Need some help with this hermagis

[alex from holland]

Hi all,

Today i "found" this lens.
I bought it from a belgium photographer. His dad (who was also a photogrpaher) bought it new !
As you can see it says hermagis paris Eidoscope 4.5 no 1
Now it becomes weird.
A nr 1 should have had a focal lenght of about 19 inches and w width of 3.8 inches.
This one has a focal lenght of about 28 inches and has a width of 5 inches.

These numbers come much closer to a hermagis eidoscope no 0

anyone has an idea ??

alex

[Mark Sawyer]

Check whether the inner diameter of the barrel at the aperture location (measured through the front element) is really the f/4.5 the engraving indicates it should be. If a19" lens, it should be about 4.25". If a 28" lens, it should be about 6.25".

You may be missing a positive element somewhere, which would increase the focal length.

Mind you, I know very little about Eidoscopes, and we have some experts here who will surely chime in, so if nothing else, this is a gratuitous bump!

[8x10 user]

Yeah, it has got to be missing an element IMO.

[Steven Tribe]

Not possible to be missing an element as the design approaches that of an RR - 2 (1+1). I think this another sign of L'eidoscope changing sizes for selected numbers at various stages in its long production. The 0 must surely have an addition at some stage! Just like Goertz and Dallmeyer introduced 0 and 00 for new smaller sized objective when small cameras became popular (at the other end of the scale!).

[alex from holland]

I found this page (thanks to sven schroder !)
It turns out to be a no. 0
On that page a no 0 claims to have a focallenght of 63.5 cm which is 25 inch.
I remeasured it with a good light and i measure about 65 cm
Also the diameter is 12 cm 4.5 inch is almost the same.

So i think they must have made a mistake with the engraving....
Mystery solved ??

[Mark Sawyer]

A 25" lens needs just over a 5.5" diameter at the aperture (measured through the front elements) to be an f/4.5 lens. They would have had to have erred on the barrel and the aperture ring engravings. Your metric measurements make it an f/5.3, while the English make it an f/5.55

Not possible to be missing an element as the design approaches that of an RR - 2 (1+1)...

Not knowing much about the Eidoscopes myself, can anyone comment on how the softness-inducing aberrations are induced? Spacing, perhaps?

[alex from holland]

i just saw the the page i have posted is for the older f 5 lenses.
So maybe they have changed the numbers and the no 1 is correct on my lens ??

I still measure ABOUT 25 ich (measured into a light, from the aparture blade to a "clean and sharp" pricture on a white sheet.
I know this isn't a scientific measurement. I will try to measure at infinity tomorrow (it's dark over here now....)

The aparture ring say's 4.5 up to 20.

alex

[Steven Tribe]

There is no soft adjustment (moved lens components etc) - apart from the F selection. Stopping down produces a sharp image. It is, unfortunately, not an objective I have had in my hands. While this size 0 (old 1?) is a wonderful piece of optical design - I find it difficult to imagine it in photographic use to-day.

[8x10 user]

Measured from the out side of the barrel, the diameter of the 19" F/4.5 is ~4&5/8" while a 24" F/5 is ~5&3/8".

A 24" stands almost foot tall including the lens shade while a 19" is ~ 9 1/2" tall.

If you take one of the two groups of elements off you will get a longer focal length, but now that I think about it the resulting focal length would probably be a lot longer then 25 inches.

I hope this helps.

Ed

[walter23]

Also the diameter is 12 cm 4.5 inch is almost the same.

Yeah, I don't know if you noticed it, but the diameter listed in that brochure is 125mm (12.5 cm) or 4.9", so you're probably correct that it's an earlier, or mislabelled, no. 0.