape, pattern, contrast and pitch of the halftone raster.

Oh, some small printing shops still use the old analogue method with a process camera, raster sheets and "Copyproof" paper and film. I worked with that for a short while some twenty years ago, but don't remember much about the process. The camera we used was computer-controlled with autofocus. I don't remember if we had to calculate the blurring needed for raster originals, or if the computer could do that.

The contact raster sheet was a great invention. It has a continuos grayscale between the dots, so the more light going through it the more the dots on the lith paper/film would grow.