TT&H added Iris.

[Eric Evans-4]

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Hello Group,

                 I just took down for cleaning, a brass lens, in pretty bad condition, that I have had for some years. On cleaning it up I discovered an inscription on the diaphragm ring:

 

                                  "IRIS ADDED BY T.T.& H. 10.1.98."

 

That must have been 1898, certainly wasn't 1998. I have never previously encountered anything like this, and am naturally curious to know a bit more.

    Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut and re-made into an iris diaphragm lens; was it an iris diaphragm lens that had a new iris added? What's the story, anybody? 

Eric.

[Marcel Safier]

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Eric

 

I have two examples of lenses that have had iris diaphragms added, one definitely was a waterhouse stop lens in its previous life. I cannot see any notations such as yours possesses though. Both are unbranded lenses. I have never seen a TTH waterhouse stop lens. Does anyone know if they made any? I suspect from the period they produced lenses, probably not.

 

Cheers!

Marcel
--
Marcel Safier (Photographic Historian)
PO Box 239
Holland Park 4121
Queensland Australia
http://members.ozemail.com.au/~msafier/index.html

 

-----Original Message-----
From: woodandbrass-bounces@... [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
Sent: 10 December 2007 06:59
To: woodandbrass@...
Subject: [W&B] TT&H added Iris.

 

Hello Group,

                 I just took down for cleaning, a brass lens, in pretty bad condition, that I have had for some years. On cleaning it up I discovered an inscription on the diaphragm ring:

 

                                  "IRIS ADDED BY T.T.& H. 10.1.98."

 

That must have been 1898, certainly wasn't 1998. I have never previously encountered anything like this, and am naturally curious to know a bit more.

    Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut and re-made into an iris diaphragm lens; was it an iris diaphragm lens that had a new iris added? What's the story, anybody? 

Eric.

[John Rushton]

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Hi Marcel,

 

The Lens Vademecum confirms that TTH did make lenses with Waterhouse Stops.

 

Best Wishes,

John

 

From: woodandbrass-bounces@... [mailto:woodandbrass-bounces@...] On Behalf Of Marcel Safier
Sent: 09 December 2007 23:39
To: 'Collectors of 19th Century Cameras & Photographica'
Subject: RE: [W&B] TT&H added Iris.

 

Eric

 

I have two examples of lenses that have had iris diaphragms added, one definitely was a waterhouse stop lens in its previous life. I cannot see any notations such as yours possesses though. Both are unbranded lenses. I have never seen a TTH waterhouse stop lens. Does anyone know if they made any? I suspect from the period they produced lenses, probably not.

 

Cheers!

Marcel
--
Marcel Safier (Photographic Historian)
PO Box 239
Holland Park 4121
Queensland Australia
http://members.ozemail.com.au/~msafier/index.html

 

-----Original Message-----
From: woodandbrass-bounces@... [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
Sent: 10 December 2007 06:59
To: woodandbrass@...
Subject: [W&B] TT&H added Iris.

 

Hello Group,

                 I just took down for cleaning, a brass lens, in pretty bad condition, that I have had for some years. On cleaning it up I discovered an inscription on the diaphragm ring:

 

                                  "IRIS ADDED BY T.T.& H. 10.1.98."

 

That must have been 1898, certainly wasn't 1998. I have never previously encountered anything like this, and am naturally curious to know a bit more.

    Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut and re-made into an iris diaphragm lens; was it an iris diaphragm lens that had a new iris added? What's the story, anybody? 

Eric.

 

 

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Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date: 09/12/2007 11:06

[Ole Tjugen-2]

I believe J. Lancaster held the British patent for iris apertures for  
quite a while in the late 19th century, so most other British lenses of  
that time were fitted with waterhouse stops. It seems to fit in with the  
lenses I have of that period - the Lancasters all have iris, others have  
Waterhouse- or wheel stops. And all Lancasters are marked with "Patent" -  
that patent I believe was for the iris, not the lens itself. :)

Ole Tjugen

På Sun, 09 Dec 2007 21:59:20 +0100, skrev Eric Evans  
<ericevans2@...>:

> Hello Group,
>                  I just took down for cleaning, a brass lens, in pretty  
> bad condition, that I have had for some years. On cleaning it up I  
> discovered an inscription on the diaphragm ring:
>
>                                   "IRIS ADDED BY T.T.& H. 10.1.98."
>
> That must have been 1898, certainly wasn't 1998. I have never previously  
> encountered anything like this, and am naturally curious to know a bit  
> more.
>     Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut and  
> re-made into an iris diaphragm lens; was it an iris diaphragm lens that  
> had a new iris added? What's the story, anybody?
> Eric.

[Eric Evans-4]

Some parts of this message have been removed. Learn more about Nabble's security policy.

Marcel and John and Ole,

                            Mine is an unbranded lens, apart from the "Added" inscription. Some questions, not necessarily only for the three of you, but for anyone else who wants to wade in:

 

    Did they refurbish only their own lenses? Or did they offer a "Re-diaphragm" service? If so, wouldn't it have been a toss-up as to whether the update was more expensive than the lens was worth? And surely it would have been an extreme precision job to get the separation between the front and rear elements exact, and also to get the aperture in exactly the right place? I think a person would have to be extremely attached to a lens to embark on such an alteration; TTH never came cheap.

    Maybe it was a prestige thing in the light of what Ole says; I guess there'd be some snob value in having a TTH converted lens, instead of buying a Lancaster in the first place?

Regards,

Eric.

----- Original Message -----

From: john_rushton@...

To: woodandbrass@...

Sent: Sunday, December 09, 2007 11:48 PM

Subject: RE: [W&B] TT&H added Iris.

Hi Marcel,

 

The Lens Vademecum confirms that TTH did make lenses with Waterhouse Stops.

 

Best Wishes,

John

 

From: woodandbrass-bounces@... [mailto:woodandbrass-bounces@...] On Behalf Of Marcel Safier
Sent: 09 December 2007 23:39
To: 'Collectors of 19th Century Cameras &amp; Photographica'
Subject: RE: [W&B] TT&H added Iris.

 

Eric

 

I have two examples of lenses that have had iris diaphragms added, one definitely was a waterhouse stop lens in its previous life. I cannot see any notations such as yours possesses though. Both are unbranded lenses. I have never seen a TTH waterhouse stop lens. Does anyone know if they made any? I suspect from the period they produced lenses, probably not.

 

Cheers!

Marcel
--
Marcel Safier (Photographic Historian)
PO Box 239
Holland Park 4121
Queensland Australia
http://members.ozemail.com.au/~msafier/index.html

 

-----Original Message-----
From: woodandbrass-bounces@... [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
Sent: 10 December 2007 06:59
To: woodandbrass@...
Subject: [W&B] TT&H added Iris.

 

Hello Group,

                 I just took down for cleaning, a brass lens, in pretty bad condition, that I have had for some years. On cleaning it up I discovered an inscription on the diaphragm ring:

 

                                  "IRIS ADDED BY T.T.& H. 10.1.98."

 

That must have been 1898, certainly wasn't 1998. I have never previously encountered anything like this, and am naturally curious to know a bit more.

    Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut and re-made into an iris diaphragm lens; was it an iris diaphragm lens that had a new iris added? What's the story, anybody? 

Eric.

 

 

No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date: 09/12/2007 11:06

---

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Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date: 09/12/2007 11:06

[Ole Tjugen-2]

The Vade Mecum says (about Lancaster): "They seem to have introduced the  
iris to the general market as a result of a Patent of 19/03/1886 although  
the general idea was not new- and was soon adopted by others, notably Wray  
and Beck."

The conversion is actually relatively simple, in that the slot for the  
Waterhouse stop is in the correct location for the iris mechanism. So the  
iris was merely inserted in the existing barrel, aperture markings added,  
and the slider went through the slot. It is not unusual to come across  
lenses where a damaged iris has been removed, and the slot adopted (not  
"adapted") for waterhouse stops.

I can well understand that having lenses converted to iris apertures would  
be attractive, after having tried to find the correct set of Waterhouse  
stops for a lens when I was going to use it!

Ole

På Mon, 10 Dec 2007 09:17:04 +0100, skrev Eric Evans  
<ericevans2@...>:

> Marcel and John and Ole,
>                             Mine is an unbranded lens, apart from the  
> "Added" inscription. Some questions, not necessarily only for the three  
> of you, but for anyone else who wants to wade in:
>
>     Did they refurbish only their own lenses? Or did they offer a  
> "Re-diaphragm" service? If so, wouldn't it have been a toss-up as to  
> whether the update was more expensive than the lens was worth? And  
> surely it would have been an extreme precision job to get the separation  
> between the front and rear elements exact, and also to get the aperture  
> in exactly the right place? I think a person would have to be extremely  
> attached to a lens to embark on such an alteration; TTH never came cheap.
>     Maybe it was a prestige thing in the light of what Ole says; I guess  
> there'd be some snob value in having a TTH converted lens, instead of  
> buying a Lancaster in the first place?
> Regards,
> Eric.
>   ----- Original Message -----
>   From: John Rushton
>   To: 'Collectors of 19th Century Cameras &Photographica'
>   Sent: Sunday, December 09, 2007 11:48 PM
>   Subject: RE: [W&B] TT&H added Iris.
>
>
>   Hi Marcel,
>
>
>   The Lens Vademecum confirms that TTH did make lenses with Waterhouse  
> Stops.
>
>
>   Best Wishes,
>
>   John
>
>
>   From: woodandbrass-bounces@...  
> [mailto:woodandbrass-bounces@...] On Behalf Of Marcel Safier
>   Sent: 09 December 2007 23:39
>   To: 'Collectors of 19th Century Cameras & Photographica'
>   Subject: RE: [W&B] TT&H added Iris.
>
>
>   Eric
>
>
>   I have two examples of lenses that have had iris diaphragms added, one  
> definitely was a waterhouse stop lens in its previous life. I cannot see  
> any notations such as yours possesses though. Both are unbranded lenses.  
> I have never seen a TTH waterhouse stop lens. Does anyone know if they  
> made any? I suspect from the period they produced lenses, probably not.
>
>
>   Cheers!
>
>   Marcel
>   --
>   Marcel Safier (Photographic Historian)
>   PO Box 239
>   Holland Park 4121
>   Queensland Australia
>   http://members.ozemail.com.au/~msafier/index.html
>
>
>   -----Original Message-----
>   From: woodandbrass-bounces@...  
> [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
>   Sent: 10 December 2007 06:59
>   To: woodandbrass@...
>   Subject: [W&B] TT&H added Iris.
>
>
>   Hello Group,
>
>                    I just took down for cleaning, a brass lens, in  
> pretty bad condition, that I have had for some years. On cleaning it up  
> I discovered an inscription on the diaphragm ring:
>
>
>                                     "IRIS ADDED BY T.T.& H. 10.1.98."
>
>
>   That must have been 1898, certainly wasn't 1998. I have never  
> previously encountered anything like this, and am naturally curious to  
> know a bit more.
>
>       Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut  
> and re-made into an iris diaphragm lens; was it an iris diaphragm lens  
> that had a new iris added? What's the story, anybody?
>
>   Eric.
>
>
>
>
>
>   No virus found in this outgoing message.
>   Checked by AVG Free Edition.
>   Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date:  
> 09/12/2007 11:06
>
>
>
>
> ------------------------------------------------------------------------------
>
>
>   No virus found in this incoming message.
>   Checked by AVG Free Edition.
>   Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date:  
> 09/12/2007 11:06

--

Ole Tjugen

[Eric Evans-4]

Hi Ole,
           I have seen the type of conversion you refer to, but the
alteration to "my" lens is much more complicated than the simple insertion
of an iris into the Waterhouse slot.
    The entire lens has been cut into two halves and the familiar TTH "broad
black banded" unit mechanism fitted, the whole screwed back together with
the iris in the middle.
    It must have involved re-threading the two halves of the brass tube, to
screw back together into either side of the iris; that process would have
meant that the thickness of the inserted band would have had to be allowed
for in the separation of the elements.
    If they were doing this to a variety of different sized lenses, the
individual cutting, turning and screw cutting must have been prohibitively
labour intensive, and, I imagine, prohibitively expensive as a consequence,
unless they had some sort of "mass production" set-up whereby a number of
pre-manufactured units were available in various sizes?
    Or maybe the "added" inscription merely means that they took out an
existing iris and replaced it with a standard item?
    This is for discussion, I don't expect any answers..........unless
somebody can come up with some contemporaneous references?
Regards,
Eric.
----- Original Message -----
From: "Ole Tjugen" <ole@...>
To: "Collectors of 19th Century Cameras &Photographica"
<woodandbrass@...>
Sent: Monday, December 10, 2007 8:47 AM
Subject: Re: [W&B] TT&H added Iris.


The Vade Mecum says (about Lancaster): "They seem to have introduced the
iris to the general market as a result of a Patent of 19/03/1886 although
the general idea was not new- and was soon adopted by others, notably Wray
and Beck."

The conversion is actually relatively simple, in that the slot for the
Waterhouse stop is in the correct location for the iris mechanism. So the
iris was merely inserted in the existing barrel, aperture markings added,
and the slider went through the slot. It is not unusual to come across
lenses where a damaged iris has been removed, and the slot adopted (not
"adapted") for waterhouse stops.

I can well understand that having lenses converted to iris apertures would
be attractive, after having tried to find the correct set of Waterhouse
stops for a lens when I was going to use it!

Ole

På Mon, 10 Dec 2007 09:17:04 +0100, skrev Eric Evans
<ericevans2@...>:

> Marcel and John and Ole,
>                             Mine is an unbranded lens, apart from the
> "Added" inscription. Some questions, not necessarily only for the three
> of you, but for anyone else who wants to wade in:
>
>     Did they refurbish only their own lenses? Or did they offer a
> "Re-diaphragm" service? If so, wouldn't it have been a toss-up as to
> whether the update was more expensive than the lens was worth? And
> surely it would have been an extreme precision job to get the separation
> between the front and rear elements exact, and also to get the aperture
> in exactly the right place? I think a person would have to be extremely
> attached to a lens to embark on such an alteration; TTH never came cheap.
>     Maybe it was a prestige thing in the light of what Ole says; I guess
> there'd be some snob value in having a TTH converted lens, instead of
> buying a Lancaster in the first place?
> Regards,
> Eric.
>   ----- Original Message -----
>   From: John Rushton
>   To: 'Collectors of 19th Century Cameras &Photographica'
>   Sent: Sunday, December 09, 2007 11:48 PM
>   Subject: RE: [W&B] TT&H added Iris.
>
>
>   Hi Marcel,
>
>
>   The Lens Vademecum confirms that TTH did make lenses with Waterhouse
> Stops.
>
>
>   Best Wishes,
>
>   John
>
>
>   From: woodandbrass-bounces@...
> [mailto:woodandbrass-bounces@...] On Behalf Of Marcel Safier
>   Sent: 09 December 2007 23:39
>   To: 'Collectors of 19th Century Cameras & Photographica'
>   Subject: RE: [W&B] TT&H added Iris.
>
>
>   Eric
>
>
>   I have two examples of lenses that have had iris diaphragms added, one
> definitely was a waterhouse stop lens in its previous life. I cannot see
> any notations such as yours possesses though. Both are unbranded lenses.
> I have never seen a TTH waterhouse stop lens. Does anyone know if they
> made any? I suspect from the period they produced lenses, probably not.
>
>
>   Cheers!
>
>   Marcel
>   --
>   Marcel Safier (Photographic Historian)
>   PO Box 239
>   Holland Park 4121
>   Queensland Australia
>   http://members.ozemail.com.au/~msafier/index.html
>
>
>   -----Original Message-----
>   From: woodandbrass-bounces@...
> [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
>   Sent: 10 December 2007 06:59
>   To: woodandbrass@...
>   Subject: [W&B] TT&H added Iris.
>
>
>   Hello Group,
>
>                    I just took down for cleaning, a brass lens, in
> pretty bad condition, that I have had for some years. On cleaning it up
> I discovered an inscription on the diaphragm ring:
>
>
>                                     "IRIS ADDED BY T.T.& H. 10.1.98."
>
>
>   That must have been 1898, certainly wasn't 1998. I have never
> previously encountered anything like this, and am naturally curious to
> know a bit more.
>
>       Was it a Waterhouse stop lens that Taylor, Taylor and Hobson cut
> and re-made into an iris diaphragm lens; was it an iris diaphragm lens
> that had a new iris added? What's the story, anybody?
>
>   Eric.
>
>
>
>
>
>   No virus found in this outgoing message.
>   Checked by AVG Free Edition.
>   Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date:
> 09/12/2007 11:06
>
>
>
>
> --------------------------------------------------------------------------

----
>
>
>   No virus found in this incoming message.
>   Checked by AVG Free Edition.
>   Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date:
> 09/12/2007 11:06



--

Ole Tjugen




--
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.16.17/1179 - Release Date: 09/12/2007
11:06

[Milan Zahorcak*]

Eric,

A couple of companies offered "after market" iris diaphragms, but you rarely
see any of the conversions.

Around the time that lenses with installed iris diaphragms were coming on
the market (late 1880s, early 1890s), most lenses already had stops of some
sort - typically a stop-wheel.  I would guess that few favored lenses
justified the risk or expense of converting to an iris.

Ole noted that Lancaster offered the first iris-equipped lenses; I think the
first was their Rectigraph lens in 1886 - a landscape lens found on many
Lancaster cameras.

Interestingly, also in 1886, another company took that one-step further.
Back when I was collecting early "add-on" shutters, one of my favorite
retrofits was not just an iris diaphragm, but an iris diaphragm shutter
(!!!) - three years before B&L introduced their soon-to-be Iris Diaphragm
Shutter.

This is a Benster Patent Diaphragm, c1887-88.

http://www.pacificrimcamera.com/milanpub/Misc-pics/Benster.jpg

It carries US patent 339,731 dated April 13, 1886 (!!!).  The ad shown is
from 1888.  There is also a nice cut-away illustration in the ad in the 1888
Gatchel reprint, page 75.

http://www.google.com/patents?id=dgVJAAAAEBAJ&pg=PP1&dq=339731#PPP1,M1

As you note, the installation required that the lens be cut apart and
reassembled around the shutter.  But it really isn't as easy as it sounds
(ha!) as they would have to maintain the cell spacing, etc.  Technically,
they would have to remove a thin ring of metal, not just cut the lens apart
- although I wonder if they actually did that.  Still, it is amazing what
they thought of as routine work in those days.

I've only seen three of these installed.  Mine came out of a wrecked
Dallmeyer 3-B, roughly 4" in diameter and had been silver-soldered in place.
Quite remarkable and much more massive than it looks in my crappy pic.

Regards,

mz  

> -----Original Message-----
> From: woodandbrass-bounces@...
> [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
> Sent: Monday, December 10, 2007 2:06 AM
> To: woodandbrass@...
> Subject: Re: [W&B] TT&H added Iris.
>
>
> Hi Ole,
>            I have seen the type of conversion you refer to,
> but the alteration to "my" lens is much more complicated than
> the simple insertion of an iris into the Waterhouse slot.
>     The entire lens has been cut into two halves and the
> familiar TTH "broad black banded" unit mechanism fitted, the
> whole screwed back together with the iris in the middle.
>     It must have involved re-threading the two halves of the
> brass tube, to screw back together into either side of the
> iris; that process would have meant that the thickness of the
> inserted band would have had to be allowed for in the
> separation of the elements.
>     If they were doing this to a variety of different sized
> lenses, the individual cutting, turning and screw cutting
> must have been prohibitively labour intensive, and, I
> imagine, prohibitively expensive as a consequence, unless
> they had some sort of "mass production" set-up whereby a
> number of pre-manufactured units were available in various sizes?
>     Or maybe the "added" inscription merely means that they
> took out an existing iris and replaced it with a standard item?
>     This is for discussion, I don't expect any
> answers..........unless somebody can come up with some
> contemporaneous references? Regards, Eric.

[Eric Evans-4]

Hi Milan, et al.
           "What shall we do today, daddy?"
"Well, today son, we'll take this valuable lens that some sucker has sent
us, tear it in two halves and put an iris/shutter in. We haven't got an
iris/shutter yet? So, we'll invent one and build it, exactly to
size..........pass me that sheet of brass, son........then, after breakfast,
we'll have a go at building a locomotive engine............."
    Those were the days. And apart from my obvious facetiousness, it seems
that there was probably far less in the way of "Cottage industry" than we
are apt to believe; these guys must have been well organised on an
industrial basis, and using a mail order system that worked.
    Thanks for your valuable insights, as ever, Milan, and another question
springs to mind: was the spacing between the two cells of a rapid
rectilinear all that precise, or was it expandable and contractable, within
certain tolerances? Maybe I have just discovered the zoom lens.........?
Thanks and regards,
Eric.

----- Original Message -----
From: "Milan Zahorcak" <milan.zahorcak@...>
To: "'Collectors of 19th Century Cameras &Photographica'"
<woodandbrass@...>
Sent: Tuesday, December 11, 2007 6:54 AM
Subject: RE: [W&B] Other added Iris.



Eric,

A couple of companies offered "after market" iris diaphragms, but you rarely
see any of the conversions.

Around the time that lenses with installed iris diaphragms were coming on
the market (late 1880s, early 1890s), most lenses already had stops of some
sort - typically a stop-wheel.  I would guess that few favored lenses
justified the risk or expense of converting to an iris.

Ole noted that Lancaster offered the first iris-equipped lenses; I think the
first was their Rectigraph lens in 1886 - a landscape lens found on many
Lancaster cameras.

Interestingly, also in 1886, another company took that one-step further.
Back when I was collecting early "add-on" shutters, one of my favorite
retrofits was not just an iris diaphragm, but an iris diaphragm shutter
(!!!) - three years before B&L introduced their soon-to-be Iris Diaphragm
Shutter.

This is a Benster Patent Diaphragm, c1887-88.

http://www.pacificrimcamera.com/milanpub/Misc-pics/Benster.jpg

It carries US patent 339,731 dated April 13, 1886 (!!!).  The ad shown is
from 1888.  There is also a nice cut-away illustration in the ad in the 1888
Gatchel reprint, page 75.

http://www.google.com/patents?id=dgVJAAAAEBAJ&pg=PP1&dq=339731#PPP1,M1

As you note, the installation required that the lens be cut apart and
reassembled around the shutter.  But it really isn't as easy as it sounds
(ha!) as they would have to maintain the cell spacing, etc.  Technically,
they would have to remove a thin ring of metal, not just cut the lens apart
- although I wonder if they actually did that.  Still, it is amazing what
they thought of as routine work in those days.

I've only seen three of these installed.  Mine came out of a wrecked
Dallmeyer 3-B, roughly 4" in diameter and had been silver-soldered in place.
Quite remarkable and much more massive than it looks in my crappy pic.

Regards,

mz

> -----Original Message-----
> From: woodandbrass-bounces@...
> [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
> Sent: Monday, December 10, 2007 2:06 AM
> To: woodandbrass@...
> Subject: Re: [W&B] TT&H added Iris.
>
>
> Hi Ole,
>            I have seen the type of conversion you refer to,
> but the alteration to "my" lens is much more complicated than
> the simple insertion of an iris into the Waterhouse slot.
>     The entire lens has been cut into two halves and the
> familiar TTH "broad black banded" unit mechanism fitted, the
> whole screwed back together with the iris in the middle.
>     It must have involved re-threading the two halves of the
> brass tube, to screw back together into either side of the
> iris; that process would have meant that the thickness of the
> inserted band would have had to be allowed for in the
> separation of the elements.
>     If they were doing this to a variety of different sized
> lenses, the individual cutting, turning and screw cutting
> must have been prohibitively labour intensive, and, I
> imagine, prohibitively expensive as a consequence, unless
> they had some sort of "mass production" set-up whereby a
> number of pre-manufactured units were available in various sizes?
>     Or maybe the "added" inscription merely means that they
> took out an existing iris and replaced it with a standard item?
>     This is for discussion, I don't expect any
> answers..........unless somebody can come up with some
> contemporaneous references? Regards, Eric.

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11:06

[Milan Zahorcak*]

Eric,

Cell spacing is one of a group of simultaneous applied variables in a lens
design.  The math becomes pretty intimidating quickly, but because it works
as part of a interconnected set, cell spacing becomes more or less critical
depending on how it affects the other variables, and how they affect it.

If we give the lens designer credit for doing the best possible job, for
"optimizing" the final design to make best use of those variables, then the
lens as built should be better than any further tweaking can make it.
Changing anything has to degrade the performance in some way.

However, how much the performance suffers depends on how large a role cell
spacing played, and some designs are affected much more by these changes
than others.

Kingslake wrote that Dagor type lenses suffered greatly from even small
deviations in spacing while RR lenses could tolerate up to a 1% variation
(which I suppose he considered a large variation) with little consequence.
He finished that section with the statement "In general, it is usually found
that the better the lens, the greater is the effect of an error in the
central airspace."

A few observations:

1.  a 1% error in a RR lens that is say 4" long (about 101.6 mm) is only
about 1 mm, or about 0.01" - and Kingslake considers that a lot - maybe a
1/2-turn of one of the cells?  Obviously, the smaller the lens, the more
critical that 1% becomes.

2.  I suppose you can test how good your lens is by unscrewing the cells a
turn or two - if the image doesn't change much, the lens was crappy to start
with?

3.  And if you recall this is how Dallmeyer introduced soft focus into their
Patent Portrait lenses.  You changed the spacing of the air-spaced pair at
the rear.  You unscrewed the rear cell by 1/4-turn increments.  One
full-turn was pretty soft.

Still, it is astounding craftsmanship from guys wearing ties and being paid
pennies an hour.  I love this image, the Dallmeyer finishing room in the
early 1900s.  Highly skilled labor - no doubt making small corrections . . .

http://www.pacificrimcamera.com/milanpub/Misc-pics/dallmeyer.jpg

mz


   

> -----Original Message-----
> From: woodandbrass-bounces@...
> [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
> Sent: Tuesday, December 11, 2007 2:15 AM
> To: woodandbrass@...
> Subject: Re: [W&B] Other added Iris.
>
>
> Hi Milan, et al.
>            "What shall we do today, daddy?"
> "Well, today son, we'll take this valuable lens that some
> sucker has sent us, tear it in two halves and put an
> iris/shutter in. We haven't got an iris/shutter yet? So,
> we'll invent one and build it, exactly to size..........pass
> me that sheet of brass, son........then, after breakfast,
> we'll have a go at building a locomotive engine............."
>     Those were the days. And apart from my obvious
> facetiousness, it seems that there was probably far less in
> the way of "Cottage industry" than we are apt to believe;
> these guys must have been well organized on an industrial
> basis, and using a mail order system that worked.
>     Thanks for your valuable insights, as ever, Milan, and
> another question springs to mind: was the spacing between the
> two cells of a rapid rectilinear all that precise, or was it
> expandable and contractable, within certain tolerances? Maybe
> I have just discovered the zoom lens.........? Thanks and
> regards, Eric.
>
> ----- Original Message -----
> From: "Milan Zahorcak" <milan.zahorcak@...>
> To: "'Collectors of 19th Century Cameras &Photographica'"
> <woodandbrass@...>
> Sent: Tuesday, December 11, 2007 6:54 AM
> Subject: RE: [W&B] Other added Iris.
>
>
>
> Eric,
>
> A couple of companies offered "after market" iris diaphragms,
> but you rarely see any of the conversions.
>
> Around the time that lenses with installed iris diaphragms
> were coming on the market (late 1880s, early 1890s), most
> lenses already had stops of some sort - typically a
> stop-wheel.  I would guess that few favored lenses justified
> the risk or expense of converting to an iris.
>
> Ole noted that Lancaster offered the first iris-equipped
> lenses; I think the first was their Rectigraph lens in 1886 -
> a landscape lens found on many Lancaster cameras.
>
> Interestingly, also in 1886, another company took that
> one-step further. Back when I was collecting early "add-on"
> shutters, one of my favorite retrofits was not just an iris
> diaphragm, but an iris diaphragm shutter
> (!!!) - three years before B&L introduced their soon-to-be
> Iris Diaphragm Shutter.
>
> This is a Benster Patent Diaphragm, c1887-88.
>
> http://www.pacificrimcamera.com/milanpub/Misc-pics/Benster.jpg
>
> It carries US patent 339,731 dated April 13, 1886 (!!!).  The
> ad shown is from 1888.  There is also a nice cut-away
> illustration in the ad in the 1888 Gatchel reprint, page 75.
>
> http://www.google.com/patents?id=dgVJAAAAEBAJ&pg=PP1&dq=339731#PPP1,M1
>
> As you note, the installation required that the lens be cut
> apart and reassembled around the shutter.  But it really
> isn't as easy as it sounds
> (ha!) as they would have to maintain the cell spacing, etc.  
> Technically, they would have to remove a thin ring of metal,
> not just cut the lens apart
> - although I wonder if they actually did that.  Still, it is
> amazing what they thought of as routine work in those days.
>
> I've only seen three of these installed.  Mine came out of a
> wrecked Dallmeyer 3-B, roughly 4" in diameter and had been
> silver-soldered in place. Quite remarkable and much more
> massive than it looks in my crappy pic.
>
> Regards,
>
> mz
>
>
>
>
>
> > -----Original Message-----
> > From: woodandbrass-bounces@...
> > [mailto:woodandbrass-bounces@...] On Behalf Of Eric Evans
> > Sent: Monday, December 10, 2007 2:06 AM
> > To: woodandbrass@...
> > Subject: Re: [W&B] TT&H added Iris.
> >
> >
> > Hi Ole,
> >            I have seen the type of conversion you refer to, but the
> > alteration to "my" lens is much more complicated than the simple
> > insertion of an iris into the Waterhouse slot.
> >     The entire lens has been cut into two halves and the
> familiar TTH
> > "broad black banded" unit mechanism fitted, the whole screwed back
> > together with the iris in the middle.
> >     It must have involved re-threading the two halves of the brass
> > tube, to screw back together into either side of the iris; that
> > process would have meant that the thickness of the inserted
> band would
> > have had to be allowed for in the separation of the elements.
> >     If they were doing this to a variety of different sized
> > lenses, the individual cutting, turning and screw cutting
> > must have been prohibitively labour intensive, and, I
> > imagine, prohibitively expensive as a consequence, unless
> > they had some sort of "mass production" set-up whereby a
> > number of pre-manufactured units were available in various sizes?
> >     Or maybe the "added" inscription merely means that they
> > took out an existing iris and replaced it with a standard item?
> >     This is for discussion, I don't expect any
> > answers..........unless somebody can come up with some
> > contemporaneous references? Regards, Eric.
>
>
>
>
>
> --
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