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Using Circular Polarizing Filters for Digital Infrared Photography



 
 
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  #1  
Old August 4th 07, 05:53 AM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
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Posts: 826
Default 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  
Old August 4th 07, 06:30 AM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Unclaimed Mysteries[_2_]
external usenet poster
 
Posts: 66
Default 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  
Old August 4th 07, 06:14 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
David Ruether
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Posts: 495
Default 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  
Old August 5th 07, 12:59 AM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
external usenet poster
 
Posts: 826
Default 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  
Old August 5th 07, 03:56 PM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
David Ruether
external usenet poster
 
Posts: 495
Default 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  
Old August 6th 07, 02:40 AM posted to alt.photography,rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
RichA
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Posts: 2,544
Default 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  
Old August 6th 07, 09:18 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Joseph Miller
external usenet poster
 
Posts: 75
Default 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  
Old August 7th 07, 12:54 AM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
external usenet poster
 
Posts: 826
Default 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  
Old August 7th 07, 07:31 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Joseph Miller
external usenet poster
 
Posts: 75
Default 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  
Old August 7th 07, 11:36 PM posted to rec.photo.digital,rec.photo.digital.slr-systems,rec.photo.digital.zlr,rec.photo.technique.nature
Wayne J. Cosshall
external usenet poster
 
Posts: 826
Default 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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