LINHOF TECH III CAM QUESTION

[bicycletricycle]

I JUST GOT A LINHOF TECH III 6X9 AND IT IS REALLY A WELL THOUGHT OUT GOOD FEELING CAMERA. HAVE A QUESTION ABOUT CAMS. I KNOW THAT THEY ARE MATCHED TO THE CAMERA BODY AND LENS BUT I WAS WONDERING HOW A LENS OF THE SAME FOCAL LENGTH COULD POSSIBLY WORK DIFFERENTLY. MAYBE ALL 100MM LENSES ARE NOT REALLY EXACTLY 100MMS. ANYBODY TRIED TO USE A DIFFERENT LENS SAME FOCAL LENGTH COMBO TO SEE HOW IT WORKS? ALSO I CAME WITH A 105MM F3.5 XENAR. ANYONE KNOW THE IMAGE CIRCLE OF THIS LENS OR KNOW HOW SHARP IT IS? I GUESS THAT IS A HARD QUESTION TO ANSWER, MAYBE COMPARED TO MY HASSY 80MM PLANAR T*.

 

[David A. Goldfarb]

The nominal focal length is usually slightly different from the actual focal length, mainly due to variations in the refractive index of the glass. Another cam might come close, but it won't be as precise as a cam ground for the particular lens, which is an issue if you want to shoot wide open.

 

[Dave Parker]

I know your excited, but you need to turn your caps lock key off, it looks like your yelling.



R.

 

[bicycletricycle]

its strange isnt it?

WHY DOES IT LOOK LIKE SOMEONE IS YELLING WHEN THEY HAVE THE CAPS ON? never understood that. Also if the nature of the problem is that they are slightly different focal legth than should the rangefinder be off the same amount all the time. So you could always focus a little short and it would be fine? Any one had a new cam machined lately? how much did it cost and who did you go through?

 

[Dave Parker]

WHY DOES IT LOOK LIKE SOMEONE IS YELLING WHEN THEY HAVE THE CAPS ON? never understood that.

Just one of those things that have been around since the dawn of online chats many moons ago, when we did not have any type of graphical interface and the only way you could show emphisis was to turn your caps lock on...been considered bad manners every since.

R.

 

[bicycletricycle]

ALL RIGHT, IM SORRY!

Just kidding.

 

[df cardwell]

On the III bodies, the relative placement of the film plane is variable. SO, a given cam is based upon the specific lens on a specific body. You MIGHT get close, but you'll have to move the groundglass to agree with the cam ( and adjust the infinity stop, which - I think - is a simple notch on the rail.

And THAT will undo the accuracy of the existing cam and lens you have.

A wide angle lens will be less of a problem; you can fine tune the lens on the board by shimming it.

Linhof changed this system in the IV.

As for the 100 Xenar vs 80 Planar ? The Planar will be nominally better wide open, and is a newer lens. The Xenar, however,is superb.

have fun

 

[bicycletricycle]

ground glass placement variations due to variable maufacturing tolerances?

that is strange, everything else seems so well fitted, I cant imagine each camera would have a different GG placement but that would explain it. i guess in that way it is kind of like the original pre "C" leicas, in that they also varied in lens to film registration from camera to camera. Thaks for the info about the lens.

 

[David A. Goldfarb]

Linhof changed this system in the IV.

Actually the Tech V was the first to have a "zeroed" groundglass. The 4x5" IV, V, and Master Tech have mechanically interchangeable cams, but Tech IV cams are matched to the body, and V and MT cams don't have to be. The groundglass rests on adjustible shims that are calibrated at the factory, and if you have new lenses cammed, you can have Linhof service check the groundglass calibration.

Leica rangefinder lenses are also individually machined to account for variations in focal length among lenses of the same design.

 

[df cardwell]

Right, David. How can you remember that stuff this late at night ?

don

 

[bicycletricycle]

are the 6x9 and 4x5 cams interchangeable?

are the 6x9 and 4x5 cams interchangeable?

 

[David A. Goldfarb]

are the 6x9 and 4x5 cams interchangeable?

No. The Linhof 6x9 cameras use three-lobed cams for three different lenses. You can rotate the cam to the lens you're using. On the Linhof 4x5" cameras there is one cam per lens, so you have to switch cams when you switch lenses, if you want to use the rangefinder.

 

[bicycletricycle]

6x9 cams

does anybody still make these cams for newer lenses?

 

[David A. Goldfarb]

It depends. If you have a Tech IV 4x5 or Tech V 6x9 or 4x5 or Master Tech 4x5, then Marflex or any other Linhof service (depending on what country you're in) can make cams for many modern lenses.

Richard Ritter makes cams for the 4x5" Tech III. I asked him once if he made them for the 6x9 Tech III or IV, and he recommended just looking for one with a set of three cammed lenses, implying that it was not economical for him to make cams for the 6x9 cameras.

 

[Oren Grad]

Also if the nature of the problem is that they are slightly different focal legth than should the rangefinder be off the same amount all the time. So you could always focus a little short and it would be fine?

No. There are two key parameters involved in setting up the rangefinder system, infinity stop position and cam slope. Incorrect register of the ground glass results in a constant error that can be compensated by resetting the infinity stops for the lens. But change in focal length requires a different cam slope - that is, the error will be proportional to focus travel rather than constant.

Actually, that raises a different question for you Technika III mavens: just how variable was the ground glass register? Enough to cause a problem with film plane register when swapping Rollex backs?

 

[Curt]

The cam on my 2x3 Busch is straight with no lobes, wouldn't you think that it would be linear? It has the original 101mm lens and a Kalart so it's original equipment. I was thinking about putting another lens on it but I had such fun with the tuneup adjustment of the existing lens I just put it aside. Besides the lensboard has four screws that are specific to the camera and I haven't got the time to find new ones. I was thinking about replacing them with four that would have knurled heads to make field changing easier. I too am not sure about other cams for other lenses. Given enough time and experimentation I could figure it out.

 

[df cardwell]

CURT: I don't know if I understand you.

A Busch cam, or Graflex, is linear. A Linhof is NOT. The Linhof system is also more accurate.

OREN: I don't have one to check, but if reason (and memory) serve, the groundglass register = film plane.

 

[bicycletricycle]

i think that i may try to make my oen, cant be to hard, can it?

anybody tried making one? anybody know how they are made?

 

[David A. Goldfarb]

I think there are instructions somewhere on the net for making MPP and Super Graphic cams.

If the point of having a Linhof with cammed lenses is to have a really accurate rangefinder, though, it's probably best to leave it up to a shop that can do it precisely and accurately with factory equipment.

 

[Oren Grad]

OREN: I don't have one to check, but if reason (and memory) serve, the groundglass register = film plane.

I understand, that's the way it's supposed to be. What got me wondering, though, is that if the ground glass register on a III varies enough from one body to another to require body-specific cams for the lenses, why isn't there a problem with interchanging sheet film or roll film holders as well?

 

[David A. Goldfarb]

I understand, that's the way it's supposed to be. What got me wondering, though, is that if the ground glass register on a III varies enough from one body to another to require body-specific cams for the lenses, why isn't there a problem with interchanging sheet film or roll film holders as well?

I think the groundglass can be accurate with respect to the film plane without necessarily being uniform from one body to the next with respect to the rangefinder cam and the cam with respect to the follower on the focusing track.

 

[Oren Grad]

I think the groundglass can be accurate with respect to the film plane without necessarily being uniform from one body to the next with respect to the rangefinder cam and the cam with respect to the follower on the focusing track.

OK, that certainly makes sense as a logical possibility - if GG and film are consistent relative to each other, but the bearing surface against which they're both seated varies with respect to the RF mechanism.

 

[df cardwell]

Like Historical Literature, it's always helpful to put yourself into the spirit - and technology - of the times when we're figuring out vintage cameras.

And that's half the fun.

d

 

[Curt]

Sorry to butt in on the Linhof forum here I don't have one but I was interested in the the technical design of focus cams.

 

[df cardwell]

It IS interesting.