History of Photography

Serial Numbers, Circa 1870

Published January 13, 2012

I had a fun surprise today. We were cleaning a couple of old Petzval lenses, getting them ready to show off at Imaging USA next week. One of our Darlot lens from circa 1870 or so gave us quite a surprise.


A pair of Darlot Petzval lenses, circa 1870

When we removed the elements to clean them, we found Darlot’s signature in pencil along the edges. That’s not unheard of, in the old days some Lensmakers were so proud of their lenses that they would sign the edge of the elements before inserting them.


Darlot's signature in pencil along the edge of the front element

The front element in this one also had a set of numbers along the edge that we didn’t understand until we took out the second element: it was also signed and had the same number. We assume this was Darlot’s version of a serial number (serial numbers etched into the brass came a bit later).


Identical numbers (group order transposed) on the other edge of the glass

At least that’s our best guess as to the explanation. But maybe someone out there has some more information. If you do, please leave a comment. Or better yet come visit our booth at imaging USA and you can take some pictures with it if you like (well, as long as you have a Canon mount camera) or just look at it if you don’t. And it works surprisingly well – the subject matter below leaves a lot to be desired, but I bet your current lens won’t work this well when it’s 140 years old.


Aaron at about 10 feet with small Petzval lens on 5D II


Joey at about 15 feet with the Darlot Petzval in this article


Author: Roger Cicala

I’m Roger and I am the founder of Lensrentals.com. Hailed as one of the optic nerds here, I enjoy shooting collimated light through 30X microscope objectives in my spare time. When I do take real pictures I like using something different: a Medium format, or Pentax K1, or a Sony RX1R.

Posted in History of Photography
  • Bruce

    Hi there,

    I have a similar Darlot Petzval lens. After I cleaned all the elements and put back one of the elements the wrong way, and result come out weird. A bit like yours, not only blurry but crazy swirly. Once I figured out and re-assembled it the image should be very sharp in the middle and creamy at the edges. I was using 6×6 and 4×5 film. I bet on your 35mm FF dSLR everything will be pretty sharp.


  • Joachim

    “Trial and error” was in the beginning of lens manufacturing the usual practice. Carl Zeiss and Ernst Abbé made a big change with some industrial impact by calculating microscopic lenses. That happened app. 1869. The calculation formulas were known before, a physicist named Fraunhofer designed a telescope 1819, 1840 did Petzval his work (and sold it to Voigtländer for a ridiculous amount of money, so that Voigtländer went away from Vienna/Austria to Braunschweig/Germany to avoid some legal problems with Petzval)

    The Carl Zeiss information is from Wikipedia ( http://de.wikipedia.org/wiki/Carl_Zeiss ), which is in German a much bigger article than in English – maybe Google can help to translate? And all that information I owe to Carl, whose wish of testing a Voigtländer 58mm gave the impulse to make a bit of research. Thanks, Carl!

  • Roger Cicala

    Thank you Joachim. That all makes perfect sense, and the dates would definitely be in the appropriate range if that’s the case. The trial and error fitting of components also makes sense, I do know the components were always tested together before assembly.

  • Joachim

    I forgot one other link that led me to the above:


  • Joachim

    Roger, do you already have a link to http://www.antiquecameras.net/1890lenscatalogue.html ?

    I’m not an expert in old cameras or lenses. So I’m only guessing:

    “8” is as well a symbol of “infinity”, if you turn it 90°
    In Europe we use metric system. 4592mm would be something like 180″, but 459.2 only 18,07″
    Which focus length is used for portraits with large size cameras?
    The numbers could be as well a date – in Europe is the format of a date, depending on a country, often D-M-Y – which could be 4th May 1892?
    But if two glasslenses have identical numbers, they are meant to fit together. At the time (at least, that’s what I recall from some researches in the net) there was no maths to calculate a lens with more glass-elements than two. So, they had to mock up the lens and try which worked best together.

  • Roger Cicala

    Not at all Zig, I enjoyed that very much. Gave me a smile.

    That makes some sense, but at the time Darlot was only making a few lenses, so it seems rather long for a part number. But perhaps batch numbers? The other similar lens didn’t have any numbers at all, but it seems to be a few years earlier, judging by the cruder stamping on the Brass.

  • Siegfried

    Dear Roger,
    this is me again. If I’m to be a tad more serious (which is of some difficulty for the nature of mine) then I’d guess that those numbers are not the serial numbers, but more part numbers + assembly instructions. I mean to say that they should be read as the following (e.g. for 8 4592 4683):
    – that’s part #4592
    – which must be installed after part #8
    – and followed by part #4683

    Please advise if there’re any 4592 4683 XXXX or XXXX 8 4592 ID’s on the other elements. Though due to the given age of those babies it may be not the easy (read: lucky) to find and read those identification signatures.

    Sorry for being a bad penny,

  • Roger Cicala

    Zig, that has got to be it. Now that I have Darlot’s phone number I’ll ring him up and see if he’ll do a guest blog.

  • Siegfried

    Dear Roger,
    obviously that’s an ancient phone number: 8 stands for long distance prefix (which is still in use in some countries), then there goes area code (4592 where 45 stands for Austria and 92 means Doebling) and finally it ends with local number (4683). Mister Petzval was known for his sense of humor and this perfectly explains why he put his phone number on the edge of the lens glass elements:
    – he was pretty much satisfied with the quality of the 1st element and put his phone number in a case the owner dismantled the lens for a service and would like to contact the manufacture (i.e. mr. Petzval) for instructions on how he should put those bits back together;
    – he wasn’t satisfied with what came out as the second element so he put he contact information in reverse. Formally he followed the rules saying that optical manufacturer must supply the product with his contact information since those ancient rules did not specify that those contacts must be clear and straight forward.


    This also explains why those two shots came out pretty blurry – I bet you used the second copy, not the 1st one.

    I didn’t put any smilies here. Should I? Please cut this post post script if my commend goes pretty clear w/o smilies (I believe you can edit approved post before posting them into your blog, can’t you?)

  • That is awesome!!

    Where did the lenses come from? Were they like hidden treasure you found somewhere in an old attic?

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