[kaseki]

I have sent a message to Ricoh-Imaging in the USA using their contact form. I await their answer with bated breath.

[kaseki]

...

"Ricoh Imaging accessories for both PENTAX and RICOH products can be purchased from any Authorized Ricoh Imaging Dealer."
[list of dealers ~ 100]
"Please Note: With regards to accessories and products that are not typically carried as in-stock inventory. These items can be ordered from any of our Ricoh Imaging Authorized Dealers."
...

I guess this means those of you hanging onto the underside of the earth will have to deal with your own nation's authorized dealers, although something could be worked out if a 'Merkin dealer cooperates and Oz dealers don't.

It also reminds me that a list of all possible accessories should be available. The possibilities might approach endless if we had one.

I'll call B&H when they reopen and see if they will place an order and I'll keep this thread posted with saga updates.

Sunday update: B&H Chat will contact their buyer when he is in on Monday to determine filter holder availability. The plan is to email me with a result.

Also, https://pentax.com.au/accessories/filters shows the filter holder to be in stock @ 172. AUD (presumably). Even pricier than the 80. BPS price.

(((Noticed while searching: two (one demo) DFA645 25mm lenses for sale in Norway: http://fovi.no/objektiv/pentax-645-fatning)))

[kaseki]

While awaiting a response from B&H, it occurred to me that if the "filter holder frames" needed for fast swapping of filters prove to be unobtainable, or restricted to repair/replacement, fabrication of a suitable alternative could be a project for 3D printing. Significant simplification could be applied assuming that each potential user already has a filter holder with rotation capability -- only needed for the circular polarizer.

The 3D-printed units could dispense with filter rotation, eliminating the knurled control, three gears, and whatever spindles and such lurk inside the plastic. A solid frame could be used with a 40.5-mm inside thread. Alternatively, one or more step-down rings could be obtained and locked down to get a metal 40.5-mm thread. For the 645DFA 25-mm lens, the filter axial position may be moderately important, so care would be needed to get the provided mating thread in the correct position. The DA 650mm may be more forgiving in that respect, as the filter is behind all the curved glass.

A means of attachment to the lens body would still be needed. I'm not sure much simplification is possible there, but the basic parts appear straightforward. Variation to avoid patent infringement, if applicable, should be possible.

---------- Post added 22nd Feb 2021 at 13:12 ----------

With respect to @mikeSF's comments hereinbefore, what are the advantages of using an ND filter over operating the camera in the multi-exposure composite mode?

[angerdan]

... fabrication of a suitable alternative could be a project for 3D printing.

Sounds interesting. But how about the needed precision for the filter thread?

[kaseki]

Sounds interesting. But how about the needed precision for the filter thread?

While I don't know the latest in precision of 3D parts, I think the thread precision could be good enough to screw in a step-down ring once, and then use the inner step-down ring thread for filter changes. It is also possible to have a not quite interference fit between a cylindrical wall and the outer part of the step-down ring, and a bit of epoxy for retention. Or drill and tap a set screw hole half way into the frame and half way into the step-down ring. Or tap the 3D assembly with an outer step-down ring thread form tap. A mechanical designer could come up with several options of varying cost.

I would want a few of these holder frames for the few filters that I could conceive of using so that I could minimize time and lens guts exposure. In such a case, there wouldn't need to be a lot of action on the filter threads. Assume brass ring filters to minimize grab on the step-down ring or whatever thread material is used.

[kaseki]

Update: It has been a week since I chatted with B&H. Other than sending me a copy of the chat log, there has been no response to my request.

[Ed Hurst]

My experience (admittedly a few years ago) in Australia was very similar - the question just vanishes into a black hole. I really think, if you have found a Pentax operation elsewhere in the world selling this item, your best (maybe only) bet is to order it directly from them. There may be difficulties in doing that, not to mention paperwork and cost in shipping, tax, etc.. But if it works with difficulty, that may be better than not working at all. Of course, if you find another way, I take my hat off to you :-).

[Frank Michael]

Hello at all:

First, i was a few Years away from this Forum, must earn money with my Camera work.

Last Week i made a visit, read the thread about the filter Holder....BANG. 4 years ago i made a reservation for an originall Filter holder for my DFA 25mm, nothing happend, black hole and silence in Japan and Germany.

I ordert last week the Holder for the 560mm, yesterday i got a message from UPS, its on the truck, will arrive Monday.

Tuesday i will give you an answer, if its working... or not. And Pictures. THANK YOU fot the Tipp , Kaseki

best regards,

Frank

[kaseki]

Hello at all:

First, i was a few Years away from this Forum, must earn money with my Camera work.

Last Week i made a visit, read the thread about the filter Holder....BANG. 4 years ago i made a reservation for an original Filter holder for my DFA 25mm, nothing happend, black hole and silence in Japan and Germany.

I ordert last week the Holder for the 560mm, yesterday i got a message from UPS, its on the truck, will arrive Monday.

Tuesday i will give you an answer, if its working... or not. And Pictures. THANK YOU fot the Tipp , Kaseki

best regards,

Frank

Thanks. I think initial credit goes to angerdan. From which source did you order it, the EU, GBR, or AU?

With respect to communication with B&H Photo, I sent a reminder and got another case number referencing the first case number.

[itshimitis]

Hey guys and girls, just wondering if any of you have insights into using a Internal ND filter on the 25mm lens. If anyone could give me a link to where I can find some that would be great.

Thanks, Tom

Some years ago I got some Dörr filters. I got a 3 stop and a 10 stop. They need to be thin enough to fit on the mechanism. These were..

[Frank Michael]

Hello Kaseki,

i order it from EU.

regards

Frank

[kaseki]

Some years ago I got some Dörr filters. I got a 3 stop and a 10 stop. They need to be thin enough to fit on the mechanism. These were..

I should mention an optical factoid. On the 25mm, the filter is inside the optical train, and its optical thickness matters. Optical thickness = physical thickness times index of refraction. Optical thickness should mimic that of the supplied CP or supplied clear glass filler. Testing I reported here somewhere shows that in the extreme case of no glass filler, the optical behavior is to show a degraded focus. We don't have data as far as I know of what the index is that we should be matching, but if MikeSF finds the result satisfactory with the ND he specified, then that is at least one example of a suitable filter.

In the case of the 560mm, I believe the filter is behind the optical train. Changes in optical thickness there will only change the back focus, which usually can be compensated with the lens focus mechanism.

[Frank Michael]

Hello,

no fear, i will try it out. I use Heliopan ND- Filters for the original Filter Holder. Works great with NO optical degratation or any focus shift. Without any Filter.... no chance for a good Picture (logical!).

So stay tuned.

If the filterholder didnt meet expactations, i can send it back easy.

Regards

Frank

[Ed Hurst]

Hello at all:

First, i was a few Years away from this Forum, must earn money with my Camera work.

Last week, I made a visit, read the thread about the filter Holder....BANG. 4 years ago i made a reservation for an original Filter holder for my DFA 25mm, nothing happened, black hole and silence in Japan and Germany.

I ordered last week the holder for the 560mm, yesterday i got a message from UPS, its on the truck, will arrive Monday.

Tuesday i will give you an answer, if its working... or not. And Pictures. THANK YOU for the tip

best regards,

Frank

If the holder you receive this way fits the 25mm lens and works well, then I'll be eternally grateful! I'm one of the rare people in the world who already owns two holders - because I had a 25mm lens break years ago and replaced it (and kept the holder from the broken lens)... However, it would still be useful to have more than two.

[Frank Michael]

Hello at all 25mm Users:

YIIPPEJAAYEAH !

The UPS Truck arrived me, the filter Holder fits (!) perfect, same dimensions, absolut. And the white Paint looks noble :-))

Pictures will follow this day.

best regards

a happy franconian Frank