Difference Between Arca-Swiss "N" & "Non-N" Type Cameras

[neil poulsen]

What's the difference between the Arca-Swiss "N" type and "Non-N" type cameras? Apparently the "Non-N" type cameras date before 2007.

I ask, because I noticed that they sell two different 6x9 roll-film backs (for Arca 6x9 cameras) for each of these two types of cameras. How are these roll-film backs different?

[foster_jb]

Hi Neil,

To keep it simple, if you have "N" type ground glass, then you want to use "N" type roll film holders. You cannot use "N" ground glass with "Non-N" roll film holders. If you did, your focus would be way off on your film.

The newer "N" version ground glass is about 3 mm less in depth than the older, "Non-N" ground glass. One of the reasons that Arca Swiss changed the depth in the newer ground glass was to be able to allow digital back users the ability to use really wide angle lenses (35mm) along with the Rotaslide sliding back on their Arca Swiss cameras. Without this newer type of ground glass, the rear flange on my 35mm lens hits inside of the standard when trying to use the Rotaslide; so it can't work properly.

Best,
Foster

[Rod Klukas]

What's the difference between the Arca-Swiss "N" type and "Non-N" type cameras? Apparently the "Non-N" type cameras date before 2007.

I ask, because I noticed that they sell two different 6x9 roll-film backs (for Arca 6x9 cameras) for each of these two types of cameras. How are these roll-film backs different?
To further clarify, the ground glass plate and the back adapter plate or roll back, must either both have an 'N' stamped on them or both must have no stamp.
That way the focus plane and the image plane will match.
Hope this helps.
Rod

[Emmanuel BIGLER]

And we could add that "N" or "non N" does not refer to the camera as a whole, but only to what is attached to the rear format frame of a 6x9 - 110 mm format frame or 141-to-110 format adaptor.
For example if you have a 141 mm format frame and the adaptor plate to 110, to this adaptor you can add either "N" or "non N" ground glasses or rollfilm holders.

[neil poulsen]

Thanks for the responses. I just purchased this recent Classic F, 6x9 equipment, so all of this is new to me.

It appears that I have all non-N backs. I checked my G.G., my roll-film holder with Arca Swiss 6x9 back attached, and my Polaroid back. The distance to the plane of focus is about 1mm longer for the two film holders, when compared to the G.G. There's no "N" on any of these accessories.

For the G.G., I'm measuring to the Fresnel lens, which I understand on Arca cameras should be between the G.G. and the lens. So, the difference of 1mm I suspect is because of this non-typical arrangement. (At least, I hope so.)

I think this might also explain why I need a recessed lensboard for my 47mm f5.6 S.A. Based on current specs, I didn't think that I would need a recessed lensboard. But I'm thinking that the current specs probably apply to the more recent N-type cameras.

QUESTION: Is this also true for the digital adapter backs, that there are two types? Or, were they all developed after the N-type change?

As I say, I appreciate the info. I'll be more alert to these subtleties as I find future accessories.

[foster_jb]

Hi Neil,

I can confirm that there are definitely two (actually, 3) versions for the digital back adapters; both an N and Non-N version exist. I have used both. When I went to the Rotaslide and wide lenses, it was necessary to change to the N versions of ground glass and adapter. Rod helped me with those purchases. He was very helpful and knowledgeable, and I can highly recommend him.

The "third" version of the digital back adapters are the cheap, chinese version you may have seen "on that auction site." I bought one to see what it was like, and found that it only fit on my old model B 2x3 Arca Swiss camera... It would not fit on my newer AS Monolith version, and I don't believe that it would work on your F-line. Beyond that, it isn't machined precisely, and the focus is slightly off, at least on mine. I wouldn't bother with these. Get a proper one if you are using a digital back.

Best,
Foster

[Emmanuel BIGLER]

For the G.G., I'm measuring to the Fresnel lens, which I understand on Arca cameras should be between the G.G. and the lens. So, the difference of 1mm I suspect is because of this non-typical arrangement. (At least, I hope so.)

Yes, Neil, definitely, do not worry.

Coming form the lens, you find, in his order
1/ the flat / glossy side of the Fresnel lens made of plastic
2/ the corrugated side of the Fresnel lens
3/ the frosted side of the ground glass made of ... glass; this is where you can see the image when focusing
4/ the glossy side of the ground glass.

Setting the Fresnel lens like A/S has several advantages. Once used to it, eventually you'll consider that all other combinations are not as good..

What you can touch at the back is glass; it can be cleaned easily without damage.
What you should not really touch but can actually be blown-off and carefully cleaned inside the camera is the flat / glossy side of the Fresnel lens.
Unless you disassemble the sandwich, you cannot have access to the corrugated side of the Fresnel lens and to the frosted side of the GG.
Both surfaces are fragile and act as excellent dust traps, but are not accessible to dust and stains in normal use.

The only drawback is that you do not have a "direct mechanical access" with a caliper or any purely mechanical measuring tool, to the proper registration distance between the image plane and the reference plane on the rear format frame.
In addition to some mechanical data that you can see and touch, you have to add some equivalent optical path inside the Fresnel lens which is fixed and does not change of course when focusing the camera.
In summary, as explained above, the only differences between N and non-N accessories is the distance between the image plane and and the mechanical reference plane where you attach the imaging or viewing accessories.

If we compare to another combination, for example adding a plastic Fresnel lens behind a classical GG, in terms of homogeneous light distribution, there is no difference with the A/S setting. But what you get at the back is one of the plastic sides of the Fresnel which are much more fragile than glass. Letting the corrugated side of the Fresnel accessible does not change much in terms of light distribution, but is not a good idea in terms of dust trap. In this case it is better to let the glossy side of the Fresnel lens accessible and put the corrugated side against the glossy side of the GG.
And the frosted side of the GG, in front of the sandwich, in this setting, is accessible to dust and stains. But you can directly read you registration distance with a caliper without any optical path, since the frosted side of the GG is the first surface hit by light after exiting the lens, like in any classical camera equipped with a plain ground glass without Fresnel lens.

[neil poulsen]

Hi Neil,
I can confirm that there are definitely two . . .




Yes, Neil, definitely, do not worry.


Thanks for the information . . .

I forwarded the information about the Chinese backs to the buyer who recently purchased my Arca B 6x9 outfit. With an adjustment for focus, he might be able to customize his camera for digital.

It's good to know the order of all the different parts from lens to eye. I verified this order on my camera to make sure it's correct.

I upgraded to the current Classic F as a step towards some day maybe getting a digital back. It's good to know these differences ahead of time.

Neil

[Phil Hudson]

Can anybody confirm the position and type of "N" marking I should be looking for on either adapter or screen? A photo would be really helpful for the archive!