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Trying to understand the optics on the Horseman VH. 90mm, super Topcore

Durio

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Hello everyone,
I got my hands on a Horseman VH.
However, something seems to be wrong.

1
The preview doesn't open completely. Only about 50 percent.
Is this normal for this lens?

2
When I use setting B with, for example, aperture 5.6, the preview iris opens completely. It is then slightly larger than the aperture iris.

3
Unfortunately, the image is only sharp in the center of the focusing screen. The sharpness decreases significantly towards the edges. There is also image distortion.

4
The high loss of sharpness towards the edges is obviously not dependent on the Fresnel lens. This effect can also be seen when only the focusing screen is used.

What is normal and what is not?
-Is the 50% aperture of the preview normal for this lens?
-Is the severe blurring at the edges (visible from 1/3 of the center to the edge) normal?
-Does this lens have to be used with high apertures?

Thank you very much for your help.
 
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Hi @Durio - welcome (back) to Photrio and to active posting on the forum!

The shutter doesn't look right the way it's shown here:

That's certainly not the way it's supposed to open on preview (or any other setting). This is a halfway-state between closed and open, so something is stuck in the shutter mechanism somewhere. Maybe it's something fairly simple like a bent preview lever. If the shutter works OK otherwise, you might work around the issue by using B mode combined with a locking cable release.

The distortion and loss of sharpness are a more serious issue. Is this lens complete; i.e. is the rear cell also present and correctly mounted inside the shutter? The severity of the problem goes far beyond a minor issue with shimming etc; it's almost as if an entire part of the lens is missing, or if the rear and front cells of two entirely different lenses are combined.
 
The shutter should be open or closed, not stuck half way. They get stuck half way when the lube gets thick, or contaminates the blades. The shutter needs a CLA. You can probably get it working temporarily by removing the lens cells, and flushing the shutter blades with solvent (lightly with isopropyl alcohol), but that would only make it work for a few months. A proper CLA is called for.

The lens is a 90mm, which covers 6x9. Is that the view of the ground glass, or is that the 4x5 adapter view? I don't have a Horsman so I can't tell. The lens is optimized for f/8. Sharpness only at the center is a sign of field curvature, or astigmatism and/or coma, which is a sign that the lens elements are not assembled correctly (spacing, or flipped element). Field curvature can be access by focusing new the corner.
 
1. That's not normal;
2. If I understand correctly, by "preview iris" you mean the shutter blades? At B the shutter should open completely as long as you're holding the release lever;
3-4. That's not normal. Coverage for the 90mm at f/5.6 is 130mm. I have this lens and use it on a 612 camera.

The shutter needs a service and I would think that the lens was assembled incorrectly. Maybe one of the elements is flipped or as @koraks suggested maybe the rear group is from a different lens. Here is the configuration:


You can also try to measure the lens board to film distance which is 92.6mm. The specs are found here: https://butkus.org/chinon/horseman/horseman_vh-r/horseman_vh-r.htm
 
I have a Super 90mm and yeah, it looks nothing like that, it (like all the 6x9 lenses from Horseman) is actually quite nice. If you post a clear photo of the rear of the lens I'll let you know if it looks like mine. Alternatively, search for "Horseman super 90mm" on ebay and you'll find some for sale in Japan and see if your rear group looks like the lenses on ebay. Unfortunately, unlike some manufacturers Horseman (Topcon) didn't seem to put serial numbers on both the front and rear groups. That would have made it easy to match.

I know a decade ago it was a thing to reverse elements intentionally to create swirly bokeh (or in really swirly distortion), but it doesn't seem like it would be very easy to do with this lens.
 
Hello,
I would like to repair this lens.

A
The iris appears to be defective. The preview does not open completely.
How do I access the iris blades?

B
A convex-concave lens has been installed upside down on the inside.
How do I open the mount?
 
Super Topcor
 

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I am sorry to say but servicing a shutter can't really be done remotely if you have no experience. For starters, removing the nameplate in this manner isn't necessary. To remove the front plate and the speed setting cam you need to unscrew the central notched retaining ring, which is locked by the small screw at 12 o'clock in your photo.

The preview lever uses a special screw: wide head and thin slot. You'll need a customized screwdriver to remove the lever properly and inspect its functionality. Servicing the iris blades (do you mean the shutter blades?) requires an almost complete disassembly of the shutter.

To open the lens you'll need rubber friction cups, lens spanners and a small flat blade screwdriver for set screws. But you didn't mention which lens group needs attention.
 
I have the same lens and would like to open it up to to clean and try to resolve the fact that the glass rattles.
I have no idea how to open it (maybe a rubber stopper like friction tool)
 
Durio said:
The iris appears to be defective.
Click to expand...

FYI: when we speak of the 'iris' of a lens, we generally mean the aperture. What you're referring to, is the shutter.

Going by the photo of the closed shutter, at least one shutter blade has become dislodged and may even be broken.

To disassemble the shutter, I think you start by screwing out the indented ring:

Then the faceplate underneath can likely be removed, providing access to the shutter mechanism. You will then have to proceed disassembly until you get to the shutter blade attachment.

Please keep in mind that trying to fix this is almost guaranteed to result in total failure if you don't know what you're doing. Leaf shutters like these are not self-explanatory, they are extremely sensitive fine mechanical devices and reliable guides to walk you through the process are very scarce and often refer to slightly (or entirely) different types of shutter from the one you actually have. Moreover, trying to re-fit the shutter blades is rather daunting as the blades are paper-thin metal and very easily bend or break; once that happens, they can generally not be repaired.

I would recommend finding another lens in a working shutter.
 
@koraks by dislodged shutter blade do yo mean the round piece at 4 o'clock? That's just a spacer above the blade. The blades look healthy to me.

OP, if you want to inspect just the preview mechanism, it is accessible after removing the name plate as explained above. You'll need to remove the speed cam and probably the cocking ring and spring. If I remember right there is a detent spring that indexes the open/close positions. Maybe it is misplaced.
 
Hello everyone,
I am delighted with your feedback so far. It's great to be in contact with this community.

The lens still had some defects. The Japanese shop had apparently dismantled the lens and not reassembled it correctly.

I unscrewed the inner part of the lens and took a look. A sketch from the manufacturer helped. It was not easy to see. With a little light from a flashlight, I was able to do it.
On the outside are achromatic lenses. On the inside is a convex-concave lens. It had been inserted upside down.

Since it was inserted correctly, the image is sharp again right up to the edge.

The preview is still defective. The repair seems very complex to me. I could use the optics in B mode for the settings. The aperture at 5.6 is sufficiently bright. The preview also opens completely in B mode.

What do you guys think?
 

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Chuck1 said:
I have the same lens and would like to open it up to to clean and try to resolve the fact that the glass rattles.
I have no idea how to open it (maybe a rubber stopper like friction tool)
Click to expand...
The inside of the inner part was slightly loose. The threaded ring could be turned with a screwdriver. The other sides can apparently only be loosened with special tools.
 
OAPOli said:
do yo mean the round piece at 4 o'clock?
Click to expand...
No, I'm referring to the arrangement of the blades, but on closer inspection it looks OK to me, too. Also since the shutter apparently works in other modes except T I presume here's nothing wrong with the blades and how they're mounted.
The malfunctioning T mode is probably a minor issue but I'd still be hesitant to try and fix it as it's all too easy to make matters much (much!) worse.

Durio said:
What do you guys think?
Click to expand...
Looking much better; in fact I see nothing wrong with the projected image!

I'd honestly just use the lens as-is and use B for preview and just enjoy the camera!
 
Here is what the shutter looks like sans front plate, speed cam and cocking lever. You can see the preview lever on the right.

 
OAPOIi, correct me if I’m wrong, but I recall the push-pull lever opens the shutter via a spring; thus the hold-up of the blades indicates the sector ring may be sticking.
 
@ic-racer the lever opens the blades by pulling on a little lug on the operating ring. The shutter needs to be cocked. I think the blades retract via the usual return spring on the operating ring. I don't think that a sticking ring would prevent the opening altogether since the shutter seems to operate normally otherwise. I suspect the problem is from a obstruction in the preview lever. Maybe the detent spring (3 o'clock under the retaining screw) is loose and jams under the lever.
 
Thank you for the clarification. I only have one push/pull Seiko. I repaired this same fault 25 years ago but have no notes. All my other Topcores are in Seikos with the lever.
 
OAPOli said:
Here is what the shutter looks like sans front plate, speed cam and cocking lever. You can see the preview lever on the right.

View attachment 414031
Click to expand...

Oh, that looks great. Almost like something from the steampunk scene.
Admittedly, the mechanics are very interesting. Presumably, everything has to be removed to get to the aperture blades or preview blades.
I'll leave it at that and use the B setting.
Unless someone has a technical drawing. .
 
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