Linhof Technika gg zeroing

[MagasAtis]

Hello all,

I have read through a lot of threads about this topic, but I think I do not understand something...

As I understood:
In case of Tech IV, the ground glass is not zeroed, therefore it needs cams matched for the particular camera. In case of Tech V or later, the gg is zeroed for interchangebility of cams and lens. This zeroing can be done with proper shims below the ground glass.

So my question: if the ground glass is zeroed with the camera body, how can the gg be in the same position as the film?

Cheers,

Attila

[Bob Salomon]

The gg is zeroed to the position the film emulsion will be in. That is done to the basck, not the body.

[Tony Lakin]

Whilst we are on the subject, I have checked to see if the ground glass is in the same plane as the film in quite a few large format cameras using a digital depth gauge, the only camera that I have tested which is spot on is my 55 year old Linhof Tech III mark 5

[Bob Salomon]

Whilst we are on the subject, I have checked to see if the ground glass is in the same plane as the film in quite a few large format cameras using a digital depth gauge, the only camera that I have tested which is spot on is my 55 year old Linhof Tech III mark 5

Spot on to what? Film sags it is not flat in your holders.

[Tony Lakin]

OK
The measurements were taken with the revolving back removed and laid flat on a bench so may not have been 100% accurate, does Linhof or any other LF camera manufacturer allow for film bulge when setting the ground glass position in relation to the film plane? and if they do what if the end user uses a vacuum film back would they have a problem?

[MagasAtis]

The gg is zeroed to the position the film emulsion will be in. That is done to the basck, not the body.

Thanks Bob! Just as I thought...

Now the only thing I do not know, is what is adjusted in the rangefinder system (in case of Tech V or later models), to make the camera capable to use cams, which are not grinded to that particular camera (only for the lens).
So what is the difference between Tech IV and Tech V rangefinder system? I know that Tech IV must have a cam grinded to the particular camera and lens, and V must have a cam only for the lens, but why?

[Bob Salomon]

Thanks Bob! Just as I thought...

Now the only thing I do not know, is what is adjusted in the rangefinder system (in case of Tech V or later models), to make the camera capable to use cams, which are not grinded to that particular camera (only for the lens).
So what is the difference between Tech IV and Tech V rangefinder system? I know that Tech IV must have a cam grinded to the particular camera and lens, and V must have a cam only for the lens, but why?

Nothing is adjusted on the rangefinder. The cams must be cut to the lenses. If you want the IV to have a 0 back then the service center adjusts the back. But no amount of playing will make a cam cut for one lens work over the entire focusing range with a different lens of the same marked focal length.

On a Master Technika and a V the backs are zeroed. On a III and IV the backs were not zeroed at the factory. But the service center can zero multiple IV cameras so they can accurately share a cam.

[Bob Salomon]

OK
The measurements were taken with the revolving back removed and laid flat on a bench so may not have been 100% accurate, does Linhof or any other LF camera manufacturer allow for film bulge when setting the ground glass position in relation to the film plane? and if they do what if the end user uses a vacuum film back would they have a problem?

What vacuum back? Linhof experimented with vacuum sheet film holders and gave them up because they could not hold pressure properly. Hoffman made some that worked better but the gg might require adjustment. Linhof Aerial Vacuum roll backs for 5" film were adjusted for the film position and worked just fine on Technika cameras.

[MagasAtis]

Nothing is adjusted on the rangefinder. The cams must be cut to the lenses. If you want the IV to have a 0 back then the service center adjusts the back. But no amount of playing will make a cam cut for one lens work over the entire focusing range with a different lens of the same marked focal length.

On a Master Technika and a V the backs are zeroed. On a III and IV the backs were not zeroed at the factory. But the service center can zero multiple IV cameras so they can accurately share a cam.

It is clearly understandable that the cam must be grinded to its own lens.
It seems that I was confused about the gg and the back... so the back is zeroed not the gg to ensure the interchangebility of cams between cameras.
Is there anything that can be adjusted in the back? (sorry if I am too curious...)

[Bob Salomon]

It is clearly understandable that the cam must be grinded to its own lens.
It seems that I was confused about the gg and the back... so the back is zeroed not the gg to ensure the interchangebility of cams between cameras.
Is there anything that can be adjusted in the back? (sorry if I am too curious...)

The gg is shimmed in the back. The shims are adjustable.