How do you center the optical axis in Linhof Technika?

[wieslaw1]

Occasionally, with wide angle lenses (65mm, 120mm) I observe

vignetting on my negatives. Usually, the resulting dark corners are not

symmetrical on the negative, and often vignetting is partial, i.e. only one or

two corners are dark. This effect is more pronounced with even shorter

lenses, like 58mm.

 

The lens holders in LF are such that the center of the lens opening is

shifted towards the bottom by few mm, (Wista holders which can be used

on LF are symmetrical), however, the eccentric lens position cannot be

the issue here, because the Linhof designers obviously knew what they

were doing.

 

I believe the vignetting might be due to the relative position of the lens in

its wide angle lens holder (which allows about 1 cm movement for the

focusing purpose) and the distance the entire assembly (lens + the

holder) is placed inside the camera housing, relative to the ground glass.

Even so, the vignetting should be symmetrically distributed on all 4

corners. As shown here this is not so. Besides I cannot see the

vignetting on the ground glass while taking pictures.

 

Any suggestions here?<div></div>

[wieslaw1]

I should add that the lower parts of both negatives are clear, no

vignetting.

[leonard_evens]

Perhaps I don't understand your question, but I thought the Technika had enough movements so that you could correct andy lack of centering. You say you can't see the vignetting on the gg. Usually, there are cutouts at the corners of the gg, and supposedly if you look through them at the appropriate angles, you should be able to see vignetting. Of course, if it is lack of coverage for the lens and the 'vignetting' is not true vignetting but drop off in intesnity because you are outside the circle of illumination, that wouldn't show up that way.

 

Sorry if this is off topic and not too useful.

[bob_salomon]

What lensboard is the lens mounted on? For the Wide Angle Focusing Device Linhof made a

special lensboard the 001005. That is the only lensboard recommended by Linhof for use

with the Wide Angle Focuing Device. Unfortunately both the lens board and the Wide Angle

Focusing Device are no longer made.

 

Many people just mounted their lenses on any flat Technika 23 board for use with the

Wide Angle Focusing Device rather then on the one made for it. It sounds like that is part,

if not all, of your problem.

 

Also is the fall off in useable, printable parts of the negative or is most of it occuring

outside the normally useable parts of the negative?

[brian_ellis19]

Vignetting often isn't easy to see on the ground glass, it's much more obvious on the negative than it is on the ground glass so you often have to look very carefully to see it and when you do it usually won't be nearly as pronounced as it appears on the negative.

 

Are you using any movements? And are you checking for vignetting by looking through the cut-out corners of the ground glass after applying the movements? If you do that and the aperture opening is shaped like a football (American football that is) you need to stop down until the shape is circular or octagonal(?).

 

I assume you're not using the wide angle focusing device with your 120mm lens, you certainly don't need it with that lens. And if you're getting the vignetting with that lens as you say you are then the problem isn't with the wide angle focusing device and lens board.

 

As you surmised, the Linhof off-center cut-out hole in the lens board isn't causing the problem. The hole is cut that way just to ensure that the hole is centered on the film given the design of the front standard, which would cause the hole to be slightly off-center on the film if it was centered on the lens board.

[frank]

One more question to Bob:

Is it possible to combine a Nikkor SW 65/4 mm with Linhof's special lensboards with helical mounts? I think this might be more comfortable instead of using the old fashioned focussing device for the Technika.

 

Thanks

 

Frank

[bob_salomon]

Frank,

 

Linhof now makes a special set of lensboards with helicals. They are available for 47, 58

and 65mm Schneider lenses. They would not work correctly with other manufacturers

lenses.

 

Both Rodenstock and Schneider make helicals for 65mm lenses that work properly with

their lenses. If the Nikon lens has the same effective focal length and flange focal length as

either of these then one of these may work. Both mount to a flat board with a 3 hole. How

well they would work on a Technika inside the body would be open to question. We have

no reports of anyone having done it.

[frank]

Bob,

 

Wow, that was a quick answer! Thanks a lot.

I think about using my 65 mm SW-Nikkor that I have left from my Technikardan 6x9 with a Rollex 6x12 on a Super Technika V. So a helical seems to be a fine choice...

[Troll]

Center the optical axis by sliding the lens standard all the way into the camera body, and centering the lens with the "X" at the center of the ground glass.

[wieslaw1]

I am using original Linhof board, 74 x 81mm with T E C H N I K A

letters protruding at the top, which is mounted sidewase in the

wide angle focusing device. All of this sits in the camera

housing and practically, there are no options for movements.

The lens is Super Angulon 65/5.6.

 

Forget abot the 120mm lens. This lens sometimes vignettes

because of a small circle of coverage, and with filters on, I know

that, but again the dark corners are not symmetrical.

 

With S. Angulon all vignetting is on the useful part of negative,

like the example above. But it is not always observed.

Sometimes is there, some other days in the field it disappears,

and the negatives are uniformly exposed from corner to corner. I

never shoot with a larger aperture than f/22.

[bob_salomon]

"Linhof board, 74 x 81mm with T E C H N I K A letters protruding at the top"

 

This describes almost all Linhof boards but does not indicate if you are using the correct

Linhof board.

 

As you have seen Linhof does not stamp the model # of the board on the board. Only on

the bag the board arrives in. So we still don't know if you have the correct board. And,

since the board is no longer available new, we have no way of measuring where the whole

is in relation to other Linhof 23 boards.

 

Marflex may have a reference that could tell which board you actually have. They are at

marflex@aol.com

[wieslaw1]

I bought the board second-hand, so there is no reference. But

how a wrong board can be attached to the original wide angle

focusing adapter? The dimensions are very tight. I'll try to post a

picture of the board here later to-day.

 

Thanks,

[bob_salomon]

The Wide Angle Focusing Device accepts all Technika 23 lens boards. They are all the same

size. The hole in the boards differ. That is why you had no problem mounting the board.

[wieslaw1]

Here it is scanned image:

 

Bob - could you explain what is the reason the holes differ, only

in sizes for different lenses?, or are they also shifted from the

center of symmetry. - Thanks.

[bob_salomon]

One board was made with the hole positioned properly for the Wiode Angle Focus Device.

The other was not.

[wieslaw1]

Ok, so what is the situation with the board shown? Is it correct or

not

[bob_salomon]

Have no idea as we have nothing to compare it to. The boards in question are discontinued

items and we have no stock. Marflex may have specifications as may Linhof service centers in

other countries. They are who this question should be directed to.

[wilbur_wong]

The hole for the Technika should be lower than centered to be centered on the ground glass. If you look at the bellows from the side, you will see that the part close to the focusing bed is more tapered than the top part of the bellows.

 

Or conversely, take off the film back of the camera and look at the bellows while the bellows is closed and a lensboard installed. If the hole is in the right position. The lens will be centered within the film area.

[wilbur_wong]

BTW what aperture are you shooting at, most lenses don't reach full coverage at less than f:11 or so.