a fake Topcor 90mm f5.6 (Horseman)?

[landstrykere]

so I got this Horseman 985 last week. Took a 6x9 test roll but only now does it hit me that it is seriously wrong. See, it's a f3,5-f32:



the manual says the 90mm which comes only in "Super" (ie. wide image circle suitable for 4x5) is f5,6-f45:
https://www.cameramanuals.org/prof_pdf/horseman_985.pdf (page 10, printed 7)

I should have jumped when I opened the box and inspected the camera and even more when I tested it with a first roll and was setting the lens at f3.5 and f4 ...but well I guess I was too much distracted by other things since this is my first "technical" camera.
On the resulting images of the first roll I didn't notice differences at f3,5 f4 f5,6 and indeed the iris closes only from f8, there's a bit of a blade visible by the edge at f5.6 but could be just tolerance related to the design being 5 blades:



I was thinking two possibilities:

• may be a repaired lens, shutter was replaced but with the one of a Pro 105mm
• it˝s a fake: a Pro 105mm f3.5-f22, with the front of a Super 90mm.

In order to see if the diameter of the front element is bigger than the hole of the front, I should unscrew the front but I see no notches for a spanner, so I guess it would require more disassembly manipulation than I want to do now.

I measured the length with a caliper and weighted the lens, it is closer to the figures of the Super 90mm, for sure the weight, clearly ~220g like for a Super 90, instead of ~240g for the Pro 105mm (this all in the manual). But...

Since the circle is stated to be 150mm at f22, but the Pro 105mm is 120mm (at f22), I took the 4x5 enlarging back that came with the camera, loaded two sheets of Retropan-320, the only 4x5 film I bought in order to try my hands at 4x5. Indoors, lens set at f8, focusing with a 5x loupe (my Bronica S2 chimney finder) wasn't easy, I better have a 7x or 8x loupe.
Anyway, there's indeed vignetting, but I don't know of course if it is ok with a Super 90mm at f8.
The Pro 105mm has a circle of 120mm, so I guess if this was that lens then there would be a much bigger vignetting than this. Yet there's this insane blur tunnel effect. Maybe the Pro 105mm does in fact cover quite more than 120mm but instead of going just black, with so much optical degradation that only 6x9 is usable?

[djdister]

Well, that shutter is not the right one for the lens, but I doubt that the front element is a "fake." Since the shutter is not right for the front element, the rear element could also be mismatched to the front element, leaving you with an unintentional Holga special.

[landstrykere]

well, I have some Frankenstein then...

[Dugan]

Make it your "signature" lens!
It can be your schtick!

[Greg]

Over the years have bought two view camera lenses off ebay which had the correct front set of elements and the correct shutter, but the rear set of elements was from another lens that just happened to screw into the rear of the shutter. Resulting images looked just like yours and didn't improve by all that much when the lenses were stopped down. Returned one for a full refund and an apology from the seller. From the other received a full refund, but the seller told me to just keep the lens... hunch was that he knew exactly what he had sold me. Have tried maybe 8 times to mismatched front and rear groups of elements. In every case the resulting Bokeh was just plain lousy.

[landstrykere]

well in this case it's my fault: I should have paid attention at the pictures provided by the seller. There were close-up of everything also the shutter wheel...
In fact the seller didn't know much about the gear, because I asked if the 90mm cam was installed on the bed, and he answered back "what is a cam?" so I went on yahoo.co.jp with google translate and found a page in japanese about these cameras, with description and pictures of the cam focusing system, sent the link to the seller. He answered back that a 105mm cam was installed.
So the seller offered a rebate, which was very useful because the price went a thin hair under the threshold for norwegian vat, so it spared me quite some money.
When I received the camera, indeed a 105mm cam was installed, but also the slots under the top, inside, had each a cam (a 65mm and the ... 90mm). Seller had no idea, I mean the guy was just reselling a camera without further clues.
But then I should have though of the lens specs. As I said my first technical camera so I guess my reflexes for close inspection of 35mm and MF stuff were off...

[reddesert]

It's not a "fake" in the sense of a counterfeit. The question is whether it's been modified inappropriately.

From the Horseman manual you linked, the 105/3.5 is a reversed Tessar design with one group in front of the aperture and two behind (the reversed aspect is surprising to me), and the 90/5.6 is a Plasmat with two groups in front of the aperture and two behind. You can shine a light into the lens from either side and count the reflections to count the groups. You can also tell whether the surfaces are convex or concave by seeing which way the reflection moves as you move the light.

The manual also gives the overall length of each lens. You can measure the length of the lens to see if it matches. Sometimes when lenses are re-mounted, the spacing is wrong and that can affect performance, especially off-axis.

The appearance and five-bladedness of the aperture doesn't seem wrong.

Usually, front and rear lens cells will unscrew from a shutter without needing a tool. Sometimes if they are tight, wrapping a rubber band around the front ring to get some extra friction will help.

[landstrykere]

You can shine a light into the lens from either side and count the reflections to count the groups. You can also tell whether the surfaces are convex or concave by seeing which way the reflection moves as you move the light.

The manual also gives the overall length of each lens. You can measure the length of the lens to see if it matches. Sometimes when lenses are re-mounted, the spacing is wrong and that can affect performance, especially off-axis.

I did write a duplicate of this issue on Photrio forum too, and Dan Fromm there advised to check the reflections. Which i did and find four strong but it's tricky about another weak one or not... Also I checked mechanical vignetting by looking at the groundglass corners from the front of the lens, wide open, and I can see all four corners on the 4x5 extender.
Length and weight were the first things I though of, length is ~39,60mm and weight ~225g, the 90mm lens is 220g and 40,5mm long as per manual and the 105 f3.5 240g, length of 90mm and 38mm.

So all in all quite possible it is the front of a 90mm with the shutter and the rear of a 105mm f3.5 .... could explain that there's no mechanical vignetting but optical aberrations after the 120mm circle...

I don't care so much about the use with the 4x5 extender on my Horseman 985, because anyway focus can't be done, with this Frankenstein I have, with the rails, but by moving the lens near the end of the rails and into the housing. I guess with the real 90mm, it would work with the rails.
The lens is otherwise very nice on 6x9 but my current concern is the focusing on the rangefinder, for 6x9 roll film. I have to adjust the rangefinder, it is off, but then if the 90mm I have isn't the real one, it may not be usable for calibration. I have another (good) lens, the recessed 65mm f7, but calibration is better done with a normal or portrait lens.
Anyway now I am buying a 105mm f4.5 (triple checking things with the seller...)

[landstrykere]

Sometimes when lenses are re-mounted, the spacing is wrong and that can affect performance, especially off-axis.

oh well, now I focus on this possibility. Because looking at pictures of 105mm f3.5 online besides the diagram in the manual, I see the rear element is very different than the one I have, which looks more like the 90mm.

mine:



a real Topcor 90mm (checked many onine listings):



a real Topcor Pro 105mm f3,5:



the rear element is clearly very different. much smaller on the 105f3,5.

so what I have may be a 90mm which shutter was broken and replaced with the shutter of a 105f3.5, but doing so, spacing may differ...

whatever it can be, so it is, nothing I can do unless I can grab a broken 90mm with working shutter and swap elements... The lens anyway performs very well on 6x9...

[Tin Can]

Don't forget to try each element separately, taking a pic of something that you like or a pattern

Some lenses can surprise and some were made for that

Aperture does change smaller

Break all rules, it's just a lens

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