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Mark Sawyer
12-Jul-2004, 23:12
I recently bought a 75mm Goerz Hypergon ($1200 with a camera, for those keeping track of the going rate), and have some questions about it...

How freely should the fan spin? Mine spins a little with each puff from the bulb, probably enough to work fine, but should it spin really freely? Should I lube it with wet or dry silicon?

Would a more modern center density filter work effectively? Say, something made for a metrogon? Or would using one made for a different lens likely cause rings of lightness/darkness because they have different fall-off rates?

It came with a very nice 8x10 Seneca Improved View Camera. The Seneca is very light (7 pounds, as opposed to 12.5 for my Kodak 2d and 11 for my custom mesquite 8x10). The bag bellows has a maximum (no, not minimum, I mean maximum!) extension of 4.5 inches, and looks like it could be factory installed. Does anyone know whether Seneca produced this as a wide-angle version, possibly just for the hypergon? (How many other lenses could there be for a 4.5 inch bellows?) Or did someone just do a really nice conversion?

Any other advice for using this lens would be much appreciated. (At last I can start thinking of my 6 1/4 inch Wollensak as a telephoto...)

- Mark Sawyer, Tucson, AZ
Emmanuel BIGLER
13-Jul-2004, 04:59
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Mark

Congratulations for the purchase of a vintage Hypergon.

here is a summary of the Hypergon family


f N1 -> N2 image circle total coverga
Goerz Hypergon 60 f/22 f/45 330 mm 140 &deg;
Goerz Hypergon 75 f/22 f/45 412 mm 140 &deg;
Goerz Hypergon 90 f/22 f/45 495 mm 140 &deg;
Goerz Hypergon 120 f/22 f/45 659 mm 140 &deg;
Goerz Hypergon 150 f/22 f/45 824 mm 140 &deg;
Goerz Hypergon 200 f/22 f/45 1099 mm 140 &deg;


The "fan-filter" device in itself is an absolute incentive to get such a lens ;-)

We had a discussion on the French MF/LF forum recently about the design and performance of the Hypergon. One of the contributors of the French forum is a professional lens designer and he ran a design software on the Hypergon design.

http://www.galerie-photo.info/forum/read.php?f=1&i=26896&t=26896

The conclusions are that the lens obeys, unfortunately, the classical cos^4(theta) fall-off rule, whereas more modern wide angle view camera lens designs somewhat compensate for this due to pupillar distorsion.

The consequence of this are that if you wish to use the full 140 degrees of angle, be prepared to an extreme loss of light in the corners. At 140 degrees (i.e. 70 degrees off-axis), the amount of light is less than 2% with respect to the on-axis field. i.e. 5 to 6 f-stops !! cos(70)= .34, ^4 = 1.3% !!

Now if you are more reasonable and limit to +-60 degrees, the light fall-off is less dramatic, cos(60) = 0.5, ^4 =6.25%... 4 f-stops.

So if you use a concentric compensating filter you will partially compensate but not totally, they are designed for, say, a cos^3 law or something. It might be interesting to borrow such an expensive filter just to check for the results. The other approach, (but do not tell it to filter vendors ;-)), would be, if you are digitally-inclined, to compensate by digital image processing afterwards ! a pure 1/cos^4 theta law to implement! a pure acamedic exercise ! ;-);-);-)

Another conclusion is that off axis at the maximum angle the effective numerical aperture is so poor that diffraction effects are immense, yielding a FTM limit of about 5 cycles / mm (whatever the focal length might be, the effective f-stop in the corners is the same for all hypergons, hence the same diffraction limit).

Now, do me a favor, DO FORGET ALL THIS THEORY and be happy with your Hypergon ; I wish I could have one handy !! ;-);-)

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Ernest Purdum
13-Jul-2004, 08:25
Congratulations on a most interesting acquisition.



I don't think any harm could be done by trying a lubricant. One of the penetrant type might be the best, since cleaning is likely needed as much as lubrication.



Regarding your bellows, I have never seen any mention of a bag bellows from the time period of your Seneca, so my guess is that it is a later replacement, but quite possibly for an earlier bellows which was also very short but of more traditional construction. The clue would be the length of your rail, I think. If the factory had provided a short bellows, the rail would be expected to be correspondingly short.



The only camera I know of which was designed to take advantage of the Hypergon's coverage was the Folmer & Schwing Skyscraper Special. This did indeed have a very short rail, but with pleated bellows. Here is what F&S said about the bellows. "The bellows is rectangular and wedge shaped, tapering gradually from the side to the large front board frame, insuring strength and preventing bellows from sagging. The bellows is made from a high grade material specially prepared for it."



I think it is very unlikely that you could find a center filter with at all the needed correction.



I have a Hypergon also, but mine is a peculiar item made by Fuji. It is in a sleeve mounting without any means of compensating for fall-off. I have to figure out some sort of collet in order to mount it.



I hope that you will let us know how things are going as you experiment with this most interesting lens.
Alex Woronow
5-Sep-2004, 10:01
I have a 60mm hypergon that I built a fixed-focus-no movements 8x10 camera for. Yes, it covers 8x10 easily. The depth of field is great. From about 2 feet or so to infinity. My star filter also spins just while air is applied. I suspect this is normal--not much mass, therefore not much momentum. I just pump the bulb a few times. I've been reluctant to lub it. Maybe take it to a professional and ask an opinion. Certainly dismount the star before doing anything. There are three screws, only the two outermost need to be removed.

I've started a project to mount a center filter on my camera. I got an old Metrogon filter (not the 6" Metro.--filter too small I think--I got the 12"). The red center filter should also sharpen the image if there really is an color abberation to worry about.

I measured and drafted the lens, and if you look at the lens, the 140deg coververage on the front reaches just above the lip that runs around the lens (same from the spread of the image from the back).

Enjoy...I sure do.