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Thread: Fresnell lens

  1. #11

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    Dear Bobwysiwyg, if you like to do it right way, just follow my instructions as it shown above. I have a ShenHao and I used to install Fresnel on this camera few times. If you have a Fresnel directly made for the Shen Hao you will be ok. The kind of problems as Dan Fromm mention above may happens if the camera not disigned for the Fresnel at all, ore if the fickness of the Fresnel lens are bigger than required for that particular camera. But as i said above, Shen Hao has a spot for the fresnel and camera designed for the fresnel, they just sell it separatelly as an option, and if yours Fresnel made directly for the ShenHao the lens will fit in its spot with out affecting the ground glass position. This is the right way to go.
    Thanks.
    Last edited by Rudolf Karachun; 04-17-2013 at 12:02 PM. Click to view previous post history.

  2. #12

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    Quote Originally Posted by BrianShaw View Post
    I'd stop right now and dial the phone (if ViewCamera Store has a phone number) if I were you. What you read on ViewCamera store can be read etiehr way. If the focus panel was designed with a recess for fresnel under the GG then it seems like Rudolf could be right. If not, then Dan could be right.
    And AGx is right, too. A Fresnel is optically about 2/3 it's physical thickness. I do not use a Fresnel on either of my view cameras for this and other reasons.

  3. #13

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    Only a malicious SOB would deliver a focusing panel designed for a fresnel without the fresnel. If the focusing panel is designed for a fresnel and the fresnel isn't there, the ground glass will be out of register with the film plane.

    Rudolf, you can't have it both ways. Either the OP was screwed when it bought its camera or it was screwed when it bought its fresnel.

    I learned all this the hard way. I shoot Pacemaker Graphics with Graflok backs. When the Graflok back was introduced the fresnel was optional; when installed it was mounted in front of the ground glass. Graflok focusing panels (from Graflex Inc.) made to use a fresnel and those made to be used without a fresnel have the same casting numbers. In both types, the ground glass rides on bosses; the bosses in focusing panels modified to use a fresnel are milled down to keep the ground glass in register with the film plane.

    Guess who put an aftermarket fresnel in front of a Graphic's GG? Interestingly, the instructions that came with the fresnel said to mount it in front of (on the lens side of) the ground glass.

    By the way, at one time a chinese view camera -- I thought 4x5 Chamonix, not Shen Hao -- was routinely delivered with the ground glass out of register with the film plane. Stupid design error that was eventually corrected after many complaints from buyers.

  4. #14
    bobwysiwyg's Avatar
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    Perhaps I will give them a call. I currently have a Shen Hao 4x5 which I've had for a few years. I did installed a Fresnel (not specific to the camera) about two years ago and liked the fact that it brightened things up quite a bit. At my age, every little bit helps. Current mounting arrangement is original GG set in the recess with the GG surface facing the lens. The Fresnel is then placed on top of that with the concentric surface facing the smooth side of the GG. I just removed both to examine the recess again. I see nothing that would accommodate putting the Fresnel between the GG and the lens without moving the focus point/film plain. So, barring any additional information I get from a phone call, it seems to me the current order and arrangement is how it would have to be on my Shen Hao. Perhaps later modes were designed differently to accommodate the Fresnel in front of the GG?
    WYSIWYG - At least that's my goal.

    Portfolio-http://apug.org/forums/portfolios.php?u=25518

  5. #15

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    Dear Dan, I'm sure you probably learned and know much more than me. But I just know my camera, and it happens to be a Shen-Hao, and I know how it was designed. Maybe you right about the manufacturer, how designed the camera with Fresnel and sells it as an option, but I'm not a manufacturer, I'm a user and I have to follow manufacturer. And if manufacturer wants me to pay more for the Fresnel, I pay more, because I want to have Fresnel on my camera. The question was about how to install Fresnel on the Shen-Hao, and I gave the detailed answer, and even more, gave some explanations to the others why it is this way and not the other because the camera has a place where the Fresnel shall go. I don’t see that anybody except me gave the same detailed answer or even mention that he knows that particular camera and how it’s made. I did best what I can. All other posts in that treat are just about general camera design and construction and knowledge of all of us. And we all are right, we all know that the ground glass shall not to be moved if we like to have a sharp pictures. And believe me or not it will not be moved, because the Shen-Hao designed this way. To follow my recommendation or not this is another question and let the person why ask the question decided. I just did my best. Thank you.

  6. #16

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    Rudolf, if the fresnel must be present and mounted in front of the GG then its absence is a problem. The GG can't be in register with the film plane with the fresnel in front of the GG and without a fresnel.

  7. #17

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    Quote Originally Posted by E. von Hoegh View Post
    And AGx is right, too. A Fresnel is optically about 2/3 it's physical thickness. I do not use a Fresnel on either of my view cameras for this and other reasons.
    Yes, I don't like them either. Tried one on a view camera but didn't like it one bit. No real advantage and seemed to make viewing GG with loupe more difficult. I only use on on a Graphic which was originally designed and delivered with one... and that is mostly because, due to the design of that camera's back, if I remove it my GG will be out of register with the film plane.

  8. #18

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    Ok. Let me be more detailed. Usually the wooden frame where the ground glass go, has shoulders from four sides on which the ground glass slipping. The Shen-Hao designed the way that just two shoulders from two opposite sides of the frame supporting the ground glass. The other two shoulders from other two opposite sides of the wooden frame a made dipper, and there is a gap approximately 2mm. between the shoulder and the ground glass. These two shoulders made dipper in purpose to support the Fresnel. The Fresnel itself, if it is made especially for the Shen –Hao has fickness and cut to the size to slip on these two deeper shoulders, and not on the other two witch supporting the ground glass. This way when the Fresnel inserted, the ground glass stays on the same position as without Fresnel.

  9. #19
    Ian Grant's Avatar
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    There's two separate issue here. Some backs have a recess under the ground glass for a fresnel this means the fresnel itself doesn't alter the position of the glass, any shift in focus is relative to the depth of the fresnel rings rather than the overall thickness of the fresnel. There may need to be a thin shim when no fresnel is used.

    However where a fresnnel moves the ground glass in a back not designed for a fresnel then the focus is altered and as Dan says in that case the fresnel should be on the rear of the Groundglass - pohotographer side. Where a back is designed to have a fresnle sandwiched on the inside of a fresnel (no specific recess) then when the fresnel is removed there needs to be quite a thick shim a touich less than the fresnels thickness.

    Ian

  10. #20

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    Quote Originally Posted by BrianShaw View Post
    Yes, I don't like them either. Tried one on a view camera but didn't like it one bit. No real advantage and seemed to make viewing GG with loupe more difficult. I only use on on a Graphic which was originally designed and delivered with one... and that is mostly because, due to the design of that camera's back, if I remove it my GG will be out of register with the film plane.
    My first LF camera was my Linhof STIV, which came with a Linhof Super Screen installed. The original GG was in the Super Screen box. I hadn't even made any photos with it before I removed the %&$@* Super Screen, gave it away, and replaced the original GG. It hasn't moved since.

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