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Using Circular Polarizing Filters for Digital Infrared Photography
Hi All,
I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Cheers, Wayne -- Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ |
#2
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Using Circular Polarizing Filters for Digital Infrared Photography
Wayne J. Cosshall wrote:
Hi All, I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Can Digital HDRIR be far behind? Ever tried using a pair of crossed linear polarizers? As you approach 90 degrees, the spectrum of light that makes it through apparently gets weighted toward the red and IR. Not an appealing prospect to add these to a filter stack, and the pair didn't substitute well for the IR pass filter, but I was amused anyway. Observed with unmodded Sony F828 in "nightshot" mode. Crossed linear polarizers stacked with IR pass filter, in an attempt to reduce the need for additional ND filters. (Yeah I know, I should just go get the thing modded) Imagine my surprise when I saw the IR target scene not fade at all as I approached 90 degrees. Several filters have unexpected effects when used outside their intended spectra. A Hoya X1 *green* filter is more effective at attenuating IR than yer basic 2 or 3 stop ND filter. YMMV. HTH. HAND. C. -- It Came From Corry Lee Smith's Unclaimed Mysteries. http://www.unclaimedmysteries.net In a time of deception telling the truth is a revolutionary act. - George Orwell |
#3
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Using Circular Polarizing Filters for Digital Infrared Photography
"Wayne J. Cosshall" wrote in message u... I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Wayne Interesting results. When I use my old Sony TRV9 (FS, BTW, in very nice low-use condition...) Mini-DV camcorder (mine is daylight IR enabled) with an IR filter, I also generally add a circular polarizer, which gives a little more control over the image, as you found. Some samples shot from a car are at www.donferrario.com/ruether/ir.htm -- David Ruether http://www.donferrario.com/ruether (see our "restaurant menu", at www.donferrario.com/ruether/menu.htm) |
#4
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Using Circular Polarizing Filters for Digital Infrared Photography
Good shots. I have a TRV9, I have to look into getting it converted or
modified. Cheers, Wayne Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ David Ruether wrote: "Wayne J. Cosshall" wrote in message u... I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Wayne Interesting results. When I use my old Sony TRV9 (FS, BTW, in very nice low-use condition...) Mini-DV camcorder (mine is daylight IR enabled) with an IR filter, I also generally add a circular polarizer, which gives a little more control over the image, as you found. Some samples shot from a car are at www.donferrario.com/ruether/ir.htm |
#5
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Using Circular Polarizing Filters for Digital Infrared Photography
"Wayne J. Cosshall" wrote in message u... David Ruether wrote: "Wayne J. Cosshall" wrote in message u... I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Wayne Interesting results. When I use my old Sony TRV9 (FS, BTW, in very nice low-use condition...) Mini-DV camcorder (mine is daylight IR enabled) with an IR filter, I also generally add a circular polarizer, which gives a little more control over the image, as you found. Some samples shot from a car are at www.donferrario.com/ruether/ir.htm --David Ruether Good shots. I have a TRV9, I have to look into getting it converted or modified. Wayne Any of the Sony 1-CCD camcorders can be modified to prevent the IR switch from also forcing the camera to widest aperture and too slow a shutter speed for daylight IR video (first installed in late TRV9s due to Sony's silly prudery and the myth of "x-ray" vision for the camera - but fortunately, mine is an earlier version, and not hobbled by this nonsense). One day I tried it outdoors, and it worked fairly well, so I added a red filter, and it worked better yet. A polarizer improved the results further, and finally replacing the red with an IR filter worked very well. I use the camera in B&W mode to lose the "tooth paste green" look...;-) BTW, I prefer IR in motion to stills (it is just plain more fun - and somehow less "hokey" looking...). -- David Ruether http://www.donferrario.com/ruether |
#6
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Using Circular Polarizing Filters for Digital Infrared Photography
On Aug 4, 1:30 am, Unclaimed Mysteries
theletter_k_andthenumeral_4_...@unclaimedmysterie s.net wrote: Wayne J. Cosshall wrote: Hi All, I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Can Digital HDRIR be far behind? Ever tried using a pair of crossed linear polarizers? As you approach 90 degrees, the spectrum of light that makes it through apparently gets weighted toward the red and IR. Not an appealing prospect to add these to a filter stack, and the pair didn't substitute well for the IR pass filter, but I was amused anyway. Observed with unmodded Sony F828 in "nightshot" mode. Crossed linear polarizers stacked with IR pass filter, in an attempt to reduce the need for additional ND filters. (Yeah I know, I should just go get the thing modded) Imagine my surprise when I saw the IR target scene not fade at all as I approached 90 degrees. Several filters have unexpected effects when used outside their intended spectra. A Hoya X1 *green* filter is more effective at attenuating IR than yer basic 2 or 3 stop ND filter. Why use any of that junk when you can buy interference filters that have almost dead-stop cutoffs at any wavelength you'd like? You can get cutoff filters, narrow band filters or even notch filters, all with steep attenuation and throughput. YMMV. HTH. HAND. C. -- It Came From Corry Lee Smith's Unclaimed Mysteries.http://www.unclaimedmysteries.net In a time of deception telling the truth is a revolutionary act. - George Orwell |
#7
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Using Circular Polarizing Filters for Digital Infrared Photography
Wayne J. Cosshall wrote:
"Wayne J. Cosshall" wrote in message u... I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Wayne A few remarks, FWTW. There are two different influences affecting the final results in your IR pictures. A circular polarizer consists of two filters: a linear polarizer followed by a quarter-wave retarder. Neither of these is fully achromatic, that is, they only have a limited wavelength range over which they are fully effective. Outside its range the linear polarizer will have decreasing effect in polarizing light, and outside its range the retarder will convert less of the lineraly polarized light to circular. Both tend to start failing rather badly as you go into the IR, so I would expect diminished affect by rotating the filter in the IR. How much depends on the specific polarizer and could change with maker. For my research I had achromatic polarizers and retarders fabricated that worked from the UV to the IR, but they were very expensive. Normal ones made for cameras start losing there effectiveness in the blue and the red, only working well in between. Joe |
#8
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Using Circular Polarizing Filters for Digital Infrared Photography
Hi Joe,
Thanks for that input. Makes perfect sense and With my Hoya filters I was seeing more effect visually than the camera was. Where do you go to get these custom filters made? Cheers, Wayne Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ Joseph Miller wrote: Wayne J. Cosshall wrote: "Wayne J. Cosshall" wrote in message u... I've been experimenting with using a circular polarizing filter when shooting digital infrared images: http://www.dimagemaker.com/article.php?articleID=1053 Wayne A few remarks, FWTW. There are two different influences affecting the final results in your IR pictures. A circular polarizer consists of two filters: a linear polarizer followed by a quarter-wave retarder. Neither of these is fully achromatic, that is, they only have a limited wavelength range over which they are fully effective. Outside its range the linear polarizer will have decreasing effect in polarizing light, and outside its range the retarder will convert less of the lineraly polarized light to circular. Both tend to start failing rather badly as you go into the IR, so I would expect diminished affect by rotating the filter in the IR. How much depends on the specific polarizer and could change with maker. For my research I had achromatic polarizers and retarders fabricated that worked from the UV to the IR, but they were very expensive. Normal ones made for cameras start losing there effectiveness in the blue and the red, only working well in between. Joe |
#9
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Using Circular Polarizing Filters for Digital Infrared Photography
Wayne J. Cosshall wrote:
Hi Joe, Thanks for that input. Makes perfect sense and With my Hoya filters I was seeing more effect visually than the camera was. Where do you go to get these custom filters made? Cheers, Wayne Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ The custom filters would not work with normal cameras. They are quite bulky, fragile, and can require careful alignment. I'm an astronomer and use them on very big telescopes (e.g., the Keck Telescopes) to measure polarization of faint astronomical objects. Joe |
#10
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Using Circular Polarizing Filters for Digital Infrared Photography
Ah, so you are a professional photographer. You should have said. I
almost went into astrophysics but went into computer science instead. Cheers, Wayne Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ Joseph Miller wrote: Wayne J. Cosshall wrote: Hi Joe, Thanks for that input. Makes perfect sense and With my Hoya filters I was seeing more effect visually than the camera was. Where do you go to get these custom filters made? Cheers, Wayne Wayne J. Cosshall Publisher, The Digital ImageMaker, http://www.dimagemaker.com/ Blog http://www.digitalimagemakerworld.com/ Publisher, Experimental Digital Photography http://www.experimentaldigitalphotography.com Personal art site http://www.cosshall.com/ The custom filters would not work with normal cameras. They are quite bulky, fragile, and can require careful alignment. I'm an astronomer and use them on very big telescopes (e.g., the Keck Telescopes) to measure polarization of faint astronomical objects. Joe |
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