Emil Busch Petzval generation transition history: sampling needed to testify & modify

I am going to receive a new flavor of Emil Busch petzvals from Finland soon.
As I don't have this brand, I started to study Emil Busch petzvals since yesterday.

Here is the old thread relevent to this topic.
https://www.largeformatphotography.i...zval-Lens-Info

In this thread, the scope of focus is limited only to Emil Busch petzvals.

I collected the relevent Emil Busch catalogs and calculated FL and F-numbers based on the front and rear lens element opening diameters.
WHS necking in the barrel is ignored as the convention and convenience purpose for identification of samples.

I assume all units of the older catalogs are in
Preussian 1 Zoll = 26.15mm
Preussian 1 Linien = 2.179mm

Attached is the tentative pdf I made which shall be updated with new findings as usual.

I have already searched engraving images of Emil Busch petzval samples, but no corresponding info about serial numbers.
I want you guys to post samples with the front and rear lens element opening diameters, the optical layout, the serial numbers and any engravings on the barrel.
I shall match the samples to the table and where it fits in the column and row to testify and modify the table accordingly,
speculating the serial number bands, periods and so on given the generation period row in the table.

I have put some engraving patterns on late models but no serial numbers for the future research.

Thanks in advance for your help.

April 9th, 2024
It turns out that Back Focus focal length descritions are updated before 1875 catalogs.
BF+1/3*BF=FL is applied to the calculations for FL before 1875 catalogs,
as this 1/3 factors are derived and consistent having both BF's and FL's described in the 1875 catalog.

After 1875, the focal length descriptions are in cm, but the numbers are in BF based on the context in accordance with the previous catalogs to match the FL, given the following catalogs.

1880 Handbuch_der_practischen_Photographie,
1884 1893 1899 Ausführliches_Handbuch_der_Photographie

After these catalogs, the focal lengths are described as FL, not BF, as in the following catalogs.
1904 1909 Emil Busch catalog (UK in inches)
1912 BUSCH PROJECTION AND, ENLARGING LENSES (UK in inches)

Attachment 250034

My sample has arrived.

I identified it as
System I FL 418mm f4
with Portrait und
Landschafts-Köpfe with WHS.

Or equivalently in the older period,
No.11 FL 418mm f4
with Portrait und
Landschafts-Köpfe with WHS.

meaning convertible.

The optical layout is the traditional petzval layout.
The front and rear element opening diameters are both 102mm.

The dating is still difficult as Busch engraved the specifications on the flange, including the serial number.

According to my research, I narrowed in that my new sample would be made in between 1866 and 1870.

Busch didn’t maintain the lens numbering consistency like Voigtlander, but
maintained the petzval lens element diameters hence barrel size throughout the productions from the beginning around 1850 to the end in about 1910.

VIII on the parts and barrel.

Count the unique front diameter in linien that indicates the front element diameter from the smallest number to 48”’ in the catalogs attached 1856 and 1859.

The count is 8, which matches to VIII on the barrel and parts. So VIII stands for the barrel size standard, much like Zeiss patent barrel standard.

Thanks to Karl French for his sample engraving pics.

Attachment 247827
Attachment 247828
Attachment 247829
Attachment 247830
Attachment 247831
Attachment 247832
Attachment 247833
Attachment 247834

What a super lens - and just the right size for 8x10 without being nervous about coverage!
It is obvious that Busch wanted to try just every feature novel feature that was being launched in Paris.
I am not convinced about the 8/VIII argument. Why on earth should the brass parts be labeled as to size - when the workshop staff have the items in front of them. Difference in size is immediately apparent. I have many component items with similar Roman numerals - especially French lenses of this period - which is obviously the source of Busch’s designs. Nine every case, it is a matching mark for female/male threads that fit well. This is still a period of hand, rather than machine cutting of threads, is normal.

Good evening from Tokyo, Steven.
Thanks for your comment.
What would be the Greek numerals on the barrel, waterhouse ring inside the barrel, lens case and so on in your opinion?
Until I started this study, I didn’t know Busch made probably the fastest petzvals for both short and long FL’s …..
I thought Dallmeyer 3C is the fastest, but not now….
But I have never seen the fastest Busch petzval pics online yet….

Well, perhaps not fitting matching, but perhaps ensuring identity BEFORE use of serial numbers.
In other words - this is the 8th lens made in a batch of 8 (or 10 or 12) made in the workshop of this particular size.
A number of Wien competitors to Voigtlander made super fast Petzvals to differentiate themselves from the Josef product.
I have Waibl which is well under F3.

Good evening, Steven.
I have just updated the pdf.
Oh wow, a nice Waibl! BTW, do you know anything about Wcaibl?
Yes, I understand minor brands were striving for the marketing differentiations against Major brands, Voigtlander and so on.

I shall examine other samples in the same period to see any rules about these Greek number engravings.

Another petzval has arrived home for sampling.

RATH.OPT.JND.ANST. vorm.EMIL BUSCH.
RATHENOW. Portrait Doppel-Objectiv No.5 III Foc.23cm
has been confirmed as below.

Front lens opening diameter 77.2mm
Rear lens opening diameter 77.2mm

Whole lens element diameter 80.7mm

The focal length is measured exactly 230mm.

No Greek numbers on any parts.

This lens is the No.5 of System III, non convertible petzval.
The dating is probably from 1878 to 1898 based on the engraving style.

Another sample inspection has been done.

Emil Busch A-G Rathenow
Portrat Doppel-Objectiv F:3 No.8 F=420mm.
The aperture scale min is f4 and it matches to the end of the wide open iris.
Rigid mount made of brass are painted black.
The front and rear lens cases are made of Aluminum and painted black.

The whole lens diameters are 108mm.
The opening lens diameters in the lens cases are 105mm.

This sample is one of the last generation that Busch made with the Jena glass,
as advertised in Busch London catalog, 1912 BUSCH PROJECTION AND, ENLARGING LENSES.

This sample was made after 1910’s. Busch ads searched online are listed even in 1920’s,
so the last generation must be made until 1920’s.

F3 advertisement even for longer FL is typical for most brands,
but the actual speed is less, similar to Dallmeyer A and B series, Hugo Meyer Atelier Schnellarbeiter, and Voigtlander Portrait-Objectiv I and so on.

The catalog states 17” f4 lens for this sample,
but 17” is a bit longer compared to 420mm.
It’s a typical rounding interpretation from German or metric system to English inch system.