J.H. Dallmeyer 1888 Rectilinear Landscape No.2 - Disc apertures?

[dustspots]

I've just been rummaging through a box of lens parts I bought some time ago and discovered a J.H. Dallmeyer 1888 Rectilinear Landscape No.2 with perfect glass. It seems to easily cover 8x10 at around 10 inches. The lens obviously only has one cell and would have originally had an iris set in to the front - which is missing. I'd like to make some drop in disc apertures (or any other suggestion appreciated)... but need a little help on how to work out the hole sizes. I know how to work out sizes for a lens with two cells... but I'm stumped as to where to take the measurement from! Please help! Any other information about this lens or any of your experiences with it would be appreciated too! Thank you!

117655

[Steven Tribe]

The "usual" rectilinear no. 2 (patent) has, when complete, an equivalent focal length of 8.5" inches and covers 15x12". Dallmeyer did say in their catalogues that a single cell could be used.

I think yours is the more unusual "new in about 1888" Rectilinear Landscape lens (patent) where the no. 2 has a lens diameter of 1 3/4" and an equivalent focal length of 11.5". Coverage is just for full plate size. I imagine this model had the same system as the more ordinary (but very popular) landscape with screw-off (and thus lost!) wheel aperature/iris section.

If you have the serial number, I can do a search.

Working out the aperture sizes is very easy - but you will have to measure the existing diameter of the limiting "hole" at the front.

[dustspots]

Yes Steven, you are right about the size of the lens diameter... it is indeed 1 3/4", so it does seem to be 'the more unusual' no. 2 you describe! Perhaps that's why I haven't been able to find any information on it on the internet!

I'd very much appreciate any information you are able to glean from your J.H. Dallmeyer reference material... the serial number of the lens is 45008.

So glad to hear the process of working out aperture sizes will be easy! The limiting "hole" is 1 1/4" in diameter.

Thank you in advance!

[Steven Tribe]

I can't find the serial number! It should be easy - as one of the ledgers starts at 45,000. So the no. 2 rectilinear landscape should one of the first entries under that category! There are, indeed, many rectilinear landscapes after that serial number. Could you check the number again? I have found a few items which have been listed in the wrong lens type before - with a neat explanation made by Dallmeyer in 18xx!

Looking at the records, I can see that they didn't make very many of this lens type - after the initial burst of production in 1888 and 89.
And just a dozen or so the the bigger sizes (6 & 7).

Based on the focal length of 11.5" and the measured maximum aperture of 1.25" - the F is .... 7.36!
Which will produce a quite interesting non-perfect image.

Diameter of drop-in washers to produce F11 would be 11.5 / 11 = 1.045". For F16 11.5/16 = 0.72" etc.

It looks like there is room for a split ring to hold washers in position.

Interestingly, Dallmeyer called this a copying lens in their internal documents, so it must perform well when used at small apertures.

[Steven Tribe]

I have done a check of the numbers in the ledger book that starts at serial number 45,000 and it (45,008) isn't there - neither are the other numbers 45,000 - 45,010! It may be that these were "lost" in connection with some admin confusion in starting the new ledger. I am sure that if there was some doubt whether a serial number had been used, they would have given up a group of numbers to make sure they didn't send 2 identically engraved out of the plant.

[dustspots]

I just checked the serial number again and sadly it remains 45008 as previously stated, and therefore seems to be "lost" in mystery! I wonder why there weren't very many of this lens type made?

Thank you most kindly for working out the diameter of the drop-in washers for me... much appreciated! I'll make the appropriate washers over the next few days and give it a proper test run. I briefly tried it on my 8x10 as is, and you are quite right, it certainly does create an "interesting non-perfect image"! I'm looking forward to seeing what it will do at smaller apertures if it indeed is a true "copying" lens!

Yes, thankfully there is ample room for a split ring!

[Steven Tribe]

"interesting non-perfect images" are similar to the results of soft/pictorial lenses! Many owners of landscape meniscus lenses would be glad for the Dallmeyer design of being able to completely removing the front iris to get "expensive" pictorial possibilities! I'll post a few images of split retaining rings on other landscape lenses tomorrow.

Dallmeyer were very honest in their ledgers - I found an entry which said " and 3 others that were, unfortunately, not given serial numbers".

[Steven Tribe]

Here are 3 different versions of the retaining ring for front washer stops ( English, Irish and French!).

From the left,

1. Plain ring with an inwards lip. Grubb

2. Ring with 4 3/4's cuts - again with inwards lip. Darlot/Marion

3. Heavier duty ring with a single telescope section-like T cut. Ross. This has a fixed reduction washer at the base.


The inward lip is definitely a better idea than the Ross type.

A more sophisticated sytem would be a slightly undersized ring with a velvet seal.

[dustspots]

Thank you for posting images of the three different types of retaining rings for me. All are valid possibilities, but I think I might opt for the fourth option you mention, the undersized velvet sealed ring, mainly because it is less likely to wear the inner thread of the barrel mount, and also because the lip of the barrel has a very small inward indent which might impede an absolute light tight seal.

Before I go off and start this little project... I was just wondering if there is an optimum thickness required for the washer discs... would 1mm be too thick, and should I chamfer the edges at all?

Thanks again Steven... you've have been a great help!

[Steven Tribe]

I have always used brass - but there is no reason not to use good quality cardboard or aluminium.
Thickness of the "genuine" disc/washer stops I have is about 0.6mm. They could be thinner, but metal working becomes more difficult.

I have used very basic tools, circular cutters, drills and files. Safety is a concern with working on small brass items (fingers/eyes) so I have always used contact glue to fix brass on thin plywood and saw and drill both at the same time, You work from the center outwards.

A hemi-spherical file is perfect to put a chamfered edge on the hole.

Modern velvet doesn't cut well - you would be better advised to use buy some black velvet ribbon, which is an item which is still available very easily.

[dustspots]

What great tips Steven! I would never have thought of gluing the brass to plywood before working it, nor using velvet ribbon instead of velvet fabric! Obviously I'm not as practical as I thought I was... but am quickly learning through your expert help... Thank you!!! I'd like to try and keep within original washer thickness tolerances if possible, so I'll try to find a metal merchant who sells brass sheet of 0.6mm thickness in the city, if I can't, I'll have to use the 1mm I already have available and then gently chamfer the "hole" down to approximately 0.3mm from one side.

Thanks again!

[Steven Tribe]

Let me know the internal diameter (my guess is 5.4cm - the size of the meniscus no.2!) and I'll send you some suitable scrap brass which is already 0.6mm.

[dustspots]

Great guess Steven! You're correct the internal diameter is 5.4cm! Thank you for your very kind offer of sending some 0.06mm brass... but I won't need to trouble you for it as a friend of mine who is a sculptor has some spare pieces and will drop them off to me next week!

In the meantime I'd like to remove some internal dust sitting behind the limiting "hole" but cannot get access because the flange is a little corroded and has seized to the barrel... what do you suggest the best way to gently remove the corrosion and separate the barrel from the flange might be? Thank you!

Thanks again for your help!!!

[Steven Tribe]

Dallmeyer was one of the companies which went in for standardisation as much as possible! They even made Waterhouse stops which could fit a whole series of very different products, like large RR's and Portrait Petzvals.

You should keep your eyes open for a scrap no. 2 landscape meniscus (that is, without lens!), as the front section with iris will screw directly into yours.

Note that the maximum aperture for these lenses starts at about F16.

I have found that screwing the flange onto a 1 foot piece of wood, using at least 2 of the holes, can create quite a torque (both continuous or with sharp blows from a mallet/hammer). Of course, plenty of penetration oil first!

I include a photo of my no. 2 meniscus (patent) which shows the detachable iris/lens hood section.