PDA

View Full Version : Is it common to see handwriting on lens element edges?



Tom Keenan
26-Dec-2009, 14:14
I admit that I have not disassembled many older brass lenses but recently I took an old petzval lens apart to clean. Both lens groups are "signed" on the unpolished edge of the glass. It is my understanding that many of these lenses were sold with no exterior markings so was it common to add an interior manufacturer "mark" or "signature" to these vintage lenses? Or is it more likely that an owner of the lens just wrote something there to keep the elements organized or something?
Thanks
Tom Keenan

Steven Tribe
26-Dec-2009, 14:23
This is a french speciality. Most Jamin Darlot - but yours is a Hermagis! Made by the finishing section by the maker in 18xx.

CCHarrison
26-Dec-2009, 14:51
It is not uncommon to see this....Darlot lenses seem to be most frequently mentioned as having markings... for some firms it may represent a "quality control" type of mark, while in other cases it could signal a repair, or even an inventory marking..

Dan

Steven Tribe
26-Dec-2009, 14:52
Your lens was probably not sold as a Hermagis. They were pretty good at engraving their objectives with very large letters! There are three possibilities:

- It is a clone, non-branded, version of one of their own 2 petzval portrait series lens.

- It is an order for a series of objectives, with some differences from their usual offerings, from a camera maker/retailer - most of these did put their own name on the lens, though.

- Hermagis just supplied the optics to another maker (perhaps, not even French) of objectives. There are a couple of names in French lenses who seen to have done nothing themselves but just bought-in the finished brassware and optics and were most interest in marketing.

The absence of exterior marks might indicate an earlier life as a projection lens. Photo?

Tom Keenan
26-Dec-2009, 15:24
I have always thought that the lens was a projection lens because it looks like it was removed from somewhere. It does have a slot on the opposite side for a stop.
Thanks
Tom Keenan

Steven Tribe
26-Dec-2009, 16:09
I would think this lens was sold as an Hermagis after all, as the outer casing with the tangential focussing drive was there - but has been lost. This casing, with flange thread, is where the distinctive Hermagis engraving would have been. Projection lenses don't have waterhouse stops unless made by a previous owner. The front doesn't look right for an early (portrait) photographic petzval - unless something is missing. The bigger it is - the more likely it is to be early.

Tom Keenan
26-Dec-2009, 17:34
Thanks for the info. I think the next step is to load up some film and see what the images look like. Does the "tangential drive" do anything except vary the distance of the entire unit from the film plane??
Thanks
Tom Keenan

Gordon Moat
26-Dec-2009, 22:44
Looks like the lens hood and the barrel would be missing, if this is a Petzval type design. The first image of the cemented elements would likely be the front group of a Petzval. If the rear group is two separate elements with a spacer between them, then even more likely. If you can get it mounted to a camera, then you could probably work without the radial drive. The important part is those lens elements.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

Steven Tribe
27-Dec-2009, 03:34
Tom - early cameras were pretty rudimentary as far as adjustment. Often basically interlocking boxes - or the adjustments on the base were loosening bolts and friction movement. So manufacturer's of lenses allowed for focussing through a turn screw which engaged in the toothed rail on the barrel to allow the barrel to move in and out of focus. The system became less important on cameras as they became more complex and better made. There were two types, the tangential (which is far commoner and the axis of the adjusting screw is at a tangent to the circumference of the barrel) and the radial ( uncommon - just a few makers- and where the turning axis points directly towards the centre of the barrel). Lenses in the 20th C used helicoil mounting threads to acheive the same movement.

Steven Tribe
27-Dec-2009, 04:56
You can see a few photos of a complete Hermagis at the following:

http://www.liveauctioneers.com/item/3633894

If you remove the "outsides" and the front, the remaining barrel will look like yours. The description for this completed auction is very faulty, though.

Tom Keenan
27-Dec-2009, 06:37
Yes, looks very much like the lens in that auction minus the front hood, mounting flange and exterior frame. My lens meaures right around 12 cm. so that sounds about right also. Funny that an old lens can be missing all of those parts and still (probably) make some nice images! Well, thanks for sharing your knowledge. It is very helpful to me (and hopefully others). I never quite understood the need for geared focus on these lenses but your explanation makes everything clear for me.
Thanks again,
Tom Keenan

Tom Keenan
27-Dec-2009, 07:16
Gordon:
Yes the other lens group is two elements and a metal spacer. I am searching for Kingslake's book right now to make sure I assemble the lens correctly and then I will post some images. By the way, I finished Dan Brown's novel "The Lost Symbol" just last night. For those of you that have read it, you will understand my need to dicipher every series of numbers or symbols I see. So I am including another image of the writing on the lens edge. Is it a simple lot number or does it mean something?
Thanks
Tom Keenan

Jon Wilson
27-Dec-2009, 08:39
Gordon:
Yes the other lens group is two elements and a metal spacer. I am searching for Kingslake's book right now to make sure I assemble the lens correctly and then I will post some images. By the way, I finished Dan Brown's novel "The Lost Symbol" just last night. For those of you that have read it, you will understand my need to dicipher every series of numbers or symbols I see. So I am including another image of the writing on the lens edge. Is it a simple lot number or does it mean something?
Thanks
Tom Keenan

Tom,

Don't tell anyone, but the answer is sealed in the Vatican Archives :eek:
This lens was used by the Knights Templar to assist in the revealing secret messages which are the foundation of their organization and their mission. I enjoy Dan Brown's works too! :D

OR......at the very least you have yourself a nice little petzval. Try to post some pics taken with it.

Jon

goamules
27-Dec-2009, 08:42
Tom, I have a Hermagis this size, and it's a great lens. Actually, several French makers marked their glass, and I knew you had a Hermagis Petzval as soon as I saw your first post. Mine actually has the name, and some numbers too. I always assumed my number xxxx 83 meant 1883, but I could be wrong. It's my favorite lens this size.

Assembly is easy, there are pictures online in places, or if you can see my avatar here:
http://www.flickr.com/groups/868027@N25/

Garrett

Steven Tribe
27-Dec-2009, 08:44
Could be:

-internal production reference number which could be same as the serial number (these are know to exist). Hermagis did not always have a serial number.

-focal length of this front achromat lens measured in mm.

The second group could mean anything. The quality control man or even which petzval lens it was for (F4 design ?).

Discussion on literature topics is, I believe, allowed on this site - but I don't think my opinion on Brown's confused and "borrowed" fiction would be allowed!!

goamules
27-Dec-2009, 08:53
The front doesn't look right for an early (portrait) photographic petzval - unless something is missing. The bigger it is - the more likely it is to be early.

Steven, where are you getting some of your information? Because people read these posts even years later, it's important to give factual information.

1. This lens was a portrait lens, because that's what petzvals were invented for - speed and sharpness to make sittings quicker. Just because it's missing the hood doesn't change what it is. Also, I've never seen a Hermagis magic lantern lens that was solid brass and with a focus. Tons of Darlots though.

2. Larger size has nothing to do with age of early optics. As a matter of fact, the opposite is sometimes true. The early daguerreotypists shot tiny 1/9 and 1/6 plates mostly. Even in the wet plate era, gem and small plates were the major, predominant size shot, and the lenses made. Very few could afford larger than halfplate lenses, and as the size goes up, fewer and fewer were made. Size has nothing to do with how early a lens is.

Garrett

Steven Tribe
27-Dec-2009, 10:55
Information about waterhouse stop came late in this thread. I confirmed it was a portrait lens immediately. I think that talking about projection lenses at the start was realistic. Not many portrait objectives have lost their casings and have become anonymous - apart from the marks on the side of the lens.

When I mentioned " early lenses", I meant, the earliest possible date for this Hermagis lens - which must be around 1865. By late, I mean the 90's with the introduction of mass private photography. The average size of studio photos is larger than the average size amateur photos. Certainly the privately taken photos of my own family from the late 90's are much smaller than the studio photos from the early 90's and 80's which are all are cabinet size or larger. I know there were lots of multi-lenses in use in studios - but this Hergamis is obviously not taken out of one of these.

It could be that the proportion of large/small lenses of the petzval portrait type didn't change from 1865 - 1895, but the chances are that more of the older smaller (cheaper) lenses would have been thrown away while the larger (more expensive) lenses would have survived even as just paperweights or doorstops.

Hergamis does seem only to have sold projection lenses after 1900 under their own name (VM) - but that doesn't mean they didn't supply components to others with their lens identification inside.

Gordon Moat
27-Dec-2009, 14:52
Gordon:
Yes the other lens group is two elements and a metal spacer. I am searching for Kingslake's book right now to make sure I assemble the lens correctly and then I will post some images. By the way, I finished Dan Brown's novel "The Lost Symbol" just last night. For those of you that have read it, you will understand my need to dicipher every series of numbers or symbols I see. So I am including another image of the writing on the lens edge. Is it a simple lot number or does it mean something?
Thanks
Tom Keenan

One of the best, if you have trouble finding Kingslake, is a French website with lots of lenses. There is a great drawing of a Petzval type lens on this page:

http://dioptrique.info/OBJECTIFS1/00003/00003.HTM

I would be more inclined to consider the first number a lot number, or perhaps the serial number, because these lenses were likely hand fitted, then assembled and tested. That might indicate that the second number would indicate four elements to assemble, or maybe something else about the construction. More interesting to me is that little arrow mark, which might help you out in reassembly.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

Tom Keenan
27-Dec-2009, 15:50
OK. Thanks for all the help. I cleaned and assembled the lens, took it in the back yard, focused on an object at infinity and measured the distance from the waterhouse slot to the ground glass. It measured 190mm. Then I measured the inside diameter of the front metal ring that holds the front element in place and it measures 58 mm. So 190/58 = f3.3 Is that right. Does all that look about right?
Tom Keenan

Steven Tribe
27-Dec-2009, 16:10
Yes it does. The 2 series Vademecum mention are F3.4 to F4.2 range (depending on focal length) and F2.7 - F4.2. The smallest size they mention is for 1/4 plate - efl =250mm. These 20th C offerings. For todays use of petzvals they will cover much more. Now the real work starts: making the stops and some kind of mounting system.

Tom Keenan
27-Dec-2009, 16:20
Should I make a stop? Maybe start with a nice 5x7 portrait...should I go down 1/2 stop? 1 stop? What do you think as a starting place? What about wide open?
Tom Keenan

Gordon Moat
27-Dec-2009, 16:45
I would just start with wide open, no Waterhouse stops, since this was the original idea of these portrait lenses. You might find you really like the results that way.

Ciao!

Gordon Moat Photography (http://www.gordonmoat.com)

Tom Keenan
22-Jan-2012, 12:41
Just think, if this was a digital forum and I waited 2 years between posts, all of my equipment would be obsolete.

The image on the left is shot wide open and the right image is with a primitive 1 stop cardboard stop just to get some idea about depth of field. Both shot on 4x5 Efke 100. Also my first experience with D-23 developer. Kind of a dreamy look. I think I will o one more series with a slightly smaller stop and then move on to a better subject. Any comments or suggestions ??
Tom Keenan

Steven Tribe
26-Jan-2012, 03:22
Well done Tom.
2 years is no time at all - in our world of aged objectives.
You will get more response if you post in a suitable thread in "image sharing".

AndyJ
27-Jan-2012, 03:17
Relevant blogpost (http://www.lensrentals.com/blog/2012/01/serial-numbers-circa-1870) over at Lensrentals. I'm becoming a bit of an optics geek, so seeing that, then this old thread, is interesting to me.

Anyway, nice shots, Tom. In the spirit of science and photography, I can only suggest to keep experimenting!

Tom Keenan
27-Jan-2012, 09:12
I will get this figured out. Here's one from last night. I used my morning K-Cup to trace a cardboard stop.
Tom Keenan