PDA

View Full Version : Need some help with this hermagis



alex from holland
22-Jan-2010, 10:48
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


http://upload.pbase.com/image/121309607/original.jpg

http://www.pbase.com/alex28/image/121309608/original.jpg

Mark Sawyer
22-Jan-2010, 13:52
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
22-Jan-2010, 14:06
Yeah, it has got to be missing an element IMO.

Steven Tribe
22-Jan-2010, 14:54
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
22-Jan-2010, 14:56
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 ??

http://upload.pbase.com/image/121314151/original.jpg

Mark Sawyer
22-Jan-2010, 15:10
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
22-Jan-2010, 15:25
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
22-Jan-2010, 15:32
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
22-Jan-2010, 15:47
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
23-Jan-2010, 14:29
Also the diameter is 12 cm 4.5 inch is almost the same.

http://upload.pbase.com/image/121314151/original.jpg

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.

alex from holland
23-Jan-2010, 14:39
Hi walter,

yes i did, but the page i posted is mentioned for the older series f 5.0
The newer series are f 4.5. Maybe they have also changed the numbering.

alex

alex from holland
23-Jan-2010, 14:50
I just focused at infinity and it turns out to have a focallenght of about 19,5 inch (about 48 cm)
In that case the no 1 is correct, but to achieve the f 4.5 instead of the f5 they increased the lens width to aprox 4 5/8 inch
So Ed was correct !!

Thanks

alex

Jim Galli
23-Jan-2010, 15:01
Sweet lens. You are a lucky fellow.