Vignette on Linhof 4x5 reflex finder

[ghoonk]

I've recently acquired a Linhof reflex finder for my Kardan and Super Technika and noticed a strong vignette while focusing.

I understand that the vignette won't show up in the final image but this interferes with composition and focus and I was wondering why this doesn't happen on the ground glass, and more importantly, how do I circumvent this?

[Bob Salomon]

To use the reflex you must have a Fresnel installed. Do you?

[ghoonk]

Yes, I have the fresnel installed

[Bob Salomon]

Yes, I have the fresnel installed

Do you know which Linhof ground glass and Fresnel you have?

[ghoonk]

Good question - I have no idea. How do I check?

[Bob Salomon]

Good question - I have no idea. How do I check?

Assuming that you have a Linhof gg and a Linhof Fresnel installed on your cameras then there should be no vignetting with the Linhof Reflex Monocular Viewer.

If there is I would suspect that the gg and/or the Fresnel need replacement.

[ghoonk]

I've just ordered 052522 fresnel for the Linhof and will update if this solves the problem

[VictoriaPerelet]

I always used Sinar system and Sinar bino viewer. I rarely use dark cloth. Few years ago, Sinar started to go unpredictable directions in thier budiness. I bought Technikardan and mono viewer. It was pretty much unusable (to my eyes) with 72mm and down lenses. With 210mm there was visible vingette. I bought few different fresnels and gg's - not so much help.

I gave up and switched back to Sinar. It can be something specific to personal vision or fact that Sinar is bino and has fine mirror adjustment knob.

Before trying Technikardan I never understood all heated up gg and fresnel discussions.

[Bob Salomon]

I always used Sinar system and Sinar bino viewer. I rarely use dark cloth. Few years ago, Sinar started to go unpredictable directions in thier budiness. I bought Technikardan and mono viewer. It was pretty much unusable (to my eyes) with 72mm and down lenses. With 210mm there was visible vingette. I bought few different fresnels and gg's - not so much help.

I gave up and switched back to Sinar. It can be something specific to personal vision or fact that Sinar is bino and has fine mirror adjustment knob.

Before trying Technikardan I never understood all heated up gg and fresnel discussions.

Your Sinar, depending on model, had either base tilts or asymmetric movements on the back. Since that meant that the image changed position on the gg the Sinar viewer required a moving mirror to recapture the image properly.
The TK has an optical axis movement on the rear standard so the image does not shift around like it does on the Sinar. So a moving mirror was not required.

With all those Fresnels and gg you bought did you try the Linhof ones? Also, were you using the correct center filters with those lenses to minimize the fall-off inherent in the wide angle lenses?

[Nathan Potter]

Bob Salomon, I would guess that you would recommend Linhof Fresnels and GG, and being a long time TK user with Linhof accessories I would do the same. But I have a question about the Linhof Fresnels with short focal length lenses for 4X5. Fresnels can be made in different focal lengths for different wide angle lenses and using a Fresnel that matches the focal length of the lens in use aids greatly in light uniformity across the field of view on the GG. It occurs to me that with very wide angle lenses, say 75 mm and shorter it would be nice to have a Fresnel which has a radially varying focal length such that the very obtuse angle ray bundles at the corner of the GG is directed orthogonal to the GG. - if you get my gist - yielding even GG illumination across the whole visual field. Of course as you point out a center filter would still be needed if one requires full even illumination across the screen.

But does Linhof employ such a radially varying focal length as I have described with any of their Fresnels? I've not used any Linhof Fresnels so have no experience with them. I do have a number of Linhof GG (maybe not manufactured by Linhof), especially the type with the clear stripes running from center to all four corners allowing a direct view of the aerial image for real critical focusing and these are a delight to use.

Nate Potter, Austin TX.

[Bob Salomon]

Nate,

Over the years Linhof has had many Fresnels. They keep updating them but they only sell one type for the 4x5 and larger cameras. And these are corrected for the commonly used range of optics used for that format. One way that you can tell is how well the image snaps in and out of focus. If the lens is too short for the Fresnel it just does not have that in focus snap while you are focusing. And if the Fresnel is not the proper one for the lens then the image will also tend to black out with small movements of the eye across the screen.

For the M679 and Techno cameras which are 6x9cm Linhof introduced at the last Photokina a new proprietary gg and Fresnel type system which is markedly brighter and more contrasty then any other system, including the old Acutte Matte screen which these replaced. But they would be prohibitively expensive for a 45 system and probably would not work well on larger formats due to the difference in focal legths used. These new screens are for 23 through 180mm lenses.

[ghoonk]

Turns out that i didn't have a fresnel. Bought three of eBay and the vignette by is significantly reduced. Thanks for the help, everyone!