Which Heliopan CF for Grandagon 90/6.8

[carlos_co]

I tried taking a picture of a building using a substantial amount of front-rise and I got very serious light-fall off (not beyond the image circle because I can still see very dark features in the ground glass all the way to edge). Which Heliopan CF (3x or 8x) should I use with the Grandagon 90/6.8. I know Ellis uses and recommends a 3x for the 90/4.5 which if I recall correctly from I read in the Rodenstock brochure has some tricks in it to minimize light fall-off. By eye, the difference between the center and outer regions is definitely more than 1.5 stops at f6.8, but I'm worried that 3 stops from the 8x CF might be excessive. Does the light fall-off or difference between center and edges increase or decrease as the aperture is closed down to f22? Does anyone have experience on putting a Heliopan 8x CF on the Grandagon 90/6.8? I won't consider getting a "proper" 2x more expensive Rodenstock CF unless someone convinces me that both 3x and 8x Heliopan CF definitely won't work.

[ellis_vener_photography]

To clarify: I am using the Heliopan 3x on the 90mm f/4.5 Grandagon. One the reasons I have this larger lens is because of the much larger image circle which I need for my 6x17cm work. A side result is less falloff when shooting 4x5. Might this (image circle diameter) be a factor in your use of the f/6.8 version?

 

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The only "slow" 90mm I found in my research that produced a large image circle was the 90mm f/8 Nikkor SW: 235mm. Same as the Grandagon 90mm f/4.5 and the 90mm f/4.5 Nikkor. I haven't tested this lens however.

 

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Lightfall off improves as you stop down to f/22. Are you judging amount of fall off by what you see on film or on the groundglass?

 

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I think you should try the Heliopan 3x and judge for yourself. Spend the extra US$30+ and get the filter from a shop like Lens & Repro in New York or Photomark in Phoenix who will let you return it if it does not work for you, also ask for their advice.

[bob_salomon]

We stock some of the dneser Heliopan CF and have sold virtually none.

You would lose so much light (3 stops) + you must stop a lens down at

least 2 stops for the filter to work that the denser version is not

too useable for most people.

 

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Virtually every CF sold is either .40 (Rodenstock) or .45 (Heliopan

and others) so the more popular one should also work well for you.

 

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if you would like to receive a 2 page detailed explanation of center

filters and how and why they are used we can mail you the latest one

from Rodenstock.

 

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Of course we would need a mailing ad