Acetal Lens Caps

[B.S.Kumar]

Posted with moderator approval

Like most others on the forum, I am sick of poor quality OEM lens caps. Rather than simply moan about it, I have contracted with a manufacturer to make acetal lens caps. The caps will be molded out of LG Lucel, an engineering plastic similar to Delrin. The initial samples look great. They have ribs around the circumference for better grip. The top surface is recessed so that a label can be stuck on it. The lens cap size is embossed on the surface for better readability. Finally, there are vents around the inner circumference to let air escape while attaching or removing the cap.

Sizes will range from 30mm to 105mm, in 1 mm increments. Prices will vary according to size:
30~50mm 1,200 JPY (~12 USD / 11 Euro)
51~70mm 1,600 JPY (~16 USD / 14 Euro)
71~90mm 2,000 JPY (~20 USD / 18 Euro)
91~105mm 2,500 JPY (~25 USD / 22 Euro)
Shipping will be extra, via International ePacket service or optionally, EMS.

Since these caps will be molded, the cost of the molds means that not all sizes can be made right away. Therefore, I'd like to know from members which specific sizes would interest them most. Please choose the sizes in the poll. If you do not see a specific size please reply either on the forum, or send me an email at focusgma at gmail dot com.

Thank you.
Kumar

[Jac@stafford.net]

That seems to good to believe! LG Lucel is stable as far as I know. Unfortunately, the only caps I could use are larger than 105mm. :( I suspect that many LF photographers have the same situation.
.
But good for you for being there for the rest of us!

Oh, pictures of the product would be welcome.
.

[Bob Salomon]

If there are vents to let air escape can't they also let dust or moisture enter?

[B.S.Kumar]

Jac, larger than 105mm is certainly possible. Let me know what size you want, and I'll get the manufacturer to give me a quote.

Bob, Fujinon caps all have embossed ribs on the inner side that allow a small air space between the cap's inner circumference and the lens barrel and serve the same purpose.

Kumar

[Jac@stafford.net]

If there are vents to let air escape can't they also let dust or moisture enter?

In my modest experience vents also allow moisture to leave the underside. There are other places moisture can invade. Care remains the responsibility of the owner.

[B.S.Kumar]

So far, there are 3 members asking for 52, 58, 62, 67, 70 and 80 mm caps. No one wants smaller or larger sizes? Is everyone else satisfied with their lens caps? Is it worth going ahead with this project?

Kumar

[Tin Can]

I have a 'few' lenses and I thought I needed all kinds of caps. When I read of your project I went and checked. It turns out I am able to mix and match to fit everything as I only 'use' at most 2 at a time. If I am missing caps I store the lens on clean glass and cover with unexposed fixed out film.

The really big and unusual caps I make from odds and ends.

So I am not your best customer.

Sorry it seemed like a great idea, execution and price.


So far, there are 3 members asking for 52, 58, 62, 67, 70 and 80 mm caps. No one wants smaller or larger sizes? Is everyone else satisfied with their lens caps? Is it worth going ahead with this project?

Kumar

[B.S.Kumar]

I probably have a few more than your 'few' lenses :) They're all stored in a controlled environment. The ones that don't have proper caps have lids covering them. I have a box full of caps - and none of them will fit the lenses that don't have caps! Carrying those lenses out is troublesome, trying to find the right cap. And the sight of those lenses with lids instead of proper caps is what made me think of this project.

We have 2,978 active members. I'm sure at least some of their lenses need caps. I could get going with a particular size if I could get commitments for at least 40 caps of that size.

Kumar

[B.S.Kumar]

Here are a couple of low-res 3D renderings to show what the caps will look like. They'll be black, not multi-colored!
I'll be getting samples in a couple of weeks, and will post photos at that time.

152654152655

Thanks,
Kumar

[Peter De Smidt]

I've Ben on a trip. When I get home, I'll do some measuring. These sound like a great product .

[Paul Cunningham]

I've standardized on 67mm and 82mm filters, with step up rings attached where needed. 52mm and 58mm are also of interest (native sizes).

[Taija71A]

... If you do not see a specific size please reply either on the forum...

Kumar... I would definitely be in for the following 'additional' Larger Sizes:

93mm, 110mm, 112mm, 115mm & 122mm (*70mm and 80mm were already voted on... In the Poll).
--
I sincerely hope... That you are able to proceed with this very, worthwhile Project.
BTW, those 3D 'Renderings' are looking really good! :)
--
Thank-you. Best Regards, -Tim.

[Kirk Gittings]

Every lens I have is either 77mm or adapted to 77mm.

[Peter De Smidt]

These are slip on caps, right? So the size should be a little bigger than the filter threads?

[Jac@stafford.net]

These are slip on caps, right? So the size should be a little bigger than the filter threads?

Yes, slip on. Break out the calipers. I have been surprised by a reasonable assumption. :)

[Taija71A]

Correct. I previously e-mailed Kumar and asked him this very same question.
--
His exact response was:

"LF lens caps are generally slip-on types, so yes, we are speaking of the external diameter of the front of the lens."

[Vaughn]

Whatever the diameter is of the rear of a Fuji W 300/5.6.

[B.S.Kumar]

Thank you all for the encouragement.

Tim, I have noted the sizes you want, and will get them made.

Kirk, I have noted down the 77mm size. That is also the size needed for the Mamiya RB/RZ lenses, so ithis size ought to be a good seller.

Peter, measure the front diameter of the barrels of your lenses and put down your requirements. For those not owning calipers, an easy and accurate way to measure is to lay the lens barrel face down on a sheet of graph paper. Align at least two graph lines with the barrel's circumference, and draw a circle with a fine pencil. Measure the diameter of the circle.

Vaughn, Fujinon lens caps have the size embossed on the inner surface. If you don't have the measurements, I've sold this lens earlier, and I will ask the buyer to tell me the size.

Kumar

[Vaughn]

I'll measure it -- hard to believe I have been using it as my main lens for 20 years without a rear cap! It helps that I use a homemade case for it that provides extra protection for the rear element.

[Taija71A]

Whatever the diameter is of the rear of a Fuji W 300/5.6.

Vaughn, I believe that you would be looking for a 70mm ø Rear Lens Cap.
(*But, please 'double-check' this information with Kumar).

Thank-you! -Tim.

[Jim Andrada]

More than you probably wanted to know but

Acetal is the common name for a family of thermoplastics with the chemical name "PolyOxy-Methylene". Acetal is available in a general purpose
copolymer grade, a homopolymer version (Delrin ®), and several filled grades. Acetal provides high strength and stiffness, enhanced dimensional
stability, and is easy to machine. As a semi-crystalline material, acetal is characterized by a low coefficient of friction and good wear, high strength,
stiffness, dimensional stability, very low moisture absorption, good wear and abrasion resistance and a wide range chemical resistance.

Delrin is a Dupont version of Acetal with slightly different properties. Japanese companies love Delrin/Acetal and we used it for some extremely high precision gear trains. BUT our US customer made us use a different plastic and/or or limit the total amount per unit to XX grams or less because of its flammability. Its easy to machine, stable, low friction. All good. But the "flame and smoke" compliance guys for electrical equipment don't like it. It's not going to burst into flames on your lens or in your pocket, but in a fire large quantities can cause problems.

[Jac@stafford.net]

Does Acetal out-gas?

[Bob Salomon]

Does Acetal out-gas?

You mean if it is not burning? To be approved for flight on the Space Shuttle NASA burned a Linhof Aero Technika and a Rollei 6008. To qualify the type of internal wires on the Linhof had to be changed because the original wires would out gas in a fire. On the 6008 we had to stop using a silicon filled fuse in the battery as they didn't want to have little pieces of silicon sand free floating if they broke a fuse.

[B.S.Kumar]

Jim, thanks for the detailed description. I read up on the different kinds of POM and those are exactly the reasons for choosing it.

Jac, no, acetal does not out-gas. Your lenses (and mine) will be safe.

Kumar

[Jac@stafford.net]

Bob Salomon you are the fountain of information. Thanks for that.
.

[Peter De Smidt]

Sorry for the delay. Here's my wish list:

1 - 48mm
1 - 51mm
1 - 72mm
4 - 85mm
2 - 87mm
2 - 118mm

[B.S.Kumar]

I've compiled a list of lens cap sizes for Fuji lenses. I'll be making similar lists for Rodenstock, Schneider and Nikkor lenses, as well as older lenses - Zeiss, Voigtlander, etc. This is certainly not complete, and I'd be glad to have more data for other lenses. Just let me know here, and I'll add them to the chart.

10 days after I posted this on various forums, the order of preference according to the polls and messages I've received is:

1. 70mm - Most Fuji lenses use that size for the front cap.
2. 80mm - Almost all of them are for Mamiya RB / RZ lenses. The general complaint is that the spring on one side breaks, rendering the cap unusable.
3. 48mm - Mainly for the older Fuji lenses
4. 67mm
5. 62mm
6. 58mm
7. 52mm

Also, I think most users seem to have asked for front caps only! LF lenses need rear caps as well, and in many cases, the rear element is relatively less well-protected. Sometimes the element is almost flush with the barrel.

The manufacturer is sending me the final samples soon, and I will share photos here. In the meanwhile, please go through the list. If there are any errors, please let me know, and I would appreciate your input on other lenses.

Thanks,
Kumar

[Chauncey Walden]

Kumar, have you made any provision for those lenses where the center of the front element (stupidly!) protrudes past the filter ring? This would require a step inside to sit on the filter ring and keep the face of the cap above the lens.

[B.S.Kumar]

Yes, I have thought about it, and will make those kinds of caps as well. Unfortunately, I do not have any of those lenses in my collection. If members could contribute to this thread, listing such lenses and their outer diameter, I will start getting drawings and samples made.

Final samples of the 48mm size caps should be here by towards the end of the month.

Kumar