Chamonix 45N1 and rodenstock 90mm 6.8

[sbaruche]

I am new to wide angle and large format
I just received my rodenstock 90mm 6,8
when I try to focus at infinity with below maximum compression front and back parallel I still have blurry image , I need to tilt the back and front to get a more compressed below and and then I can get a focus image on the gg
might be a dummy question
Do I miss anything ?
thanks

Sylvain

[Mark Woods]

Hello Sylvain,

On a "normal" design lens, the millimeter of the lens is based on infinity focus. So your 90mm lens is in focus at infinity when the center of the lens design (axially often near the center of the lens) is 90mm from the image plane. Your bellows may not allow the two standards to be that close. I use bag bellows with my 90mm lens on my Sinar 4x5 and it works great.

Hope this helps.

[sbaruche]

Thanks Mark
do you think a recessed board would help?
thanks
Sylvain

[Oren Grad]

Something doesn't sound right. Most compact 4x5 wood field cameras have no problem focusing a 90 to infinity. I just checked the Chamonix website, and the specification for the 45N1 indicates a minimum bellows draw of 45mm. Even if that's optimistic, it leaves plenty of room for the 94mm flange-to-film spec of the 90/6.8 Grandagon.

Are you able to post a snapshot of your camera set up with that lens?

[sbaruche]

THANKS
just found out I need to move the front backward and now if is OK , just found an image
you always learn by mistakes
thanks

[sbaruche]

http://www.largeformatphotography.info/forum/showthread.php?t=39735

[Lon Overacker]

Sylvain,

I am certain there are threads on this forum that address this issue. It is a known issue and actually adressed in the release of the 45n-2 Please see the website at:
http://www.chamonixviewcamera.com/45.html Check #7 in the updates: " 7) The Fresnel lens will be installed on top of ground glass to prevent
possible focus shift."

Personally, I have not experienced these focusing issues, but they have been widely discussed. I have used both a 90mm and 75mm on the 45n-1 without experiencing the issue, so I believe it's not across the board. But do a little search in this forum and I 'm sure you can find some lengthy discussions about this.

Lon

[GPS]

Lon, take to your senses. Sylvain's problem has nothing to do with the focus shift due to the position of the Fresnel lens in this camera.

[Lon Overacker]

You're right! I just read focus and wide angle and jumped to the wrong conclusion. Glad the OP figured it out anyway...

Lon

[Mark Woods]

According to members who have the 45 N1, the 90mm should work. They're nice cameras. I have the 11x14 and have used all sorts of lenses on it with no problem. It's a slightly different design, but still a really sweet camera.

[mortensen]

Sylvain,

Even better than setting the front standard backwards, put the back standard forward. Unlock the bottom screws of the back standard and move it forward. I use the second slot for my 90. This way you are perfectly sure not to see the bed of the camera when using full fall on the front with very short lenses. Another advantage of setting the back standard as much forward as possible is that you automatically align the back - instead of the rather unprecise 'eyesight' alignment.... it does take an extra 10sec to set up and take down, though... in my eyes well spent.

[JON BUTLER]

I can use a 47XL on 45-n1 & 2 with no problems at all but do use an Ebony screen plus a WA fresnel for 90mm and wider, much easer to view and focus.
JON.