Ebony wide angle fresnel?

[Paul Dunning]

Hi,

Appologies if this has already been covered somewhere.

I few weeks ago I got hold of the Ebony wide angle fresnel to use with my 45SU and 90mm lens and finding the correct way to fit it has been a challenge to say the least.

I finally got around to emailing Ebony for some guidance and they very promptly replied with...

"The wide-angle fresnel works well with the lenses wider than 150mm (in other words, it is hard with us to recommend using it with the lenses longer than 150mm). Could you please use the wide-angle fresnel putting it on the surface of the existing set-up (the standard fresnel and protective glass)?"

...So if I understand this correctly the current set-up (GG-fresnel-protective glass) stays exactly as it is and the wide angle fresnel goes on top of the protective glass, I assume rough side against the glass and smooth side facing me. I'm slightly worried about this as it mean it's likely to get scratched by the loupe so I was wandering if anybody could confirm that this is correct or comment on their experiences.

Thanks,
Paul.

[dave_whatever]

It should go between your existing screen (which in itself is a gg-fresnel combo) and the cover glass, with grooves faving towards the lens.

Cover glass definitely goes on last, otherwise yeah you will probably scratch the hell out of it with your loupe!

[Paul Dunning]

Thanks Dave,

So, just to clarify, the existing set-up is...

1 - GG (which has it's own fresnel etched into the same piece of material)

2 - Another fresnel, not sure what this one is but the camera came with it.

3 - Protective glass.

and what I should have is..

1 - GG (which has it's own fresnel etched into the same piece of material)

2 - Wide angle fresnel with grooves facing towards the lens.

3 - Protective glass.

Paul.

[dave_whatever]

Yep, as far as I'm aware thats correct.

[George Hart]

When I installed the Fresnel on my 45S some years ago the advice that I got from Ebony was that it should go on the lens side of the sandwich. This means that when you are putting the pieces in again, after removing the 2 clips from the camera back, the order is 1 Fresnel, 2 existing gg with graticule, 3 plain glass cover.

I queried these instructions at the time because the graticule gg is now a few mm posterior to where it was before. However, I am led to believe that the design of a Fresnel lens can affect the position of the virtual image. In use on my camera the appearance of the virtual image with wide-angle lenses, and the sharpness of the developed image on the film, are just fine.

Optical physics is very interesting but if my Fresnel makes it easier for me to take pictures with wide-angle lenses, and the end result is sharp, I'm happy to leave it there!

George

[Thingy]

Interesting. I understood that you simply mounted the fresnel with the protective glass on top, just like when using the Maxwell screen.

For clarification I suggest you PM either Baxter or Tim.

Baxter: memberlist.php?mode=viewprofile&u=162

Tim: memberlist.php?mode=viewprofile&u=209

[Paul Dunning]

Thanks everyone,

I fitted the wide angle fresnel in between the GG and protective glass (removing the fresnel that was already there) and it seems to work, focusing seems easy enough and the image seems reasonably bright but it's difficult to know if it's working as it should. I've PM'd Baxter. I think I'll also fire off another email to Ebony to see if they can elaborate on their previous (to me confusing) instructions.

Paul.