Rodenstock IMAGON questions

Samuel Hotton · Oct 3, 2008

First question: I have a Rodenstock Imagon 250mm lens in a Copal #3 shutter that I purchased NEW in 1981. The three aperture discs that came with mine are all marked f=200. I JUST noticed this! Should it not be f=250 as I have a 250mm lens, NOT a 200mm lens. Did the factory put the wrong discs in my box, OR do they use the same aperture discs for both 200mm and 250mm lenses?
IF someone out there has a Imagon 250mm lens, would you please look on your aperture discs and see if it reads f= 200 or f=250.

Second question: Why are the apertures marked as H= 5.8, 7.7, 9.5, 11.5 Even the lens is marked H=5.8?? These H numbers are NOT equal to f numbers! One will over expose your film IF you use the H number on your light meter. Does ANYONE know the history or meaning of H numbers??

With thanks,
Sam H.

Philippe-Georges · Oct 3, 2008

I had a Imagon 250 mm for 15 years till it got stolen about 5 years ago, what made me very, very, sad indeed.
I can not recall whether ore not the f number was engraved on the discs, but if the H number of the 'clearest' disc is the same as the H number on the lens, then I think that the set of discs might be the same for a 200 mm and a 250 mm lens, who knows,
The 'H' is coming from the German 'HELLIGHEIT', meaning 'clearness brightness' and, in this case, the amount of light that is available to expose the film when the disc is mounted and opened ore closed (and all the steps between that). These discs are no real apertures, the centre hole, which is not changing when turning the disc's ring, is perhaps somewhat like an aperture, but the little holes around it are regulating the amount of optic (spheric-) aberrations and also the transmission of light. One might not forget that a so called 'soft' image is more brighter than a rather 'normal-to-hard' image. A soft image 'contains' more light and, by this, is exposing the film whit that typical amount of light.
The Imagon whit out a disc is far more softer, thus more brighter (hell), than an other lens of the same focal length and diameter (opening).
So, each disc has a fixed pseudo aperture and a very own amount of light transmission via the perepheric holes. This is why each disc, and the lens not having an aperture only a diameter and typical (aberrated) light coming through (!), is considered to have a HELLIGHET (brightness) and not a F number.
You will see that, when the disc with the highest H value is mounted and closed, there is far less light 'coming through' than compared to a normal working lens with a normal aperture system and closed to the same amount, if you understand what I mean.
Helligheit has to do with the (artistic?) effect of the amount of light, and aperture with the mathematic amount of light (energy), reaching the film.

I hope, dear Samuel, that my pidgin English was clear (bright) enough, so that you could understand all what was to do about 'H'.

Good luck whit that marvellous lens,

Philippe

AgX · Oct 3, 2008

But as both lenses have got the same nominal aperture, the 250mm lens will have a larger front lens diameter. And, especially as the the circumference of the the aperture discs is essential for controlling off-center rays, by making use of an spheric aberration, how can both sets of discs have the same diameter?

Philippe-Georges · Oct 3, 2008

Dear Agx,

Good question!
As an answer I did a quick scan of the Rodenstock brochure of 1989. As you can see in the attachment, the 200 mm and the 250 mm have the same HELLIGHEIT.
Do not ask me for an explication...

Philippe

AgX · Oct 3, 2008

As a wild guess:
200 to 250 is not that much of a difference. As to be expected it was done concerning the image circle.
I thus would take those maximum aperture statements for the unobtruded lens with a grain of salt. So I guess both versions got the same mount for the disc and the same discs.

But perhaps someone has got both versions and the accompanying discs and can tell us more.

But nevertheless those H values on the discs should give the same effect concerning exposure as a regular iris-diaphragm with the same value.

raucousimages · Oct 3, 2008

You have the wrong discs. I have an Imagon 250 made in the mid 90s and it has discs marked H-250. With the correct discs the H value is very close to the corosponding F stop in exposure, there should be little or no over/under exposure.

My favorite way to use the lens is to get the proper F-stop tape from Copal for a 250mm lens, install it on the shutter (you will get 2 tapes and 4 screws) and just use it without the discs. Use the f-stops instead. Exposure is dead on and you can vary softness and DOF with ease.

Chazzy · Oct 4, 2008

raucousimages said:
You have the wrong discs. I have an Imagon 250 made in the mid 90s and it has discs marked H-250. With the correct discs the H value is very close to the corosponding F stop in exposure, there should be little or no over/under exposure.

Are they equivalent with the little holes open or closed?

Philippe-Georges · Oct 4, 2008

raucousimages said:
You have the wrong discs. I have an Imagon 250 made in the mid 90s and it has discs marked H-250.

I think it duos not matter that much, but it matters.
The peripheral holes are used to control the aberrations rather than the amount of light. And aberrations is all that matters with this lens.
This is, perhaps, why there was a ND 4 filter added to the set.
The centre hole of the three discs is more to control, step by step, the aberration and the little holes to control this variously. The aberrations are a little more present in the border than the centre of the image circle.
The higher the 'H' value the higher the so called relative sharpness (= lesser aberrations), and till a certain amount the depth of field. When the disc with the smallest hole is mounted and closed, the Imagon can produce almost 'normal' images.
The discs are marked from H 5,8 to H 11,5, and so on, not just one number. This is why the discs are numbered in H values rather than in F values. And if the H values happen to correspond to F values, then this is only when full open ore - closed.
Originally, the Imagon was mounted in a shutter whit out an Iris.

Do not consider the Imagon, a (soft-focus-) achromat, as a common lens. It was not designed as such by Rodenstock, as a matter of fact they called it a 'Weichzeigner'.

Philippe

raucousimages · Oct 4, 2008

I wonder if the differences in the H200 discs and the H250 discs is the size of the holes. That would efect the exposure also. I have the 250mm and the H250 discs. I use the following H to F conversion with good results.

H11.5=f11.5
H9.5=f8 3/4
H7.7=f5.6 2/3
H5.8=f5.6 1/6

But as I said before my favorite way to use it is by adding the f-stop tapes to the shutter and just use the f-stops.

Dave_B · Oct 4, 2008

I have a 250mm Imagon and the disks with it are labeled f=250 and then the range of H numbers.
Cheers,
Dave b.

Samuel Hotton · Oct 7, 2008

Thanks to all for checking the "H" plate numbers for me. Thanks for the H definition, that is most interesting, I shall research this more.
It appears as though someone put the WRONG plates in my box.
QUESTION: Is Rodenstock still in business producing this lens?? Any ideas where I might purchase the proper H-250 discs/plates??? New OR used.
I've just measured the SHARP aperture WITHOUT the side holes open, here are the results.
H=11.5 14.68mm diameter focal length divided by aperture = f stop
250mm divided by 14.68mm = f 17

H=9.5 17.68mm diameter 250mm divided by 17.68mm = f 14

H=7.7 21.48mm diameter 250mm divided by 21.48mm = f 11.6

The calculated F stop is about 1 1/4 stops LESS than the marked H stop.

I do find that in actual practice using FILM, the following f stops work well.
H=11.5 is f14
H= 9.5 is f 12
H=7.7 is f10

SO, in actual "real world" exposures using camera and film, I'm losing 3/4 stop of light with these H=200 aperture plates and not really seeing the designed beauty that this lens is truly capable. I'm bummed out! I NEED the proper plates!

Sam H.

raucousimages · Oct 7, 2008

Try KEH. Might be a long shot but worth a try.

AgX · Oct 7, 2008

Samuel,

Rodenstock has been taken over in 2000 by a greater optical holding, Linos.

However the brand name still exists as well as many of their lenses, but not the Imagon. However they still have a friendly technical service.

see also:

http://www.linos.com/pages/home/shop-optik/rodenstock-foto-objektive/analoge-fachfotografie/

Philippe Grunchec · Jul 31, 2009

I just got a 5,8/250 Imagon on Compound!

Philippe, I like very much your B&W images: do you develop your Imagon negatives in a special brew, as recommended by Heinrich Kühn (I think)?
BTW, HelligKeit!

Philippe Grunchec · Aug 1, 2009

Would old (seasoned) D-23 do the job? What about Pyrocat HD?

Philippe-Georges · Aug 4, 2009

Dear Philippe,

Actually, the Imagon made pictures ware all shot on APX whether 100 ASA or 400 ASA and developed in Rodinal 1+50.
My Imagon got stolen before the demise of AGFA-PHOTO. Now I work on Tri-X, EI 400 ASA, processed in Pyrocat-HD and eventually push develop the Tri-X at 1000 ASA in GAFA's Refinal concentrated and replenish. I still have a nice stock of this developer, just enough till the end of my days...
Refinal is AGFA's interpretation of D-76.
When I feel a sudden need not to process in a staining developer, I develop in PC-TEA. Right now, I am tempted by the Caffenol process, just to satisfy my curiosity, perhaps I will use it for paper.

As I never got a Imagon since, all my more recent work is shot with Hasselblad, a lot with the S-Planar full open. For the 1:1 macro work, I sometimes put the S-Planar on my 4"x5" Linhof, this works very well indeed, and I do not need that long bellows extension. You see, a lot of my subjects are about as large as 10 cm high, this fits perfectly on a 4" x 5" sheet.

Philippe

Willie Jan · Aug 4, 2009

i saw two imagon brochures at http://www.cameraeccentric.com/info.html.

why not contacting rodenstock directly. They are very friendly. I had a problem with a lens and they checked it for free!

Sirius Glass · Nov 19, 2011

raucousimages said:
Try KEH. Might be a long shot but worth a try.

KEH occasionally has the discs. They have the 250mm H7.7/H9.5 presently.

Unlike the sharp lenses that we are used to, the manufacturer's recommended focusing method is:

With the lens outside holes closed, extend the lens out beyond the focusing range.
Bring the lens in until the closest part of the subject is in focus.
Continue to bring the lens in until the furthest part is in focus.
Bring the lens back to have the whole subject in focus.
With the little holes closed the subject is sharp; with holes open the softness is added.

Steve

Two23 · Nov 19, 2011

I have an Imagon 250mm with all three disks. I don't have the instruction manual though. Mine has the Copal 3 shutter. Exactly where can I get that "tape" that has apertures printed on it?

Kent in SD

Sirius Glass · Nov 20, 2011

The disk with the smallest holes is the H9.5/H11.5.
The disk with the middle sized holes is the H7.7/H9.5.
The disk with the smallest holes is the H5.8/H7.7.

Check your email for the instructions that I have.

Steve

Vanishing Point Ent. · Nov 20, 2011

You have the wrong discs. Would you like to sell your 200 mm Discs ?

raucousimages said:
You have the wrong discs.
I have an Imagon 250 made in the mid 90s and it has discs marked H-250.

I recently got an eBay deal for a Rodenstock 200 mm Imagon lens.
However, it only came with 1 disc. I would love to have the other
discs, as well as the B&W yellow green filter that comes with it.

Would you be willing to sell your " wrong " discs ?
You might be able to find the " right " discs, on eBay. I've seen them offered.
Please let me know, my E-Mail is fgk_vpe@yahoo.com Please let me know, Yes, or no.

Sirius Glass · Nov 20, 2011

Shucks, I am looking for H5.8/H7.7 250mm disk, 250mm hood and ND4 slip-in filter. Any sellers out there?

Steve

Rodenstock IMAGON questions

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