Berthiot portable Aplanat Casket set?

[Steven Tribe]

I have searched the usual sources, but can find nothing about aplanat sets.
This has 4 separate lenses which can be screwed together when not in use and placed in a tight brass can. Focal lengths are 16, 25, 28 and 54 cm.
Lens is engraved size 3 bis and the fixed aperture (wheel stops) is only 1.5cm. Serial number (if this is meaningful!) is 33606.
My guess is that this is a portable aplanat (F around 16) with perhaps suggested use of single lenses as a landscape meniscus?
It came on an 18x24 French "Chambre Touriste" and certainly looks like the original fitment.
Both guesses and facts would be useful?

[CCHarrison]

Steven, perhaps this will help

http://books.google.com/books?id=ffMEAAAAYAAJ&pg=PA163&dq=Berthiot+Aplanat&hl=en&ei=r3DTTprLJcXe0QGOjJw_&sa=X&oi=book_result&ct=result&resnum=10&ved=0CFQQ6AEwCQ#v=onepage&q=Berthiot%20Aplanat&f=false


Dan

[alex from holland]

i always find that strange. with some links i am able to see and read the book and somtimes i am not able to read it. Has that something to do with any law ??

Sorry steven, for this question ...

I have looked it up in my berthiot cataloque, but your lens is much older
(my cataloque is dated about 1920)

[CCHarrison]

try google searching

Berthiot Objectiv-Satz

best
Dan

[Steven Tribe]

The 4 pages starting 151 look interesting! But Eder is difficult (and expensive) to get hold of!

[Steven Tribe]

Using your tips and my own Google variations, I have found plenty of references from books, photography journals etc. for Berthiot's Aplanat casket sets from around 1885 onwards.
Extracts from books used to be a page or so - now it is 2 or 3 lines, which gives absolutely no real information!

[Ole Tjugen]

I have searched the usual sources, but can find nothing about aplanat sets.
This has 4 separate lenses which can be screwed together when not in use and placed in a tight brass can. Focal lengths are 16, 25, 28 and 54 cm.
Lens is engraved size 3 bis and the fixed aperture (wheel stops) is only 1.5cm. Serial number (if this is meaningful!) is 33606.
My guess is that this is a portable aplanat (F around 16) with perhaps suggested use of single lenses as a landscape meniscus?
It came on an 18x24 French "Chambre Touriste" and certainly looks like the original fitment.
Both guesses and facts would be useful?

Well - let's think a bit:

16cm plus 25cm adds up to a combined focal length of about 97mm - which is VERY short for 18x24cm. And this doesn't look like it could be an ultra-wide-angle set.

The longest combination, 28 and 54cm, will give about 184mm - still far too short for the full 18x24cm.

The simple conclusion is that this set would be used with format reducing inserts, which was indeed very common at that time (my 24x30cm camera has inserts to reduce it to 18x24, 13x18, 10x15 and 9x12cm).

Full opening, 15mm at 97mm focal length is about f: 6.5 - quite plausible for an Aplanat. These sets have a tendency to have a max aperture suited (more or less) to the shortest combination, not the longest. Anyway with single cells it would take a very small aperture to reduce the aberrations to something a lens maker would find acceptable!

I don't have THIS set, but some of my Aplanat sets can be seen on http://www.casket-set.com :)

[Steven Tribe]

No sign that it has ever been used for smaller formats. No marks on the ground glass and only holder is for wet plate for 18x24 (front and back opening with tiny wooden slats and black canvas. The entry system for plates is double sided brass sliding strips which wouldn't have made later conversion to smaller formats easy. There is room enough for 3 further loose lenses in the cannister which could have been the higher focal lengths. I did the calculation of combined focal lengths too!
But it is marked as a no. 3 set which often means 18x24. I will try out the shorter types as landscape lenses and see how much they cover.

Later.
I have been naive enough to think that the numbers on the lenses represented the EFL!
This is not the case!
Focal lengths are approximate double in centimeters what is engraved on them.
What was Berthiot thinking or what clever idea in making conversion tables does this represent?

A possible solution is that the objective was fitted with a standard rear cell and the loose lenses were to be fitted on the front cell and the engraving on them gave the combined efl. This would also explain why the engraved number is followed by a C (ombination?) rather than CM?

[Ole Tjugen]

Have a look here: http://www.suaudeau.eu/memo/Fabre/fabre_objo/fabre-obj/139.html

That looks a lot like your set, doesn't it? And if so, it might be the lens diameters in mm that are marked on the cells. Don't ask me why...

[Steven Tribe]

Wonderful! 3 to 4 pages on it. Everything seems to match, including the extra thread for screwing the loose lenses together, the description of size no. 3 and the cannister storage.
Now I have to read it slowly with my French dictionary to the right of my mouse and try and understand the combination concept.

The text confirms my guess that the rear cell was fixed and unchanged - it is only the front cell which is changed. Very convenient for a field camera. There were originally 7 interchangable lenses. The sizes match mostly with the sizes shown for the size no. 3 in an illustration - with a little difference for some (mine is the no. 3 bis size).
The original fixed rear cell has been lost, but when I work out what the focal length that this must have been, I can perhaps use the nearest equivalent of the front lenses as a replacement. I am a bit surprised that this idea hasn't been reported outside of the French literature of the 80's/90's - but perhaps it wasn't so great optically?

Inspite of what the french text says, the marked numbers don't correspond to the actual lens diameter in mms.
The 54 does, that is, 54cm. But the smaller ones (like 25 and 29) are around 40mm. Perhaps the author had been enjoying the delights of Paris in the 1880's before returning to his office?

Merci, chère ami!

[Ole Tjugen]

I tried a search for Berthiot and casket set, then Objektiv-Satz, and Satzobjektiv, and then it dawned on me that this would be a "trousse".

Et voila!