Dallmeyer Triple Achromatic Lens F3.5 Question

[rossn4]

Hi, I have a large brass Dallmeyer Triple Achromatic Lens and was hoping someone would be able to tell me more information about it. All the pictures and info I could find on the Triple Achromatic Lens says that they were an F10 lens but this one is a F3.5. It has a focal length of 11.5 inches and the glass diameter is 3.3 inches which comes out to about f3.5. The front lens group goes deep into the lens body and looks to hold both the front and middle lens groups. Looking at the Vade Mecum I do see a description of a f4 Group Lens which they say is a faster version of the Triple Achromatic. This lens is f3.5 but could this be another version of that lens? Another interesting thing about the lens is there is no serial number on the barrel. If anyone could shed some light I always enjoy a lens mystery being solved. Thanks.
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[roetronxoay]

very interesting lens. Please share some images when you can

[Steven Tribe]

No Way this is a Lens which can be used at F.3.5.
Look at the range on the Aperture scale - doesN ‘t look right does it?
Universal use of The modern F scale came after 1900.
Search for Old aperture scale.

[rossn4]

The f stop goes 3.5, 4.5, 6.3, 9, 12.5, 18. The lens probably was made post 1900. The scale looks similar to some Stigmatic lenses I see which were in the post 1900 years. I can take some test 8x10 pictures and will post them when I do.

[lucaas]

The aperture diaphragm of Triple Achromatic lens comes between the first and second lens group. Have you checked the three lens groups are all 2 elements cemented?

[rossn4]

I took some images with the lens for those who are interested. Here are 3 pictures with the diaphragm set at f3.5, at f6.3, and at f18. I took the pictures on 8x10 photographic paper (Aristo MC RC) and then scanned and inverted the images. Since I'm stuck in the house like everyone else I shot out the window at the building across my street. They are not the best photos with fingerprints and streaks on the photos but I'm without a darkroom.

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[roetronxoay]

exposure seems close enough to be certain it's indeed a 3.5 lens. Slight vingette on 8x10 though, so it's a cabinet lens?

[rossn4]

I used a packard shutter a couple inches inside the camera. It caused some vignetting on several of the lenses I tested out.

[roetronxoay]

now some portrait test please :p