lefthand side of image unfocused/lense problem?

[K. Mayer]

I have been using this site as a valuable source of information for a long time. Now I finally have a reason to register: The following problem has been troubling me for a while and I hope someone can help me:

Last month I exchanged my Sinar to a Linhof Thechnikardan and had to get my Rodenstock Grandagon-N 75/4.5 changed from a Sinar to a Linhof lenseboard. The guy in the shop mounted it to a Toyo-View lenseboard instead, claiming that it should still work. It sits quite loosly in the camera, but I thought I will give it a try.

Last week I used the camera with this lense for the first time and I have noticed that the lefthand side of the image is somewhat unfocused.
Since then I have been doing numerous testshots (of a carpet hanging flat on a wall)
- with 10mm shift to the left
- with 0mm shift
- with 10mm shift to the right

The lefthand side of the image is always blurry (a strip of about 2cms) !

The guy in the shop claims I am too close to the edge of the image circle. But I doubt that! I have been doing some wild shifting with that lense when I still used the Sinar, It gave me black corners every now and then but never any blurriness!

Do I have a
camera problem
a problem with the lenseboard
or a problem with depth of field (aperture 22.5 for a flat, perpendicular object)????

Please help, any comment much appreciated.

Thanks,

K. Mayer

[Walter Calahan]

Sounds like an alignment issue, but without being able to see the camera, my thought is a shot in the dark.

[Gem Singer]

Did he remove the little indexing pin on the back if the shutter before mounting it on the lens board?

If not, the lens might be mounted with a slight tilt.

Some lens boards have a recessed area where that pin fits. The new lens board might not have one. Removing the pin will solve the problem.

[eric black]

my guess is that the ground glass might not be shimmed correctly or is somehow out of alignment. If the image is in focus at all points on the ground glass and then it doesnt translate to the final image on film- then the positioning of the film holder would appear to be different from the focussed image on the glass. I would look into that first with a reputable repair facility. the second thing I would look at is the loosely mounted lens- that's not a good thing either.

[willwilson]

I use this lens all the time. It is very sharp and has decent coverage for a 75mm, plenty for 10mm of shift/rise. A small amount of swing or tilt induced by miss mounting or the lens board not sitting snugly would not produce blur at f22.5, in this type of test. Are we talking about blur or slight soft focus?

Does the same side blur/soft focus when you apply tilt/swing that would normally bring that area into sharper focus? If it remains blurred you might have some type of internal problem.

If it's not the pin issue Gem mentioned, perhaps one of the lens elements is cross threaded, most likely the rear element as you do not remove the front element to change a lens board. You can test this very easily, just unscrew the rear element slightly and see if it turns smoothly. It should be tight at first and then turn very easily and smoothly (righty tighty - lefty loosey). If its not cross threaded then you need to do further testing or send it to SK Grimes.

[David A. Goldfarb]

Alignment is more critical with wide lenses. Do you have other lenses you can test on this camera? Have you checked the alignment of the camera? If it's a Technika-style Toyo lensboard, it shouldn't be so far out of alignment as to cause this sort of problem and shouldn't fit loosely, though it might not be quite as tight a fit as a Linhof board.

The 75/4.5 Grandagon-N has plenty of coverage for 4x5". I use it on 6x17cm.

Another possibility--are your filmholders seated properly in the back? If not, that would cause the problem you are describing, and it would be very obvious with any lens.

[Dave Moeller]

The first question that comes to my mind: Is the image sharp when you view it on the ground glass with a loupe? If it's sharp on the ground glass but fuzzy on the film, you've got a misalignment between the ground glass and the film. Your ground glass may be in the wrong place (shimmed improperly, for example), or your film holder(s) may not be seating properly in the camera back.

One other possibility: Are you sure that the problem is that the edge is fuzzy, and not that it's exposed differently than the rest of the sheet? I ask this only because I thought I had an edge that was fuzzy on a negative once when I first glanced at it, but when I actually stopped and looked at it I realized that the edge was slightly underexposed. It's a long shot, but worth checking if nothing else is working out.

Best of luck.

[K. Mayer]

thanks for the answers, it gives me some things to try out.
I did also suspect that it much be some kind of alignment problem.

To answer some of the questions:
it is in fact more of a soft focus rather than a blur
I have tried with other lenses (115, 250) and don't have the same problem
the lensboard can be moved a 1,2 millimeters each way in line with the camera
the image is also out of focus on the ground glass

Could I have an alignment problem that is always there but only shows when I use the wideangle but not with the other lenses?

[Gem Singer]

It's sounding more and more like the lens was mounted without removing the tiny index pin that screws into the back of the shutter. I have a few Sinar boards that have a recess for the pin. I have also used Toyo boards in the past that did not have a recess.

You stated that the lens worked fine when it was mounted on your former Sinar Lens board.

If a shutter is mounted with no recess for the pin, it will tighten down on the lensboard but the shutter will be slightly tilted. The problem will show up as you have described- a mis-alignment on the GG- unable to focus the entire image sharply.

Have the tech un-mount the shutter and check to see if the index pin is still there.

[Peter K]

As David mentioned before alignment is more critical with wide lenses. So you can swing the back and look if the blur vanishes. If so back and front standard are not parallel in the zero position and the camera has to be aligned in the factory.

[Dave Moeller]

A couple of questions that might help diagnose what's going on: Does the image get unsharp abruptly, or does it "fade" from sharp to fuzzy. Is the edge of the fuzzy area parallel with the edge of the film, or does it curve?

You definitely can have a problem that's related to only one lens, though I'm having a hard time visualizing what sort of problem would lead to the effect that you're seeing. If the rear element of the lens doesn't protrude past the rear barrel, set the lens down on a table and check to make sure that everything that should be parallel with the table is parallel. This would include the lens board, the back and front of the shutter, and the top of the front lens barrel. If you're comfortable doing so, you might want to check the lens cells to make sure they're not cross-threaded in the shutter and that they're screwed all of the way in. (Just hand tight...they don't need to be screwed down hard.) Don't do any of this if you're not comfortable handling your lens these ways.

You mentioned in your original post that the lens board can be moved "in line with the camera". By this, do you mean that you can move it in the same direction that the bellows fold up? If so, you might try folding up a bit of paper and sticking it in between whatever locking mechanism your camera uses for lens boards and the board itself. That should hold the lens board tight so that you can see if that's the problem.

This is a stumper. I hope you figure it out soon...I'm sure it's frustrating.

[K. Mayer]

The edge of the soft focus area is parallel to the edge of the film and it starts quite abruptly.
The lensboard moves up and down and left and right but can't be tilted. At one point I thought I might be moving the lensboard when using the cable release - but I guess that would blur the entire image, not just one part of it.

I will go back to the repair shop tomorrow. I am happy that I am somewhat prepared now, as I thought it was a bit unconvincing to blame the problem on the image circle.

[SAShruby]

Maybe lens fell during mounting on the ground and on of the glass elements chiped and created a blur on one side.

[Bob Salomon]

You can easily tell if there is a problem with the lens by rotating it on the board and shooting a test shot. If the soft area moves then there is a problem with the lens. If it stays in the same place then it is a problem with the board or the camera.

[john borrelli]

A lot of good things to look at have been mentioned.

I would check the lens retaining ring along with the pin (which looks like a tiny screw). I once screwed my lens retaining ring in backwards. Because of this, the ring did not extend through the hole in the lens board, the result was that that the lens was a little loose on the lensboard and the lens was at a slight off angle to the lensboard.

[Leonard Evens]

When I got my f/4.5 75 mm Rodenstock, I noticed something similar, which I had not seen before, even with my f/6.8 90 mm lens. It turned out to be due to poor alignment of the standards. As others have mentioned, alignment may be more crucial for wide angle lenses, particularly if you focus at roughly the same subject distance. For example, for the same inadvertent tilt, at the same subject distance, the angle the exact subject plane makes with the vertical is twice as great with a 75 mm lens as it would be with a 150 mm lens.

Alignment problems could arise either because the lens is mounted with a slight tilt or swing, most likely because of the pin, or because the standards are out of alignment.

Here is one way to test the alignment of the standards. Point the camera down so it is plumb and one of the standards is level in all directions. For example, you can use a small level on the ground glass. Then test to see if the other standard is also level. If the geometry of your camera allows it, you may also use a dial caliper to measure the distances between the standards at the four corners to see if they differ. Neither of these methods will guarantee exact alignment, but you should be able to reduce the angle between the standards to less than a quarter of a degree.

The f/4.5 75 mm Grandagon has an image circle (when focused at infinity) of 195 mm, and it would be larger for close subjects. That should allow shifts/rise/fall of 24 - 28 mm, depending on the orientation of the frame. I use mine regularly with such shifts. Of course, there is reduction in intensity, and sometimes it is hard to distinguish that from loss of sharpness. But when used with a center filter, I don't see any obvious loss in sharpness at the corners.