Full spectrum cut filter

Riggson · 10-10-2021, 12:27 PM

Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here.

I'm building up a camera based on the Raspberry Pi system and happened to find out the UV/IR cut filter is in the mount rather than bonded to the sensor. This would make having a full spectrum camera trivial as one could just omit the filter during assembly.
The lens I intend to use accepts 30.5 mm filters but outside of a couple offerings on AliExpress I don't find any UV/IR cut filters in this size. I can use a 37mm filter with a step up ring but would like to keep the smaller form. Has anyone come across a cut filter in the 30.5mm size?

Kobayashi.K · 10-11-2021, 05:29 AM

I gave Heliopan a look and they have one UV/IR cut filter size 30.5 x 0.5 in their price list, part nr. 1530 [1]. Heliopan has exactly one step-up ring 30.5 x 0.75 to 37mm, but several others with a 30.5 x 0.5 thread [2]. It looks the 30.5 filters mostly have a 0.5 mm thread pitch.

Heliopan
http://www.heliopan.de/wp-content/uploads/Preisliste.pdf
[1] For UV/IR cut filters see table 'Digital-Filter UV-/Infrarot-Sperrfilter'.
[2] For step-up rings see table 'Zwischenringe – Reduzierringe – Adapterringe'
Notice that some rings go up to a thread with 0.75 pitch and others have 0.5 on both sides.

**Bob 256** · 10-11-2021, 07:50 AM

Are you after a UV/IR cut filter? That would be your intention if you remove the sensor filter and still want to use the sensor normally (non-UV/IR). If you're intent is to make an IR or UV sensitive camera, then you want an IR or UV pass filter for the lens. That might be easier to come by in the size you're after (and is probably less expensive than an interference type UV/IR blocking filter).

On the other hand, if your intention is to use the sensor normally without its internal blocking filter, an external filter can be most any size with a filter size adapter. One issue you might run into, is if the lens is a wide angle, the edges of the lens's view may have somewhat different filtering since shooting through an interference filter at an angle changes its characteristics.

UV/IR Blocking filter:
https://www.bhphotovideo.com/c/product/800541-REG/Heliopan_730566_30_5mm_Inf...7bb163d5f6eff7

IR Pass filter (needed for IR photography):
https://www.ebay.com/itm/332881312900?chn=ps&_trkparms=ispr=1&amdata=enc:1H0...78e5e6d3ff9a23

Finding a UV pass filter (for UV photography) is going to be a lot more difficult. Marlin P Jones has a couple of unmounted UV filters (42 and 25mm) which might work though I don't know what their optical quality is and they aren't very far into the UV spectrum. These also pass some IR so that's another issue. Also, your lens itself must pass UV - some don't do so well at that.
https://www.mpja.com/365nm-UV-Pass-Filter-42mm-Diameter/productinfo/35587+MI/

zapp · 10-11-2021, 09:06 AM

30.5 mm is a regular format. Check Heliopan, Schneider, … on B&H, Edmund optics…

10-10-2021, 12:27 PM	#1
Riggson Junior Member Join Date: Nov 2017 Posts: 34	Full spectrum cut filter Staff note: This post may contain affiliate links, which means Pentax Forums may earn a small commission if a visitor clicks through and makes a purchase. If you would like to support the forum directly, you may also make a donation here. I'm building up a camera based on the Raspberry Pi system and happened to find out the UV/IR cut filter is in the mount rather than bonded to the sensor. This would make having a full spectrum camera trivial as one could just omit the filter during assembly. The lens I intend to use accepts 30.5 mm filters but outside of a couple offerings on AliExpress I don't find any UV/IR cut filters in this size. I can use a 37mm filter with a step up ring but would like to keep the smaller form. Has anyone come across a cut filter in the 30.5mm size?

10-11-2021, 05:29 AM	#2
Kobayashi.K Veteran Member Join Date: Mar 2013 Photos: Albums Posts: 716	I gave Heliopan a look and they have one UV/IR cut filter size 30.5 x 0.5 in their price list, part nr. 1530 [1]. Heliopan has exactly one step-up ring 30.5 x 0.75 to 37mm, but several others with a 30.5 x 0.5 thread [2]. It looks the 30.5 filters mostly have a 0.5 mm thread pitch. Heliopan http://www.heliopan.de/wp-content/uploads/Preisliste.pdf [1] For UV/IR cut filters see table 'Digital-Filter UV-/Infrarot-Sperrfilter'. [2] For step-up rings see table 'Zwischenringe – Reduzierringe – Adapterringe' Notice that some rings go up to a thread with 0.75 pitch and others have 0.5 on both sides. Last edited by Kobayashi.K; 10-11-2021 at 06:00 AM.

10-11-2021, 07:50 AM	#3
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Are you after a UV/IR cut filter? That would be your intention if you remove the sensor filter and still want to use the sensor normally (non-UV/IR). If you're intent is to make an IR or UV sensitive camera, then you want an IR or UV pass filter for the lens. That might be easier to come by in the size you're after (and is probably less expensive than an interference type UV/IR blocking filter). On the other hand, if your intention is to use the sensor normally without its internal blocking filter, an external filter can be most any size with a filter size adapter. One issue you might run into, is if the lens is a wide angle, the edges of the lens's view may have somewhat different filtering since shooting through an interference filter at an angle changes its characteristics. UV/IR Blocking filter: https://www.bhphotovideo.com/c/product/800541-REG/Heliopan_730566_30_5mm_Inf...7bb163d5f6eff7 IR Pass filter (needed for IR photography): https://www.ebay.com/itm/332881312900?chn=ps&_trkparms=ispr=1&amdata=enc:1H0...78e5e6d3ff9a23 Finding a UV pass filter (for UV photography) is going to be a lot more difficult. Marlin P Jones has a couple of unmounted UV filters (42 and 25mm) which might work though I don't know what their optical quality is and they aren't very far into the UV spectrum. These also pass some IR so that's another issue. Also, your lens itself must pass UV - some don't do so well at that. https://www.mpja.com/365nm-UV-Pass-Filter-42mm-Diameter/productinfo/35587+MI/ Last edited by Bob 256; 10-11-2021 at 11:03 AM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K-5 Full spectrum conversion (IR filter removal)	Azergoth	Do-It-Yourself	21	03-20-2024 04:03 AM
For Sale - Sold: Full Spectrum K-01	HomeMadeSin	Sold Items	7	07-02-2021 06:51 PM
Landscape "Saguaro" K-01 Full Spectrum Converted	rosettaquarrier	Post Your Photos!	20	12-25-2019 07:59 AM
For Sale - Sold: Pentax K-30 + Full Spectrum	HomeMadeSin	Sold Items	2	11-07-2019 09:00 PM
Cut,cut cut and cut	shooz	General Talk	31	02-21-2011 12:34 PM

10-11-2021, 09:06 AM	#4
zapp Pentaxian Join Date: Jul 2011 Posts: 2,385	30.5 mm is a regular format. Check Heliopan, Schneider, … on B&H, Edmund optics…