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05-25-2012, 08:59 AM   #1
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K10d infrared filter??

I'm starting to do some research into IR photography. I was thinking of buying an IR filter prior to going full throttle and having a camera modified. Does anyone know how well the built in IR filter works in the K10d? I understand that the *istD has a weak IR filter and works well with lens filters. Is that the case with the K10d?

05-25-2012, 09:26 AM   #2
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K10D has a strong filter, you need exposures for 1 minute or longer.
It can be done though, i've done it and some more here.
05-25-2012, 10:05 AM   #3
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Are many strengths of IR-pass filter, most commonly 680-720-780-900-950-1000nm. The higher the number, the less visible light intrudes. Using a 680nm or 720nm filter on an unmodified camera allows enough visible light to frame and focus a shot, albeit with fairly long exposures. Stronger filters require either a modified camera or a LOT of light. I used a 950nm filter on my unmodified K20D to shoot the recent annular eclipse. But I normally use filters stronger than 720nm only on a Sony 'Nightshot' P&S, whose IR-blocking hot.filter flips away for IR shooting.

For camera modifications, I strongly recommend having the internal hot.filter replaced with clear optical glass rather than with a fixed-wavelength IR-pass filter. Such a mod allows both IR shooting (with an IR-pass filter on the lens) and 'normal' photography (with an IR-blocking filter on the lens). Otherwise, the camera can be used for IR only.
05-25-2012, 10:35 AM   #4
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Broad band camera

QuoteOriginally posted by RioRico Quote
.......

For camera modifications, I strongly recommend having the internal hot.filter replaced with clear optical glass rather than with a fixed-wavelength IR-pass filter. Such a mod allows both IR shooting (with an IR-pass filter on the lens) and 'normal' photography (with an IR-blocking filter on the lens). Otherwise, the camera can be used for IR only.
If the internal hot mirror is replaced with clear glass or fused silica, the camera can see into the near UV as well as into the near IR.

External filters can then be used to select the wavelength regions of interest from UV through visible to IR.

Dave

05-25-2012, 10:44 AM   #5
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QuoteOriginally posted by RioRico Quote
Are many strengths of IR-pass filter, most commonly 680-720-780-900-950-1000nm.
isn't that the range?
05-25-2012, 11:30 AM   #6
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I'm thinking about trying this filter on the kit lens as a starting point. I mostly shoot landscape shots so I am not to concerned about long exposures. I figure if I like the IR that much I can pick up a *istD or similar camera and have it modded. For $20 I figure it's worth a try!
05-25-2012, 12:09 PM   #7
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QuoteOriginally posted by newarts Quote
If the internal hot mirror is replaced with clear glass or fused silica, the camera can see into the near UV as well as into the near IR.

External filters can then be used to select the wavelength regions of interest from UV through visible to IR.
Yes, unlimited spectrum-slicing! The Fuji forensic dSLRs were built so appropriate internal filters were easily swapped. I nearly bought one instead of my K20D -- but I would have been limited to Nikon-mount glass.

QuoteOriginally posted by Anvh Quote
isn't that the range?
Yes, and each point in that range gives different results. On my Sony Dsc-V1 'Nightshot' I use 780-900-930-1000nm filters. On my unmodified K20D I use 720-780-950nm filters. I've a Minolta F300 modded with an internal 720nm filter. All different tools for different tasks. That 950nm filter on 900mm of optics on my K20D was just what I needed for the recent annular eclipse.

QuoteOriginally posted by mr tibbs Quote
I'm thinking about trying this filter on the kit lens as a starting point. I mostly shoot landscape shots so I am not to concerned about long exposures. I figure if I like the IR that much I can pick up a *istD or similar camera and have it modded. For $20 I figure it's worth a try!
Such a 720nm filter is quite popular just because it *does* pass enough visible light for use on an unmodified camera. It's a good place to start. Have fun!

Something to keep in mind: Shooting IR lowers image resolution on Bayer-filter sensors. The microfilters are RGBG, with two Green pixels and one Blue pixel for every Red pixel. Those GBG pixels see nothing of reduced IR; only the R pixel sees the most photons. So a 16mpx camera in visible light effectively outputs 4mpx rougher images in IR. I'm not sure how Foveon sensors work here, although it may be significant that Sigma (producer of Foveon gear) made forensic dSLRs. Other sensors lacking Bayer filters may be well-suited for IR work. Yeah, that Leica Monochrome, ooh ooh...

Last edited by RioRico; 05-25-2012 at 02:29 PM.
05-25-2012, 01:27 PM - 1 Like   #8
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QuoteOriginally posted by RioRico Quote
Something to keep in mind: Shooting IR lowers image resolution on Bayer-filter sensors. The microfilters are RGBG, with two Green pixels and one Blue pixel for every Red pixel. Those GBG pixels see nothing of IR; only the R pixel sees photons. So a 16mpx camera in visible light effectively outputs 4mpx images in IR. I'm not sure how Foveon sensors work here, although it may be significant that Sigma (producer of Foveon gear) made forensic dSLRs.
Green & Blue Bayer filters are typically opaque in the very near IR but do a good job transmitting from ~ 800-1000 nm. This enables one to do multicolored IR work.


Separating the RGB channels, using appropriate weighting factors, and mathematically adding and subtracting color channels allows some separation of IR bands. Red minus G+B is a band from 700 to about 780nm, Green-Blue ~750 - 800nm, B ~ 780 - 1100+nm

Here's an image taken with a 720nm filter, no PP, showing real IR coloring effects (the blue color of the sunglasses corresponds to long IR wavelengths.)


Dave in Iowa

05-25-2012, 02:30 PM   #9
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Thanks for clearing that up, Dave! I (hopefully) corrected my post.
05-25-2012, 04:11 PM   #10
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Lots of good info here!! Now I just have to learn the terminology!
05-25-2012, 04:30 PM   #11
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QuoteOriginally posted by mr tibbs Quote
Lots of good info here!! Now I just have to learn the terminology!
And that leads to one of my mini-rants: Much of photography involves learning the jargon. Think of these forums as an extended language seminar. We learn the craft by (besides practicing) absorbing how to describe our tools and actions. Pretty soon, we internalize the concepts: DOF, AOV, IR-block, focal vs focus range, fast vs slow, FF vs MF, AF vs MF, stops, etc. Gibberish becomes communication. Hopefully.
05-25-2012, 05:07 PM   #12
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QuoteOriginally posted by RioRico Quote
Much of photography involves learning the jargon. Think of these forums as an extended language seminar.
I agree 100%. When I bought my first DLSR (K100D) I actually took a local community class to learn the language. Without that class I would still be lost and using my DSLR as a point and shoot!
05-25-2012, 05:25 PM   #13
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INtersting might try a 720 filter =]
05-25-2012, 05:27 PM   #14
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QuoteOriginally posted by RioRico Quote
And that leads to one of my mini-rants: Much of photography involves learning the jargon. Think of these forums as an extended language seminar. We learn the craft by (besides practicing) absorbing how to describe our tools and actions. Pretty soon, we internalize the concepts: DOF, AOV, IR-block, focal vs focus range, fast vs slow, FF vs MF, AF vs MF, stops, etc. Gibberish becomes communication. Hopefully.
Sometimes i help another photographer with the lighting and several times we are asked what language we speak XD
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