Helicoids for custom build

abruzzi · Jan 7, 2025

I have this idea to expand out my Horseman Convertible. It may be impossible, but I think I can build a 3D model that functions like the default lens board. To start with, I'd like to build a board for a 100 or 105 normal lens. I've got several that would work well like the Nikkor 105/3.5 or Fujinon CM-W 105/5.6. The challenge--since the camera is scale focused--is to find a helicoid I could mount the lens in that is marked (or can be marked) for distance.

The one new thing I found was made by Fotoman:

Pardon Our Interruption...

What I like about this is it already has distance and DoF scales on the helicoid. I asked them what the closest focusing a 105mm helicoid and they said 1.7m, which is a bit short. I'd be happy with one meter, but so far I haven't found anything else. However I have 2 questions:

1. Does anyone have experience with the Fotoman part?
2. What other helicoids are out there that I'm missing. Due to how it will be used it needs to be able to mount a Copal #0 shutter for the lens. I've seen an expensive Rodenstock helicoid, and I know there is a user here that builds custom cameras ( @dirkfletcher ) and frequenlty outfits them with 47mm SA on a helicoid. So what is that helicoid and can it be adapted for longer lenses (the Horseman has a 62mm which is plenty wide for me, so I need a normal--105mm--and a long lens--180mm Fujinon A)

ic-racer · Jan 7, 2025

Mercury has a number of options. If you go that route, maybe just get the whole Mercury universal camera that uses your Horseman film backs.

abruzzi · Jan 7, 2025

I don't see any helicoids for sale on their site? Also the whole thing looks 3D printed, which I generally have a low opinion of, based on my experience. Have you used them? are they smooth to turn, but stiff enough to hold position when you remove yout hand?

Light Capture · Jan 7, 2025

M65 and more rare M77 helicoids are the way to go. Quite precise. Lots of M65 kinds available on eBay.
17-35mm extension is the most common.
However, some attention needs to be paid to which one is purchased.
I had a good luck with ones advertised to be made out of brass and incorporated in working products (for helicoid surfaces, outside looks the same).
Brass version is well dampened and stays in place. Only fractionally more expensive. Aluminum helicoid versions have some play and they're not as smooth.
Disclaimer is that I didn't really try all of the available ones.
Scale would need to be DIY or 3d printed or laser etched. I do it 3d printed and it works quite well.

3d printing can be good or bad in quite a few aspects. Looks, functionality or durability. Material and the way it's done is very important.

I don't have a Horseman Convertible but have 80x80 Horseman and make lens boards for most other cameras with M65 thread for the M65 helicoid.
Provided that particular lens board can accommodate these thread sizes.
Also corresponding M65 threaded lens boards that mount into M65 helicoid.
That basically turns this assembly of lens board + M65 helicoid + M65 lens board into something like Linhof focusing device.

This way of doing it also enables moving the helicoid/lens assembly from one camera to another.

ic-racer · Jan 7, 2025

abruzzi said:
I don't see any helicoids for sale on their site? Also the whole thing looks 3D printed, which I generally have a low opinion of, based on my experience. Have you used them? are they smooth to turn, but stiff enough to hold position when you remove yout hand?

I was thinking of these, I have not used them. They are inexpensive to try.

abruzzi · Jan 7, 2025

Light Capture said:
M65 and more rare M77 helicoids are the way to go. Quite precise. Lots of M65 kinds available on eBay.
17-35mm extension is the most common.
However, some attention needs to be paid to which one is purchased.
I had a good luck with ones advertised to be made out of brass and incorporated in working products (for helicoid surfaces, outside looks the same).
Brass version is well dampened and stays in place. Only fractionally more expensive. Aluminum helicoid versions have some play and they're not as smooth.
Disclaimer is that I didn't really try all of the available ones.
Scale would need to be DIY or 3d printed or laser etched. I do it 3d printed and it works quite well.

3d printing can be good or bad in quite a few aspects. Looks, functionality or durability. Material and the way it's done is very important.

I don't have a Horseman Convertible but have 80x80 Horseman and make lens boards for most other cameras with M65 thread for the M65 helicoid.
Provided that particular lens board can accommodate these thread sizes.
Also corresponding M65 threaded lens boards that mount into M65 helicoid.
That basically turns this assembly of lens board + M65 helicoid + M65 lens board into something like Linhof focusing device.

This way of doing it also enables moving the helicoid/lens assembly from one camera to another.

Thanks. I'll have to measure--M65 should be doable, but M77 might exceed the space.

Let me pick you brain a bit to make sure I understand what I'm buying. I searched ebay for "m65 helicoid" and got a bunch from $30 to about $60. I'll pick one just as an example:

Pardon Our Interruption...

This would require as M65 flange on my lens board and would mount an M65 (copal #3?) on the front. There didn't seem to be any with M25 (Copal #0) adapters, but that should be available somewhere.screw an adapter on the front, then the C0 shutter into that. The helicoid ranges from 25mm to 55mm. So, if hypothetically the distance from the front of the homemade lens board is 25mm from the film plane, then I need an approximately 55mm spacer between the helicoid and the board or the helicoid and the lens to get me to 105mm for infinity.

That all seems pretty doable. The lens board will be 3D printed. (I'm fine with 3D printing on stationary parts, its just moving parts where I get skeptical.) I've modeled and printed simple lens boards. This might get a bit more challenging, but still doable. I do wonder about getting exact and whether I need to plan for a way to shim the setup to get it accurate (fortunately Horseman made a ground glass that fits the back of the Convertible so with a tripod I should be able to dial it in as long as I'm not ordering 3D printed parts a dozen times as I adjust .3mm here ot there.)

A little googling found me this formula:

1/focal length = 1/Distance to subject(mm) + 1/Distance to film(mm)

So, with the item linked above I get:

1/105 = 1/x +1/(105+30) = 472.5mm or 18.6 inches as the MFD. Which is probably way closer than I'd trust a scale focused sports finder based camera. It looks like I'd only need 15mm of helicoid to get a 105mm lens focused to just under a meter (840mm) which would be fine.

Sorry for the brain dump. I'm just thinking this through. Tell me if I'm missing anything in my thought process. It seems like Horseman intended to make this a interchangable lens camera but never sold enough to justify building other lenses. I quite like its size and simplicity. With two other lenses this would be the perfect travel camera for me, so if I can make something happen, that would be great.

abruzzi · Jan 7, 2025

ic-racer said:
I was thinking of these, I have not used them. They are inexpensive to try.

For the life of me, I can't find that on their page. Can you post a link to that page so I can have a closer look? At first glance it seems much larger than would fit on the Convertible, but I'd still like a close look. You're right, its pretty inexpensive, so its worth considering.

thanks.

blee1996 · Jan 7, 2025

I often use M65/M42 helicoids for custom builds. I typically do a Proof of Concept to figure out the extension needed, either handhold the lens or use cardboard tube and duct tape. Then you know the range for the M65/M42 helicoid. It is also useful to keep a set of cheap M65/M42 extension tubes of various length just in case.

There are Copal 0 (M32.5) to M65/M42 adapter plate available on eBay. Some vendors also offer custom drill hole size for M65/M42 plates.

But you also need to figure out the adaptation from M65/M42 to your Horseman Convertible, which I'm not familiar.

You might also want to check with Kumar, who sells large format stuff from Japan and he might have helicoids built for your camera.

ags2mikon · Jan 7, 2025

Even the 17 to 31mm would be 14mm travel right? I'm thinking of doing this on a pacemaker board for a 65mm lens. Good thread here.

ags2mikon · Jan 7, 2025

Let's not forget RAF camere for adapters too. His stuff is well made and he will do custom work too. At least he did for me one time.

abruzzi · Jan 7, 2025

The Horseman Convertible is a weird camera that is, for all intents and purposes, just a rectangular piece of metal that mounts a 6x9 graflok film holder in the rear and a flat board with a lens in the front. They only ever made a single lens--a 62mm ƒ5.6 that is quite nice, IME. The board and lens are a single unit, so I'd need to take some measurements of my existing setup and model it, but that seems doable. I don't have or want a 3D printer so I outsource the printing to an online source.

Below is a photo of the camera disassembled. Top is the lens board with half of the sports finder extended. Bottom left is the camera itself with the other half of the sports finder, and bottom right is the film back. In my 3D modeled lens board I may try to build a pull out frame for the sports finder, but if that too complicated, a standard shoe mount view finder will work too.

I measured the distance fromtop to bottom of the silver rectangle on the lens board and thats a bit over 72mm so the M65 will fit but the flange may need to be trimmed.

abruzzi · Jan 7, 2025

ags2mikon said:
Even the 17 to 31mm would be 14mm travel right? I'm thinking of doing this on a pacemaker board for a 65mm lens. Good thread here.

yeah, and 14mm is still closer than a meter which would be fine for this experiment.

the bigger on with 30mm will focus a 180mm lens to about 1.2m or a 150mm lens to .9m

So for testing I'll order one of each, eventually one for the 105 and one for a longer lens.

ic-racer · Jan 7, 2025

abruzzi said:
For the life of me, I can't find that on their page. Can you post a link to that page so I can have a closer look? At first glance it seems much larger than would fit on the Convertible, but I'd still like a close look. You're right, its pretty inexpensive, so its worth considering.

thanks.

This link is from thier "Store" site. Yes, I can't get to it from the other site either.

Universal View Lens Kit

To order a view lens kit, you will need to pick one out of the Mercury View Lens Database (a spreadsheet downloadable from this page). That document tells you which focus unit is required for your lens. Order the correct style here according to the focus unit listed there. Place your order...

mercuryworks.store

ags2mikon · Jan 7, 2025

I have a Graflex XL with a broken helicoid I may do. It is very light and all metal. Some of the old shoe mounted rangefinders might be helpful too.

Light Capture · Jan 7, 2025

abruzzi said:
Thanks. I'll have to measure--M65 should be doable, but M77 might exceed the space.

Let me pick you brain a bit to make sure I understand what I'm buying. I searched ebay for "m65 helicoid" and got a bunch from $30 to about $60. I'll pick one just as an example:

Pardon Our Interruption...

This would require as M65 flange on my lens board and would mount an M65 (copal #3?) on the front. There didn't seem to be any with M25 (Copal #0) adapters, but that should be available somewhere.screw an adapter on the front, then the C0 shutter into that. The helicoid ranges from 25mm to 55mm. So, if hypothetically the distance from the front of the homemade lens board is 25mm from the film plane, then I need an approximately 55mm spacer between the helicoid and the board or the helicoid and the lens to get me to 105mm for infinity.

That all seems pretty doable. The lens board will be 3D printed. (I'm fine with 3D printing on stationary parts, its just moving parts where I get skeptical.) I've modeled and printed simple lens boards. This might get a bit more challenging, but still doable. I do wonder about getting exact and whether I need to plan for a way to shim the setup to get it accurate (fortunately Horseman made a ground glass that fits the back of the Convertible so with a tripod I should be able to dial it in as long as I'm not ordering 3D printed parts a dozen times as I adjust .3mm here ot there.)

A little googling found me this formula:

1/focal length = 1/Distance to subject(mm) + 1/Distance to film(mm)

So, with the item linked above I get:

1/105 = 1/x +1/(105+30) = 472.5mm or 18.6 inches as the MFD. Which is probably way closer than I'd trust a scale focused sports finder based camera. It looks like I'd only need 15mm of helicoid to get a 105mm lens focused to just under a meter (840mm) which would be fine.

Sorry for the brain dump. I'm just thinking this through. Tell me if I'm missing anything in my thought process. It seems like Horseman intended to make this a interchangable lens camera but never sold enough to justify building other lenses. I quite like its size and simplicity. With two other lenses this would be the perfect travel camera for me, so if I can make something happen, that would be great.

Yes, That's the brass one. Shorter 17-31mm is perfect on 105mm lens. As you say it will focus closer than you can reliably zone focus.
Focusing helicoid is sized on the size of the rear cell. It needs to fit through the helicoid. Around 58mm is a safe size for M65 helicoid. Could squeeze in
I fully printed different focusing devices and modeled some helicoids but tiny variations in print quality would change the feel.
Most printers are better today but it's enough to have variation in filament that's only a couple of hundredths of a mm to change the dimension by that much and it's no longer the same feel you would want.
Material would have to have zero warping for this to be repeatable. At $20-30 it's not really worth 3d printing.
I can achieve it if it's one off in a few tries but making a quantity, it would be tough to equal machined one. In this case it's simply an issue with tolerance and amount of warping.
Plastics will usually have better damping characteristics if the whole system is designed the right way.
If you only make it a simple thread, it would be possible, lens would rotate though. There are some designs like that. If lens rotation isn't important to you, this is an option too.

It's the best to use the shortest possible helicoid as it could cause mechanical vignetting if the lens' rear cell is inset too far inside the helicoid.

abruzzi · Jan 7, 2025

ic-racer said:
This link is from thier "Store" site. Yes, I can't get to it from the other site either.

Universal View Lens Kit

To order a view lens kit, you will need to pick one out of the Mercury View Lens Database (a spreadsheet downloadable from this page). That document tells you which focus unit is required for your lens. Order the correct style here according to the focus unit listed there. Place your order...

mercuryworks.store

thanks. I suspect its too large for the Convertible though.

abruzzi · Jan 7, 2025

Light Capture said:
Yes, That's the brass one. Shorter 17-31mm is perfect on 105mm lens. As you say it will focus closer than you can reliably zone focus.
Focusing helicoid is sized on the size of the rear cell. It needs to fit through the helicoid. Around 58mm is a safe size for M65 helicoid.

I have a good collection of tiny lenses so size shouldn't be an issue, and I don't want to make this too big. I'd love to use my Nikkor-M 105/3.5 but I don't want to lose it for my other cameras, and they're uncommon and a bit pricey. I have a Fujinon CM-W 105mm that has an oversized front element but a pretty tiny rear. For a 150, I would probably use a Schneider Xenar 150/5.6 its even tinier than the Fuji 105.

Dan Fromm · Jan 7, 2025

Interesting. Since your modified Convertible will have no movements, you don't need lenses that cover much more than 100mm. All of the lenses you mentioned are overkill. A 100/4.5 Ektar is probably all the normal lens you need.

ags2mikon · Jan 7, 2025

Or use the 105mm f3.5 Horseman and keep it all in the family.

abruzzi · Jan 7, 2025

Dan Fromm said:
Interesting. Since your modified Convertible will have no movements, you don't need lenses that cover much more than 100mm. All of the lenses you mentioned are overkill. A 100/4.5 Ektar is probably all the normal lens you need.

very true, but I do want to stick with a very modern shutter, partly for reliability, but also because it makes this easier to assemble. I just ordered some parts to begin the test, so I ordered a M65 helicoid, but I was also able to order a M65 to Copal 0 adapter, that is sized and threaded to mount copal 0 without a retaining ring. Finding similar for a Supermatic shutter is probably less likely.

I could also use a 100mm Symmar-S I have. I also have a number of other older lenses I could try out like a 105mm Georg Leitmeyr München Weitwinkel Anastigmat in a Prontor #0 or a 105mm Xenotar (its more complicated since it in a Compur #1.) Some of these are in modern shutters, some older but all are sized to the copal/compur standards which simplfies things. These are also all lenses I already have and don't require additional costs. The only Kodak lens I have in the 100mm vicinity is the WF Ektar, which I want to keep availalbe for my light weight 4x5 kit.

For anyone that want to follow along:

I measured the distance from the film plane outside surface of the factory lens board and its about 30mm (I don't have an easy way at the moment to measure it precisely.) So I ordered the following item from eBay sellers:

https://www.ebay.com/itm/255027713505 Helicoid - 17mm at the shortest.
https://www.ebay.com/itm/394637816375 M65 flange - probably adds 1mm at most.
https://www.ebay.com/itm/264297271795 39mm M65 extension
https://www.ebay.com/itm/256254685966 M65 to Copal #0 from the looks it adds 5-6mm

so 30+17+1+39+5 = 92mm

whatever additional is needed I'll make up be flaring the board. 13mm is small and shouldn't impact the ability to handhold easily.

EDIT: I forgot to mention that with all of the above I'm now in US$120. The lens could cost anywhere from US$100-$500 depending on which one ends up on this. I expect each print of board will cost about US$25 or so. Hopefully I only need a couple to get it right.

abruzzi · Jan 7, 2025

ags2mikon said:
Or use the 105mm f3.5 Horseman and keep it all in the family.

Actually, I forgot about that one, and I actually have it alsong with the slower Horseman 105/5.6. Unfortunately, the 105/3.5 it actually prettty big--not huge, but compared to the 105/5.6 its noticable.

Chuck1 · Jan 7, 2025

The 4.5 is a big chunk of glass

abruzzi · Jan 8, 2025

Chuck1 said:
The 4.5 is a big chunk of glass

yeah, I was working from memory which is a bad idea for me these days. There are 2 Horseman 6x9 105mm lenses--an ƒ3.5 and an ƒ4.5, and it is the ƒ4.5 that is large, not the ƒ3.5. The difference it probably because the ƒ4.5 has a 158mm image circle while the ƒ3.5 only covers 125mm.

ags2mikon · Jan 8, 2025

I also bought one of those m65 flanges and it was 5mm or 3/16" thick. If you use a tessar type of lens your back focus will be shorter than a plasmat type. IIRC. Please share pictures.

Light Capture · Jan 8, 2025

abruzzi said:
very true, but I do want to stick with a very modern shutter, partly for reliability, but also because it makes this easier to assemble. I just ordered some parts to begin the test, so I ordered a M65 helicoid, but I was also able to order a M65 to Copal 0 adapter, that is sized and threaded to mount copal 0 without a retaining ring. Finding similar for a Supermatic shutter is probably less likely.

I could also use a 100mm Symmar-S I have. I also have a number of other older lenses I could try out like a 105mm Georg Leitmeyr München Weitwinkel Anastigmat in a Prontor #0 or a 105mm Xenotar (its more complicated since it in a Compur #1.) Some of these are in modern shutters, some older but all are sized to the copal/compur standards which simplfies things. These are also all lenses I already have and don't require additional costs. The only Kodak lens I have in the 100mm vicinity is the WF Ektar, which I want to keep availalbe for my light weight 4x5 kit.

For anyone that want to follow along:

I measured the distance from the film plane outside surface of the factory lens board and its about 30mm (I don't have an easy way at the moment to measure it precisely.) So I ordered the following item from eBay sellers:

https://www.ebay.com/itm/255027713505 Helicoid - 17mm at the shortest.
https://www.ebay.com/itm/394637816375 M65 flange - probably adds 1mm at most.
https://www.ebay.com/itm/264297271795 39mm M65 extension
https://www.ebay.com/itm/256254685966 M65 to Copal #0 from the looks it adds 5-6mm

so 30+17+1+39+5 = 92mm

whatever additional is needed I'll make up be flaring the board. 13mm is small and shouldn't impact the ability to handhold easily.

EDIT: I forgot to mention that with all of the above I'm now in US$120. The lens could cost anywhere from US$100-$500 depending on which one ends up on this. I expect each print of board will cost about US$25 or so. Hopefully I only need a couple to get it right.

39mm extension will likely cause vignetting. 3d printing a lens board with a cone that attaches directly to the helicoid is a solution for this.
Ideally, helicoid should be as shallow as possible.

Helicoids for custom build

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