Help: infinity focus with 9x12 Unknown beauty

[gimenosaiz]

Hello!

I received an unexpected gif last week :-) A beautifull unnamed 9x12 glass plate camera.
The only reference I can recognize are the manufacturers of the shutter: AGC; and the lens, a Scheneider Radionar 135/4.5 of 1928.
I'd like to use the focus scale as much as possible but I'm sure that it needs to be adjusted. I mean, it seems to have been unmounted and mounted again because the infinity doesn't aims at the camera. So I've tried to adjust it to mount it again correctly but there is something I'm not sure about. I'm trying to find focus using the ground glass that, by the way, it's not cristal clear at all!!!. The question is that I need to extend too much the bellows to find focus at infinity wich is something strange if I compare it with my Pacemaker and its Optar 135/27. And if I use that infinity focus point as a reference, if I try to focus an object at 1 meter the reference in the scale is completly wrong at that distance. The same for 2 meters ... So, the focus scale is not realiable at all.
What do you think?

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Thank you in advance !
Cheers
Antonio

[Pere Casals]

The question is that I need to extend too much the bellows to find focus at infinity wich is something strange if I compare it with my Pacemaker and its Optar 135/27.

Antonio,

A 135mm focal is a 135mm focal, so from lens rear nodal point to the image plane you have 135mm, (for distant subjects, of course). The single question is the flange to the rear nodal point distance, but it should not be far from diafragm plane...

I'd replace the GG by a clean one, you can get one for 4x5 (some 18€) at e*ay and make it cut.

Then I would place a measuring tape on the floor and I'd calibrate the focusing scale, using the loupe, I'd stick a label on it and I'd make the new markings.

Saludos,
Pere

[Len Middleton]

Hello!

I'd like to use the focus scale as much as possible but I'm sure that it needs to be adjusted. I mean, it seems to have been unmounted and mounted again because the infinity doesn't aims at the camera. So I've tried to adjust it to mount it again correctly but there is something I'm not sure about. I'm trying to find focus using the ground glass that, by the way, it's not cristal clear at all!!!.
Cheers
Antonio

Antonio,

If the distance from the focal plate (ground glass) to the lens for the two 135mm lenses is close, then maybe the bed scale is not the right one for the lens.

If the lens and bed scale both original to the camera then likely would not be a problem, however if one of them been changed...

Have a look and let us know.

Enjoy,

Len

[Bob Salomon]

Antonio,

A 135mm focal is a 135mm focal, so from lens rear nodal point to the image plane you have 135mm, (for distant subjects, of course). The single question is the flange to the rear nodal point distance, but it should not be far from diafragm plane...

I'd replace the GG by a clean one, you can get one for 4x5 (some 18€) at e*ay and make it cut.

Then I would place a measuring tape on the floor and I'd calibrate the focusing scale, using the loupe, I'd stick a label on it and I'd make the new markings.

Saludos,
Pere

Pere, 135mm is the nominal focal length, not the actual focal length. Any two 135mm lenses, from the same or different manufacturers, will vary +- from that nominal focal length.

[Pere Casals]

Pere, 135mm is the nominal focal length, not the actual focal length. Any two 135mm lenses, from the same or different manufacturers, will vary +- from that nominal focal length.

Thanks for pointing it. Single Radionar in the schneider vintage lens data looks it is the 40mm, it says an effective F of 41mm.

https://www.schneideroptics.com/info.../2,8-40mm.html

[Steven Tribe]

There is no garantee that 135mm lens is the one that was originally mounted on the camera from new! The early 9x12 folders most often had a F6.8 DAGOR or a copy mounted. As these cameras were used for at least 10 years by the owners, it may have been replaced by an F4.5 lens which came to dominate the market (Like the one mounted on yours!). Typical focal lengths used by DAGORS on 9x12cm were 120 or 125mm, whilst the F4.5 are mostly longer - again like yours.

[Jac@stafford.net]

Antonio,

A 135mm focal is a 135mm focal, so from lens rear nodal point to the image plane you have 135mm, (for distant subjects, of course).

Oh, should our universe be so accurate. Do not mistake nodal point with flange focal distance. For most of our LF cases, focal flange distance is our reference point because it is simple to measure.

[Nodda Duma]

Oh, should our universe be so accurate. Do not mistake nodal point with flange focal distance. For most of our LF cases, focal flange distance is our reference point because it is simple to measure.

Pere is correct, actually. The flange focus distance isn’t the number stamped on the lens.

[Pere Casals]

Oh, should our universe be so accurate. Do not mistake nodal point with flange focal distance. For most of our LF cases, focal flange distance is our reference point because it is simple to measure.

Jac, OP finds the bellows extension abnormal, I was only pointing (post #2) that the bellows draw has to around the (effective) focal, so around 135mm, as this is not a tele or retrofocus design.

[gimenosaiz]

Hello!!

Woow, thank you very much everybody.

My first choice was to extend the bellows 135mm ... +- But, no focus at infinity.
The focal scale was wrongly mounted as I've said.

Although the image in the GG is not very clear because the crystal is quite dim, I think that I get focus at infinity at around 16 cm!!!! (from the rear of the lens to the film plane).
By the way, the GG has the rough surface inside the camera. I think this is correct.

Thank you!
Cheers
Antonio