Km IR filter cut-off

mvecchi · 09-09-2010, 09:20 PM

Hi all!!

Does anyone know at what wavelength the IR filter in front of the sensor cuts in? Anyone have a specta for the filter?

Cheers,
Mario

Adam · 09-10-2010, 09:00 AM

There are 720nm and 900nm filters, the former being the more common, AFAIK.

Edit: are you referring to the filter on the sensor itself rather than that on the lens? AFAIK, the one on the sensor cuts away all IR wavelengths. It will have to be removed if you want to do true IR photography.

RioRico · 09-12-2010, 09:22 AM

Various IR-pass filters are available. I use 780nm, 900nm, 930nm and 1000nm filters on my 5mpx Sony DSC-V1 'NightShot' P&S, which has a switch to flick-sway the IR-blocking Hot.Filter. If you want to do serious IR work with your Km, you can have the Hot.Filter surgically removed and replaced with clear optical glass. You can then use an IR-blocking filter in front of the lens for general photography, or any IR or other spectrum-slicing filter for specialized work. Remember than sans a Hot.Filter, the vast majority of digicam sensors are sensitive to IR and insensitive to UV.

But to answer the question: Hot.Filters usually have a sharp cutoff at 700nm.

mvecchi · 09-12-2010, 01:20 PM

Thanks for the info.

I was after the cut-off for the ir filter in front of the sensor. I'll put it at around 700nm meaning that I should be able to get decent information at around 656 nm (hydrogen alpha in astrophotography).

Cheers,
Mario

**Ex Finn.** · 09-12-2010, 01:26 PM

Not a lot of info that I have been able to find. From what I seen, the cut-off is around 700 to 750 nm.
http://www.samirkharusi.net/spectrograph
This site is astro, not specific to pentax but gives an idea.

09-09-2010, 09:20 PM	#1
mvecchi New Member Join Date: Aug 2009 Location: Brisbane Posts: 13	Km IR filter cut-off Hi all!! Does anyone know at what wavelength the IR filter in front of the sensor cuts in? Anyone have a specta for the filter? Cheers, Mario

09-10-2010, 09:00 AM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,595	There are 720nm and 900nm filters, the former being the more common, AFAIK. Edit: are you referring to the filter on the sensor itself rather than that on the lens? AFAIK, the one on the sensor cuts away all IR wavelengths. It will have to be removed if you want to do true IR photography. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

09-12-2010, 09:22 AM	#3
RioRico Veteran Member Join Date: Jun 2008 Location: Limbo, California Posts: 11,263	Various IR-pass filters are available. I use 780nm, 900nm, 930nm and 1000nm filters on my 5mpx Sony DSC-V1 'NightShot' P&S, which has a switch to flick-sway the IR-blocking Hot.Filter. If you want to do serious IR work with your Km, you can have the Hot.Filter surgically removed and replaced with clear optical glass. You can then use an IR-blocking filter in front of the lens for general photography, or any IR or other spectrum-slicing filter for specialized work. Remember than sans a Hot.Filter, the vast majority of digicam sensors are sensitive to IR and insensitive to UV. But to answer the question: Hot.Filters usually have a sharp cutoff at 700nm. Last edited by RioRico; 09-12-2010 at 09:34 AM.

09-12-2010, 01:26 PM	#5
Ex Finn. Site Supporter Join Date: Nov 2007 Location: Southern Maryland. Espoo. Kouvola. Photos: Gallery \| Albums Posts: 7,975	Not a lot of info that I have been able to find. From what I seen, the cut-off is around 700 to 750 nm. http://www.samirkharusi.net/spectrograph This site is astro, not specific to pentax but gives an idea. Last edited by Ex Finn.; 09-12-2010 at 01:32 PM.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
K7 :Cut to the chase	badbokeh	Pentax DSLR Discussion	26	06-02-2010 05:11 PM
Who cut my legs?	Urmas R.	Post Your Photos!	0	04-20-2009 02:57 AM
Does UV-filter helps to cut down the purple fringing?	alexeyga	Pentax SLR Lens Discussion	20	03-17-2009 03:37 AM
I'll cut it tomorrow,ok!	gowerray	Post Your Photos!	2	10-14-2008 05:41 AM
Who cut the cheese??	xs400	Post Your Photos!	11	06-04-2008 11:31 AM

09-12-2010, 01:20 PM	#4
mvecchi New Member Join Date: Aug 2009 Location: Brisbane Posts: 13 Original Poster	Thanks for the info. I was after the cut-off for the ir filter in front of the sensor. I'll put it at around 700nm meaning that I should be able to get decent information at around 656 nm (hydrogen alpha in astrophotography). Cheers, Mario