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**ChrisPlatt** · 12-27-2021, 05:42 PM

I bought a lot of filters.

Included is a Tiffen set of very recent manufacture,
UV, C-PL and 812, all marked 25mm, in a Tiffen nylon pouch.

Does anyone know what these tiny things fit?

TIA,
Chris

LowVoltage · 12-27-2021, 06:11 PM

I believe these are meant to be used in some kind of video application. One Google results shows these are part of a "video essentials" kit.

**AlwaysAl** · 12-27-2021, 07:00 PM

Had a Tokina 500 mm mirror lens once upon a time and it used filters mounted in the rear, towards the camera body. They were small (I think 25-35mm) and came in a three filter (leather pouch) kit along with a spanner to remove and install. Recall these were ND filters of varying grades.

**Digitalis** · 12-27-2021, 07:00 PM - **1 Like**

Some uncommon rangefinder lenses have filter diameters that small. Also these might be suited for telescopes.

---------- Post added 2021-12-28 at 12:32 PM ----------

Originally posted by AlwaysAl

Had a Tokina 500 mm mirror lens once upon a time and it used filters mounted in the rear,

A polarising filter would be a bit awkward to use in this instance...

stevebrot · 12-27-2021, 07:21 PM

Rear and internal filters?

Steve

**ChrisPlatt** · 12-27-2021, 07:30 PM - **2 Likes**

Tiffen has a webpage with a cross-reference for camera model and filter size.
25mm is not listed there, so I emailed Tiffen tech support to ask what they fit.

Their answer : "Any camera that has a lens with 25mm filter threads."

Chris

**K-Three** · 12-27-2021, 07:31 PM

Potentially some optics lab applications too?
Camera Filter Mount & Ring for 25mm filters (25.5mm male thread)

**AlwaysAl** · 12-27-2021, 08:37 PM

Originally posted by Digitalis

Some uncommon rangefinder lenses have filter diameters that small. Also these might be suited for telescopes.

---------- Post added 2021-12-28 at 12:32 PM ----------

A polarising filter would be a bit awkward to use in this instance...

Agreed, These filters weren't anything that was adjustable and, reflecting, assume these were to offset the fact the lens had a fixed, f8 aperture. Main reason I got rid of it; only seemingly worked well on bright sunny days.

**pentaxus** · 12-27-2021, 09:48 PM

Rear filters for a catadioptric lens.

wadge22 · 12-27-2021, 10:02 PM

Auto 110 24mm 2.8 (the normal lens for Auto 110 system)

Lhorn · 12-28-2021, 12:26 AM

Wadge beat me to it. 25mm is the filter size for one of the auto 110 lenses.

biz-engineer · 12-28-2021, 03:41 AM

Originally posted by ChrisPlatt

Does anyone know what these tiny things fit?

I think those filters are for kids under 10. How old are you?

**ChrisPlatt** · 12-28-2021, 03:42 PM

Originally posted by Lhorn

Wadge beat me to it. 25mm is the filter size for one of the auto 110 lenses.

The Pentax Auto 110 24/2.8 is listed as 25.5mm
I haven't measured but these are marked 25mm.

Chris

**ProfessorBuzz** · 12-28-2021, 07:14 PM

Perhaps a drone? There are a few with small filters around 1" in size.

12-27-2021, 05:42 PM	#1
ChrisPlatt Site Supporter Join Date: Nov 2007 Location: Rockaway Beach NYC Posts: 7,702	25mm thread filters? I bought a lot of filters. Included is a Tiffen set of very recent manufacture, UV, C-PL and 812, all marked 25mm, in a Tiffen nylon pouch. Does anyone know what these tiny things fit? TIA, Chris

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12-27-2021, 06:11 PM	#2
LowVoltage Veteran Member Join Date: Jul 2009 Location: Mount Joy, PA Photos: Gallery Posts: 544	I believe these are meant to be used in some kind of video application. One Google results shows these are part of a "video essentials" kit.

12-27-2021, 07:00 PM	#3
AlwaysAl Loyal Site Supporter Join Date: Mar 2007 Location: West GTA, Ontario, Canada Photos: Gallery \| Albums Posts: 555	Had a Tokina 500 mm mirror lens once upon a time and it used filters mounted in the rear, towards the camera body. They were small (I think 25-35mm) and came in a three filter (leather pouch) kit along with a spanner to remove and install. Recall these were ND filters of varying grades.

12-27-2021, 07:00 PM - 1 Like	#4
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,695	Some uncommon rangefinder lenses have filter diameters that small. Also these might be suited for telescopes. ---------- Post added 2021-12-28 at 12:32 PM ---------- Originally posted by AlwaysAl Had a Tokina 500 mm mirror lens once upon a time and it used filters mounted in the rear, A polarising filter would be a bit awkward to use in this instance...

12-27-2021, 07:21 PM	#5
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Rear and internal filters? Steve

12-27-2021, 07:30 PM - 2 Likes	#6
ChrisPlatt Site Supporter Join Date: Nov 2007 Location: Rockaway Beach NYC Posts: 7,702 Original Poster	Tiffen has a webpage with a cross-reference for camera model and filter size. 25mm is not listed there, so I emailed Tiffen tech support to ask what they fit. Their answer : "Any camera that has a lens with 25mm filter threads." Chris

12-27-2021, 07:31 PM	#7
K-Three Loyal Site Supporter Join Date: May 2014 Location: Pugetopolis, WA Photos: Gallery Posts: 938	Potentially some optics lab applications too? Camera Filter Mount & Ring for 25mm filters (25.5mm male thread)

12-27-2021, 08:37 PM	#8
AlwaysAl Loyal Site Supporter Join Date: Mar 2007 Location: West GTA, Ontario, Canada Photos: Gallery \| Albums Posts: 555	Originally posted by Digitalis Some uncommon rangefinder lenses have filter diameters that small. Also these might be suited for telescopes. ---------- Post added 2021-12-28 at 12:32 PM ---------- A polarising filter would be a bit awkward to use in this instance... Agreed, These filters weren't anything that was adjustable and, reflecting, assume these were to offset the fact the lens had a fixed, f8 aperture. Main reason I got rid of it; only seemingly worked well on bright sunny days.

12-27-2021, 09:48 PM	#9
pentaxus Site Supporter Join Date: Jun 2010 Location: Central Coast, CA Posts: 1,320	Rear filters for a catadioptric lens.

12-27-2021, 10:02 PM	#10
wadge22 Veteran Member Join Date: Jun 2021 Location: NE Ohio Photos: Albums Posts: 897	Auto 110 24mm 2.8 (the normal lens for Auto 110 system)

12-28-2021, 12:26 AM	#11
Lhorn Veteran Member Join Date: Jan 2019 Posts: 554	Wadge beat me to it. 25mm is the filter size for one of the auto 110 lenses.

12-28-2021, 03:41 AM	#12
biz-engineer Pentaxian Join Date: Feb 2015 Photos: Gallery Posts: 12,252	Originally posted by ChrisPlatt Does anyone know what these tiny things fit? I think those filters are for kids under 10. How old are you?

12-28-2021, 03:42 PM	#13
ChrisPlatt Site Supporter Join Date: Nov 2007 Location: Rockaway Beach NYC Posts: 7,702 Original Poster	Originally posted by Lhorn Wadge beat me to it. 25mm is the filter size for one of the auto 110 lenses. The Pentax Auto 110 24/2.8 is listed as 25.5mm I haven't measured but these are marked 25mm. Chris

12-28-2021, 07:14 PM	#14
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	Perhaps a drone? There are a few with small filters around 1" in size.

25mm thread filters?

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