Seeking Info About the B&H Projection Lens

[Bold]

B&H modification plan:

1. Remove front element from B&H front housing
2. Make a partial cast of the front housing using RTV silicone rubber
3. Make a black polyurethane cast from the RTV mold. Polyurethane is rated Shore D 75 (same rigidity & strength as a hard hat)
4. Get a M52 helicoid
5. Make a partial cast of the M52 helicoid
6. Make a polyurethane cast of the helicoid from the RTV mold
7. Measure, file, and sand both polyurethane parts, bond them together to create new front housing
8. Add B&H front element to M52 helicoid using rubber o-rings, screw helicoid into new front housing
9. Screw the final product into the B&H anamorphic housing. Pray that it works

Steps 1, 2, and 4 are complete.

Will attempt step 3 once the mold has set.

 

[Bold]

Getting the housing out without tearing the mold was tedious.  I must be more generous with the mold-release spray next time, or at least use a toothbrush to get the release agent into the threads more thoroughly. But it worked.

[Bold]

First attempt at casting polyurethane:

• When the label on the polyurethane mixture says working time is 1 minute, they ain't kidding.  I took way too long mixing & pouring, and the mixture lost viscosity so I was unable to fill the mold completely.
• Also, there was too much suction from the silicone rubber, getting the cast polyurethane out was really difficult

Second attempt at casting polyurethane:

• Tried a new mold to create the adapter in one piece instead of two.  Polyurethane mixture was poured quickly, and was really viscous.  So much that there was some leaking through small cracks in the mold.  I'll have to make the next mold completely airtight.
• Next time I really need to go overboard with the release agent (a spray that keeps the polyurethane from sticking to the mold).  Still a lot of difficulty getting the cast out of the mold - especially the M52 helicoid thread.  I finally had to crack the polyurethane to get it off.

But I tried the broken prototype screwed in smoothly:

If I turn it over it looks much better 

And it held firm when I rotated the helicoid

If I glue the broken pieces together I'd probably be good to go, but I'm determined to perfect this so I get a successful one-piece casting.  I'm also determined to create a mold that is a little more refined in its measurements, and a mold sturdy enough that I can produce multiple copies,

 

[Bold]

More adventures in novice polyurethane casting:

Another attempt to create a polyurethane housing looked promising, but the 52mm threads are too fine for the material.  The resulting thread impressions were too delicate, and screwing in the M52 helicoid tore up the polyurethane threading.  However, I realize a slightly different approach to casting directly onto the helicoid will result in a very tight seal with the 52mm threads, creating a permanent solution  But I must be more methodical and precise, otherwise the polyurethane will leak during casting, and gum-up the internal helicoid threads.

So no joy yet, but I feel a successful solution is getting closer.

[Frank Einstein]

does dis black puddin focus ta infinity, i read somwhere it did not, maybe you fix it, can u shares how now?

[Bold]

does dis black puddin focus ta infinity, i read somwhere it did not, maybe you fix it, can u shares how now?

In Nick's post, he said his (slightly different) modification could focus to about 40 feet, later in that thread John Barlow said he fixed this using a cemented 2-element negative achromat (BTW, if anyone knows which achromat he's talking about, please let us know).

Earlier in this thread Rich posted an screencap @ infinity with his helicoid mod, it seemed fine.  I measured the focus travel distance of the unmodded B&H...the front element moves approximately 4mm when you focus from closest to farthest.  The helicoid has a travel distance of approximately 14mm, so there's a lot more play with the modded focus.

Based on this & Rich's test photo, my guess is yes, the modded version of the B&H should be able to focus to infinity. Once my mod is done I will test & confirm.

[Gabriel Copoeru]

 

In Nick's post, he said his (slightly different) modification could focus to about 40 feet, later in that thread John Barlow said he fixed this using a cemented 2-element negative achromat (BTW, if anyone knows which achromat he's talking about, please let us know).

Earlier in this thread Rich posted an screencap @ infinity with his helicoid mod, it seemed fine.  I measured the focus travel distance of the unmodded B&H...the front element moves approximately 4mm when you focus from closest to farthest.  The helicoid has a travel distance of approximately 14mm, so there's a lot more play with the modded focus.

Based on this & Rich's test photo, my guess is yes, the modded version of the B&H should be able to focus to infinity. Once my mod is done I will test & confirm.

 

Hey Bold, I was thinking about your efforts on modding the B&H and I remembered another way to do it. I stumbled upon this guy selling a so called "single focus anamorphic" which actually is a modded B&H with the branding erased selling for a ridiculous price (it has been discussed on Nick's original thread). Thing is, on the bottom of the listing there is a video illustrating the mechanism of the mod that really attracted my attention. 

At one point I messaged him to ask about it and he responded that what he did was to have the front focus unit dremeled inside to smooth out the inner thread and insert a rubber O ring to have the unit slide instead of turning. Seems kind of tricky but the end result seems to be a less of a hassle than the polyurethane mold method you are trying (kudos to you for giving it a try, though, it would the most elegant solution if it works). What do you think?

Direct link to the video: http://filmhack.ro/portfolio/bh

 

[Bold]

Thanks Gabriel, I've seen that eBay listing.  Yeah the price is a ridiculous.  The focus appears to be push-pull, and I'm dead set on a solution that can work with a follow focus unit.  My last attempt was almost there. But the damned polyurethane is so viscous it found its way into the helicoid and locked it up.  I'm going to try soaking the helicoid in a solvent to loosen the polyurethane so I clean it out.  Failing that, I'll suck it up and order a new helicoid...

[Bold]

Question for Rich, et al:

J-oc's B&H is super cool but at $355 (plus shipping) the SK Grimes mod is more than I'm willing to spend. Yet the prospect of a 20-inch minimum focus is very appealing.  If I were to integrate a helicoid with a longer throw — say 30mm instead of the 14mm one I have — would that give my mod enough travel to get a closer focus like J-oc's?  

[Gabriel Copoeru]

Well, technically, yes. The further the front diopter travels, the closer focusing you get. You might get some vignetting, is all. 

[j-oc]

Jumping in here Boldy...

Question for Rich, et al:

J-oc's B&H is super cool but at $355 (plus shipping) the SK Grimes mod is more than I'm willing to spend. Yet the prospect of a 20-inch minimum focus is very appealing.  If I were to integrate a helicoid with a longer throw — say 30mm instead of the 14mm one I have — would that give my mod enough travel to get a closer focus like J-oc's?  

I don't see why not, providing it doesn't vignette. The other thing is that when you are focusing that close the depth of field is so tiny that the image will start to break down if you push it much closer than 20 inches or so.

I'm going to have to an hour or so after work tonight to play with this, so let me know if I measure something etc to help you out.

[Bold]

I stumbled upon this guy selling a so called "single focus anamorphic" which actually is a modded B&H with the branding erased selling for a ridiculous price

It's obvious this guy's been reading this thread, his latest offering now incorporates a helicoid.  I've considered selling one of my B&H's when I'm done and put on eBay for $100 less just to undercut him.  Although that would still make me a profiteering a$$hole.

However I would like to recoup some of my cost in materials and R&D.  What do you think is a fair asking price for a modded B&H? 

[Tito Ferradans]

Bold, I'm not sure everyone will agree - or even you - but selling one of yours for $100 just to undercut him doesn't make you a profiteering a$$hole. There is a HUGE difference between both cases, even if the lens is exactly the same: he is just sucking out the knowledge and making a profit. You gave the community back so much along these  threads that "fair price" is a very vague concept.

In my opinion, ours is such a niche market that the price can be adjusted according to supply and demand. Do you think $3k for an Isco is a fair price? I don't, but people are paying it anyway. All anamorphics are overpriced because there's too much interest in them and people are willing to pay. It's impossible to stop them and try to drive the prices down. It won't be you alone, selling a great mod for a low price that will change that. It's very likely that if you put the price too low somebody would grab it just to resell for profit. I won't lie: I've done it before because I needed the money and because an Isco for $1750 is very hard to pass.

So... what do you think of this?

[Gabriel Copoeru]

Bold, I'm not sure everyone will agree - or even you - but selling one of yours for $100 just to undercut him doesn't make you a profiteering a$$hole.

Actually he said $100 dollars less than that ebay hustler he metion, so it would still be quite above its value

On a more related note, I've decided to go the route of modding my BH to a push pull focus by dremeling the inner thread of the focus unit. It's barbaric, but I had no other choice as where I live there aren't any machinists that could build fine parts like a separate focus unit. 

Problem is I don't know what to do to make it slide back and forth easier.

[Nikkor]

Problem is I don't know what to do to make it slide back and forth easier.

Lubricant, my friend.

[Bold]

Lubricant, my friend.

This is probably the way to go, just use caution with the type & amount of lubricant — otherwise there's the risk of the lubricant getting onto the inner glass element when you push-pull.

And Tito to your point, I think the subject warrants its own thread 

[anti12]

Here is my sub $ 20,-- quick and very dirty push focus mod.
1. 60mm diameter 2mm thick 8cm long Aluminum Tube
2. Two step-up rings (49mm-52mm + 52mm-58mm) to hold the Front Lens.

Just jammed the Front-Lens inside the 49mm Ring with some Tape. (Maybe I will use Silicone to secure the Lens)
The 58mm End will hold the Lens-Assembly in Front of the Tube and is fixed there with Electrical Insulation Tape.
To slide and guide the Tube I taped some thin Packaging Foam around the Anamorphic Lens-Body.

 

[anti12]

ps My first attempt was to use Focus Bellows, but in order to achieve Infinity Focus the Anamorphic has to sit inside the Belows and mine was to small.

[Richie Recoil]

You can still get pretty solid results with this lens sans modification.  I've been reading this thread and plan to mod or hire someone to do it evenutally.  Of course rack focusing is out of the question, but for some applications in stock form it serves as a useful lens, especially when you factor in that you only have to focus the anamorphic.  

B&H 2x video shot on Panasonic G7: Anamorphic Boxing

[Bold]

Finally, a progress update.

A combination of polyurethane casting and 3D printing to mate the B&H anamorphic with the helicoid.

A couple 3D printed brackets to hold the front glass element in the M58 Helicoid.

Plus some invaluable help from a friend (with a workshop) for marrying the finderscope bracket with the 15mm rail system.  The helicoid pictured is 25mm-55mm, in hopes the longer travel distance will allow closer focus. I have a 17-31mm helicoid as a backup in case vignetting on the longer helicoid is too much.

This has been an agonizing process full of mis-steps.  Fortunately, no anamorphics were harmed in the making of this prototype.  Although two helicoids did not make it (RIP).  But I'm only a few days away from testing.  Everything fits snugly so I'm crossing my fingers that the test footage will be worth the absurd amount of time I've put into this.  I hope to have good news soon.