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11-21-2017, 04:32 AM   #1
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Pentax Normal 40.5mm Filter (for rear filter holder of DA 560mm and 645 DA 25mm)

Hello guys,

i'm looking for a source and price of the filter included in the DA 560mm filter holder. Any ideas?
No need for CP-L or ND. Also i know there are UV filters for 40.5mm, but no information about the original Pentax normal 40.5mm filter.

Here's how the filter looks like:


11-21-2017, 07:14 AM   #2
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Not Pentax, but here's a possible solution:

Nikon 40.5mm NC Neutral Clear Filter
11-21-2017, 07:59 AM   #3
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Thanks, i guess a high quality third-party filter will be as good as the original and wouldn't cost more.

So these clear/protect filters available for 40.5mm would be a good option:
And thats just the clear/neutral protection filters, UV filters would be fine as well.

Last edited by angerdan; 11-21-2017 at 06:05 PM.
11-21-2017, 10:33 AM   #4
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What is the included filter? If it's a clear/protective filter, what does it protect inside the lens?

11-21-2017, 11:43 AM   #5
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QuoteOriginally posted by leekil Quote
What is the included filter? If it's a clear/protective filter, what does it protect inside the lens?
The default - clear - filter is included simply because the filter is part of the optical design.There was a comparison a while back made with a Tamron 300/2.8, and the author claimed the image with the clear filter was slightly sharper than the image without it.

Last edited by luftfluss; 11-21-2017 at 11:51 AM.
11-21-2017, 04:09 PM - 1 Like   #6
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https://www.schneideroptics.com/pdfs/filters/405.pdf

The optical formulas are designed to have a filter in place which is why you get better performance with the "blank" in place than without.
11-21-2017, 05:52 PM   #7
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QuoteOriginally posted by luftfluss Quote
The default - clear - filter is included simply because the filter is part of the optical design.There was a comparison a while back made with a Tamron 300/2.8, and the author claimed the image with the clear filter was slightly sharper than the image without it.
Be careful

It is widely discussed that the first version of the tamron 300/2.8 adaptall lend had the filter forgotten in the optical design. The last 2 versions did not. Performance of the first version is better without the filter, the later versions better with the filter.

Also be careful about the thickness of the filter ring my tamron 200-500/5.6 requires a thin filter to fit in the holder and slide into the lens properly. Not all 40.5 mm filters are created equal
11-21-2017, 07:02 PM   #8
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QuoteOriginally posted by Lowell Goudge Quote
Be careful

It is widely discussed that the first version of the tamron 300/2.8 adaptall lend had the filter forgotten in the optical design. The last 2 versions did not. Performance of the first version is better without the filter, the later versions better with the filter.

Also be careful about the thickness of the filter ring my tamron 200-500/5.6 requires a thin filter to fit in the holder and slide into the lens properly. Not all 40.5 mm filters are created equal
Huh, I never knew that about the 107B.

Fortunately, both my 360B and 31A have the oem rear filters.

11-21-2017, 07:10 PM   #9
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QuoteOriginally posted by angerdan Quote
Thanks, i guess a high quality third-party filter will be as good as the original and wouldn't cost more.

So these clear/protect filters available for 40.5mm would be a good option:
And thats just the clear/neutral protection filters, UV filters would be fine as well.
You might want to send an email to Lensrentals.com and inquire about the filter. support@lensrentals.com I don't think they could sell you one, but being that they repair lenses and do rent a small amount of Pentax equipment, they might know where you could procure the genuine Pentax filter.
11-22-2017, 06:19 AM   #10
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I would go for the Hoya filter, 40.5 is an old Leica size and several makers still manufacture it, I looked some ten years ago for such a size in Pentax but nobody stocked them, I needed it for a 400-800 Zoom mirror lens, and the instructions for that stated a filter should be used at all times, I purchased my zoom second hand and the filter kit was missing, you might find one on ebay if your lucky.
12-02-2017, 03:39 AM   #11
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Finally i got a (used) B+W X-PRO UV for around 20 bucks.
It adds a "Made in Germany" touch to the lens configuration

Last edited by angerdan; 12-10-2017 at 05:26 AM.
08-10-2019, 05:24 AM   #12
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QuoteOriginally posted by angerdan Quote
Finally i got a (used) B+W X-PRO UV for around 20 bucks.
It adds a "Made in Germany" touch to the lens configuration
I picked up one of those yesterday, new, for the big bucks, and removed the filter cover to install it only to find that parts were rattling around inside the lens. The derned thing had come apart in there. I managed to fish out the geared and threaded ring with the original UV filter in it without any damage (I hope, fingers crossed).

I unscrewed the original filter but the threads of the new one would not mate with those on the ring. I couldn't see how to install the ring into the filter housing, anyway (other than the superglue solution). There doesn't seem to be any mechanism to hold the geared ring in place within the housing, with or without the filter. Trying to insert it, the whole thing just falls apart.

Anybody have any idea how that's supposed to work, or what parts are supposed to be there?

Maybe there's something still lost inside the lens?
08-11-2019, 02:26 PM   #13
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QuoteOriginally posted by dlh Quote
I picked up one of those yesterday, new, for the big bucks, and removed the filter cover to install it only to find that parts were rattling around inside the lens.The derned thing had come apart in there.

I unscrewed the original filter but the threads of the new one would not mate with those on the ring.
Anybody have any idea how that's supposed to work, or what parts are supposed to be there?
Oh, that sounds as bad as unusual.
First here are two pictures of the rear filter holder (one with and one without filter):
Filter Halter für das DA 560 mm Objektiv - RICOH IMAGING DEUTSCHLAND GmbH

Please post a picture of your filter holder or describe what's missing.
08-12-2019, 03:38 AM   #14
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QuoteOriginally posted by angerdan Quote
Oh, that sounds as bad as unusual.
First here are two pictures of the rear filter holder (one with and one without filter):
Filter Halter für das DA 560 mm Objektiv - RICOH IMAGING DEUTSCHLAND GmbH

Please post a picture of your filter holder or describe what's missing.
Thanks for the pictures. This was definitely a "shouldn't happen situation", but I think it probably occurred in the store rather than the manufacturer. As this is a brand-new lens, I hadn't tried to fish out the circular polarizer that came with the thing as yet, but yesterday I decided to take another look at the whole thing. When I looked in the pocket inside the case for the polarizer, I discovered that it was screwed into the "missing part". I suppose it was too hard to unscrew the polarizer given the rotation inherent thereto, and the whole part got unscrewed and put away as if it were supposed to have been like that.

Reminds me of the time when, as a curious little kid, I took apart the family's (mechanical, analog) alarm clock to see how it worked. A big brass thing with two bells on top. Since I couldn't figure out how any two pieces went together after having dissembled it, I shoved it all back in the case as separate pieces. When they figured out why the clock didn't work anymore, I received the consequences of my actions. I think something similar happened with this filter holder.

It appears that no harm was done, and the problem's solved. The pictures helped me know what it was I was looking for - thanks again.
08-12-2019, 10:53 AM   #15
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QuoteOriginally posted by luftfluss Quote
The default - clear - filter is included simply because the filter is part of the optical design.There was a comparison a while back made with a Tamron 300/2.8, and the author claimed the image with the clear filter was slightly sharper than the image without it.
Actually this is not quite correct.

The first version of the Tamron 300/2.8 had the optical design done without considering the filter, and version 1 lenses were actually sharper without the filter, the second and later versions were done with the filter included in the optical path, and were sharper with the filter.

The issue is that although the light travelling through the filter is almost parallel, the nominal ~250-500 micron filter thickness does distort (bend) slightly the light path, if not considered and corrected for .
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