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Back to the IR light source concept...



 
 
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  #11  
Old August 1st 04, 07:35 AM
columbotrek
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Default Back to the IR light source concept...

I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut
out what you need. Look for a low pass gell at about 750nm. A cheep way
is to process a sheet of unexposed slide film if you need a large piece.
Or take some of the ends from a processed roll of 35mm or 120 slide
film. You can layer them if you need it darker to visable light.
Performance wise though, it is going to be hard to beat a real IR
illuminator like what is use on night vision devices. Oh by the way,
all CCD sensors are sensitive to IR (down to 1300nm) light. All you
need to do is to remove the camera's high pass filter and replace it
with a clear to IR glass. I have been playing around with a CCD digital
camera with a Hoya R72 (720nm low pass) It is an Olympus 2020 and I am
comparing it to Kodak HIE film with the same filter. The film is about
5 stops faster than the digital sensor.

Don Bruder wrote:

Some of you may recall my post a few weeks ago asking about IR LEDs,
filters, and other yakkety-yak about cheap ways to fab a light source
that puts out either pure IR, or "close enough to it", with little or no
visible component, for use in what boils down to a homebrew "Night
Vision" system designed around a video camera that has a
well-demonstrated sensitivity to IR in the same region of the spectrum
that TV remotes use.

  #12  
Old August 1st 04, 07:35 AM
columbotrek
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Posts: n/a
Default Back to the IR light source concept...

I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut
out what you need. Look for a low pass gell at about 750nm. A cheep way
is to process a sheet of unexposed slide film if you need a large piece.
Or take some of the ends from a processed roll of 35mm or 120 slide
film. You can layer them if you need it darker to visable light.
Performance wise though, it is going to be hard to beat a real IR
illuminator like what is use on night vision devices. Oh by the way,
all CCD sensors are sensitive to IR (down to 1300nm) light. All you
need to do is to remove the camera's high pass filter and replace it
with a clear to IR glass. I have been playing around with a CCD digital
camera with a Hoya R72 (720nm low pass) It is an Olympus 2020 and I am
comparing it to Kodak HIE film with the same filter. The film is about
5 stops faster than the digital sensor.

Don Bruder wrote:

Some of you may recall my post a few weeks ago asking about IR LEDs,
filters, and other yakkety-yak about cheap ways to fab a light source
that puts out either pure IR, or "close enough to it", with little or no
visible component, for use in what boils down to a homebrew "Night
Vision" system designed around a video camera that has a
well-demonstrated sensitivity to IR in the same region of the spectrum
that TV remotes use.

  #13  
Old August 1st 04, 09:53 AM
Don Bruder
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Default Back to the IR light source concept...

In article Sa0Pc.8484$Xn.5197@fed1read05, columbotrek
wrote:

I have never found any economy in building what I can buy. Just takes
to much time. You can buy inexpensive IR gells from which you can cut


HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")


Performance wise though, it is going to be hard to beat a real IR
illuminator like what is use on night vision devices.


Performance is secondary to price. A "real" illuminator with any kind of
range is, like buying the IR-pass filter, way outside my budget, even
with the idea of going for the cheapest available.

Oh by the way,
all CCD sensors are sensitive to IR (down to 1300nm) light.


Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.
  #14  
Old August 2nd 04, 11:46 PM
croweflight
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Default Back to the IR light source concept...



Don Bruder wrote:
HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")

Is unexposed but developed scrap slide film beyond your budget? Perhaps
you just need something to keep occupied with. Like polishing old CDs.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

The CCD sensors are before they place a high pass filter in front of it
which is why I suggested to remove the thing and replace it with clear
glass to preserve the focus. Which is just what Sony does for their
night mode. The lever moves the high pass filter out of the way. But
now they also strap the aperture wide open when you place it in night
mode. So if you use it in the daylight with an IR low pass filter the
sensor saturates.
  #15  
Old August 2nd 04, 11:46 PM
croweflight
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Posts: n/a
Default Back to the IR light source concept...



Don Bruder wrote:
HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")

Is unexposed but developed scrap slide film beyond your budget? Perhaps
you just need something to keep occupied with. Like polishing old CDs.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

The CCD sensors are before they place a high pass filter in front of it
which is why I suggested to remove the thing and replace it with clear
glass to preserve the focus. Which is just what Sony does for their
night mode. The lever moves the high pass filter out of the way. But
now they also strap the aperture wide open when you place it in night
mode. So if you use it in the daylight with an IR low pass filter the
sensor saturates.
  #16  
Old August 3rd 04, 06:00 PM
Don Bruder
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Posts: n/a
Default Back to the IR light source concept...

In article sKFPc.5111$Oi.15@fed1read04,
croweflight wrote:

Don Bruder wrote:
HAH! Cheapest IR-pass filters I was able to find, whether gell, plastic,
or glass, are *WAY* beyond my budget for this sort of tinkering. Besides
- Doing it myself is (A) Entertaining (B) Educational and (C) a fun
challenge. (Hmm... maybe C should read "both of the above?")

Is unexposed but developed scrap slide film beyond your budget? Perhaps
you just need something to keep occupied with. Like polishing old CDs.


Ahh, I get it... post a response so you can make a snide remark. FTR,
it's my time to do with as I please, so you can take your snotty
commentary and shove it where the sun don't shine.

Replace "all" with "most", and I'll buy into that last statement. Some
of them are very IR sensitive. Others barely notice IR at all, while
still others are effectively totally blind to it. Depends on the maker
and the process they used. External pre-filtering obviously effects the
accuracy of that statement...

The CCD sensors are before they place a high pass filter in front of it
which is why I suggested to remove the thing and replace it with clear
glass to preserve the focus. Which is just what Sony does for their
night mode. The lever moves the high pass filter out of the way. But
now they also strap the aperture wide open when you place it in night
mode. So if you use it in the daylight with an IR low pass filter the
sensor saturates.


Wasn't that little addition (cranking the aperture wide open in "night"
mode) in response to the "Oh my god! If it's used that way in daylight,
it's able to take nude pictures of clothed people!!! Oh, the horror! It
MUST BE STOPPED!" garbage that started flowing when somebody actually
tried it?

I guess saturating the sensor would do a good job of stopping such
things... A picture/footage isn't worth much if it's just a white-out.

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.
  #17  
Old August 7th 04, 02:14 AM
Sir Charles W. Shults III
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Posts: n/a
Default Back to the IR light source concept...

Just as a note- if you are removing aluminum based reflective coatings
(virtually all of them!), then never never scrub them off with abrasives.
Dip them in ammonia and it will dissolve the aluminum right away, leaving
the plastic pristine and perfect.

Cheers!

Sir Charles W. Shults III, K. B. B.
Xenotech Research
321-206-1840


  #18  
Old August 7th 04, 10:56 AM
Don Bruder
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Posts: n/a
Default Back to the IR light source concept...

In article ,
"Sir Charles W. Shults III" wrote:

Just as a note- if you are removing aluminum based reflective coatings
(virtually all of them!), then never never scrub them off with abrasives.
Dip them in ammonia and it will dissolve the aluminum right away, leaving
the plastic pristine and perfect.


Excellent idea. But what about "breaking the glaze" of the coating over
top of the aluminum? Doesn't seem to me like ammonia will be very
effective on aluminum it can't get in contact with...

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
Short form: I'm trashing EVERY E-mail that doesn't contain a password in the
subject unless it comes from a "whitelisted" (pre-approved by me) address.
See http://www.sonic.net/~dakidd/main/contact.html for full details.
  #19  
Old August 9th 04, 04:07 PM
Chris Hodges
external usenet poster
 
Posts: n/a
Default Back to the IR light source concept...

Don Bruder wrote in message ...
snip
After spending some time looking for, and a grand total of 8 dollars
acquiring, a few of these "black" CDs, I went to work on taking my idea
from the realm of theory to reality. And I'm pleased to say "it works!"

snip

So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".


Have you tried (in other words it probably won't work, but you never
know) aplying a water based clear varnish to the ground side. If the
refractive index is similar enough to the plastic (tinted
polycarbonate I would guess - normal polycarbonate has n~1.56) and you
can get good coverage right into the grooves (you might need to dilute
with water) AND you get an even layer it might be good enough - it's
light delivery, not imaging that you're after. Underdriving the bulb
will increase the amount of IR at the expense of vis as previously
mentioned, so perhaps the bulb from a 4 or 6 cell maglite would help
as well.

Chris

(p.s. google has given me 1.37-1.48 for refractive index of varnishes)
  #20  
Old August 9th 04, 04:07 PM
Chris Hodges
external usenet poster
 
Posts: n/a
Default Back to the IR light source concept...

Don Bruder wrote in message ...
snip
After spending some time looking for, and a grand total of 8 dollars
acquiring, a few of these "black" CDs, I went to work on taking my idea
from the realm of theory to reality. And I'm pleased to say "it works!"

snip

So at this point, I'm trying to figure out the best way to polish out
the scratches left by the steel wool, and get back to a truly
transparent (rather than translucent) finish on my homemade "filter".


Have you tried (in other words it probably won't work, but you never
know) aplying a water based clear varnish to the ground side. If the
refractive index is similar enough to the plastic (tinted
polycarbonate I would guess - normal polycarbonate has n~1.56) and you
can get good coverage right into the grooves (you might need to dilute
with water) AND you get an even layer it might be good enough - it's
light delivery, not imaging that you're after. Underdriving the bulb
will increase the amount of IR at the expense of vis as previously
mentioned, so perhaps the bulb from a 4 or 6 cell maglite would help
as well.

Chris

(p.s. google has given me 1.37-1.48 for refractive index of varnishes)
 




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