Ok here is a working link I hope:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7609665834&rd=1&sspagename=STRK:MEWN:IT&rd=1
item number: 7609665834
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7609665834&rd=1&sspagename=STRK:MEWN:IT&rd=1
item number: 7609665834
not a great lens
That Gerogon is not a process lens, it is a very good color-corrected enlarger lens. It has a focal length of 360 mm and a maximum f-stop of f9. That means the clear aperature is only 360/9 = 40 mm. You see how the middle of the lens is much smaller than the outer lenses? You may have a difficult time getting much light through this lens. (That does not matter for an enlarger, since you can just increase the exposure time.) You will have to use a brightview LCD, or an LCD that you can remove the antiglare layer. Then adjust the fresnel distances perfectly to get the arc image right at the center of the lens.
The Rodenstock website I have used to look up lens data does not have the Gerogon. I think it is obsolete.
http://www.prograf.ru/rodenstock/largeformat_en.html
So I don't know the maximum angle of coverage for this lens. But I think the chances are good that it will cover a 17" LCD. I bet it could cover a an 11" by 14" print from an 8" by 10" negative. You can use the usual equations to calculate the distances to do that, and then determine the angles to the corners of both. Do the same calculation for a projector and see if the required angles are the same or less.
In summary, I think you will get a perfectly-focussed image from corner to corner but you will have to work very hard to get it bright. Let us know how it works out.
That Gerogon is not a process lens, it is a very good color-corrected enlarger lens. It has a focal length of 360 mm and a maximum f-stop of f9. That means the clear aperature is only 360/9 = 40 mm. You see how the middle of the lens is much smaller than the outer lenses? You may have a difficult time getting much light through this lens. (That does not matter for an enlarger, since you can just increase the exposure time.) You will have to use a brightview LCD, or an LCD that you can remove the antiglare layer. Then adjust the fresnel distances perfectly to get the arc image right at the center of the lens.
The Rodenstock website I have used to look up lens data does not have the Gerogon. I think it is obsolete.
http://www.prograf.ru/rodenstock/largeformat_en.html
So I don't know the maximum angle of coverage for this lens. But I think the chances are good that it will cover a 17" LCD. I bet it could cover a an 11" by 14" print from an 8" by 10" negative. You can use the usual equations to calculate the distances to do that, and then determine the angles to the corners of both. Do the same calculation for a projector and see if the required angles are the same or less.
In summary, I think you will get a perfectly-focussed image from corner to corner but you will have to work very hard to get it bright. Let us know how it works out.
The seller told me the clear glass aperture inside the capture ring is 60mm. Another words with the aperture wide open at f/9 there is 60mm diameter glass that is clear to allow light to pass through. So are you saying if you had a 360mm FL lens with a 2.8 max aperture you would have a 128mm diameter ?
The "clear aperture" may be very different from the diameter of either of the outer lenses. Lenses that have an adjustable aperture (like this one) usually put it right in the middle. Decreasing the size of the aperture makes it focus sharper and also makes the amount of light getting to different areas of the film more even. But it does that by blocking the extra light that would have fallen in the center of the image.
Like I said, that is fine for photography because you can just increase the exposure time. Not useful for projection, unless you think your screen image is too bright!
Anyway, "clear aperature" is always focal length/f-stop. The internal light path may be physically larger or smaller than that, but the light path can be converged or diverged by the outer lenses before it gets to the most narrow opening inside the lens. The f-stop numbers take that into account, so you can use any lens with the same focal length and f-stop setting and you will get the same amount of light to the center of the film.
Like I said, that is fine for photography because you can just increase the exposure time. Not useful for projection, unless you think your screen image is too bright!
Anyway, "clear aperature" is always focal length/f-stop. The internal light path may be physically larger or smaller than that, but the light path can be converged or diverged by the outer lenses before it gets to the most narrow opening inside the lens. The f-stop numbers take that into account, so you can use any lens with the same focal length and f-stop setting and you will get the same amount of light to the center of the film.
damn so sounds like i have to desist and eat a negative feedback. Am I blocked for buying temporarily when getting a negative feedback as a buyer?
No, you don't get blocked, but the seller can post exactly why he gave you the negative feedback. You then get to post a reply to that. Some sellers then may choose to reject your bids, but that is not automatic. If you can come up with an adequate excuse, and have lots of positive feedback to balance it out, then eventually the sellers will "forgive" you.
If you do fail to buy the item that you bid for, then you will cause the seller a loss in the amount he spent for the auction as well as his time to create the auction posting. I suggest that you go ahead and buy the lens so you can give it a try. You might be very happy with it. It will certainly give you a very sharp image. We just don't know how bright or how wide the object field will be. The only way to find out is to try it!
If you later decide you want to go with a different lens, you can sell it on eBay. So you will not get stuck with it.
If you do fail to buy the item that you bid for, then you will cause the seller a loss in the amount he spent for the auction as well as his time to create the auction posting. I suggest that you go ahead and buy the lens so you can give it a try. You might be very happy with it. It will certainly give you a very sharp image. We just don't know how bright or how wide the object field will be. The only way to find out is to try it!
If you later decide you want to go with a different lens, you can sell it on eBay. So you will not get stuck with it.
An honest option to get out of the sale
If you don't want negative feedback, or the lens, then I'd suggest contacting the buyer, explaining that you made a mistake and the lens wasn't what you needed and (This is the most important part) offer to cover his ebay costs. Your loss for a lens you don't need should be quite a bit less, his/her unfair loss to eBay will be nonexistant, and you'll not receive negative feedback. If (s)he doesn't like that idea of course, you should then still complete the transaction. (And of course, leave positive feedback for him/her. Be it for shipping you the lens, or accepting a consolation payment). Even if you do have to buy the lens, you could always just turn right around and sell it on eBay yourself.
If you don't want negative feedback, or the lens, then I'd suggest contacting the buyer, explaining that you made a mistake and the lens wasn't what you needed and (This is the most important part) offer to cover his ebay costs. Your loss for a lens you don't need should be quite a bit less, his/her unfair loss to eBay will be nonexistant, and you'll not receive negative feedback. If (s)he doesn't like that idea of course, you should then still complete the transaction. (And of course, leave positive feedback for him/her. Be it for shipping you the lens, or accepting a consolation payment). Even if you do have to buy the lens, you could always just turn right around and sell it on eBay yourself.
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