Clearing the air about IR photography

Adiemus · 26th January 2005

Did some reading on IR and here's my summary...

First of all we must know what is light
Light is usually referred to as the portion of the electromagnetic spectrum that the human eye can detect. This light is visible. Beyond this range lies the ultraviolet spectrum and the infrared radiation.

This form of energy which is emitted by the sun is differentiated by their specific wavelengths. Visible light ranges from 380 - 730nm. This range is further divided into specific colours, like a rainbow.

Wavelengths that are shorter than those in the visible spectrum (ie. 1 - 380nm) are ultraviolet radiation. Longer wavelengths, (ie. 730 - 1000000nm ) make up infrared radiation.

The infrared spectrum is divided into two regions: near and far infrared. Near infrared, from 730 - 2000nm, is invisible to the eye but can be photographed. Far infrared, from 1200 - 1000000nm, is perceived as heat.

So what is infrared photography?
Infrared photography records the reflected infrared radiation off the subject from a light source. When you include the sun or another light source in your shot, you are actually photographing actual infrared radiation. Most of the time, what we do is reflective infrared photography.

Light or Heat
Infrared films are not sensitive to the far infrared range, therefore they are not sensitive to heat. If they were, they would fog up when your body heat comes into contact with it.

What a lot of people in CS get mixed up with is this; that IR photography is capturing the heat radiated off an object or person. This is not true. When you see Predator or some show with thermal detection, that's actually electronic thermography. This is the technology that is used in night vision scopes and surveillance recordings. This calls for devices that are sensitive to the far infrared range. Temperature differences in the object are displayed as colour differences on a video monitor. It is sometimes loosely termed as infrared photography, but it is actually infrared thermography.

teerex · 26th January 2005

Originally Posted by Adiemus

Did some reading on IR and here's my summary...

First of all we must know what is light
Light is usually referred to as the portion of the electromagnetic spectrum that the human eye can detect. This light is visible. Beyond this range lies the ultraviolet spectrum and the infrared radiation.

This form of energy which is emitted by the sun is differentiated by their specific wavelengths. Visible light ranges from 380 - 730nm. This range is further divided into specific colours, like a rainbow.

Wavelengths that are shorter than those in the visible spectrum (ie. 1 - 380nm) are ultraviolet radiation. Longer wavelengths, (ie. 730 - 1000000nm ) make up infrared radiation.

The infrared spectrum is divided into two regions: near and far infrared. Near infrared, from 730 - 2000nm, is invisible to the eye but can be photographed. Far infrared, from 1200 - 1000000nm, is perceived as heat.

So what is infrared photography?
Infrared photography records the reflected infrared radiation off the subject from a light source. When you include the sun or another light source in your shot, you are actually photographing actual infrared radiation. Most of the time, what we do is reflective infrared photography.

Light or Heat
Infrared films are not sensitive to the far infrared range, therefore they are not sensitive to heat. If they were, they would fog up when your body heat comes into contact with it.

What a lot of people in CS get mixed up with is this; that IR photography is capturing the heat radiated off an object of person. This is not true. When you see Predator or some show with thermal detection, that's actually electronic thermography. This is the technology that is used in night vision scopes and surveillance recordings. This calls for devices that are sensitive to the far infrared range. Temperature differences in the object are displayed as colour differences on a video monitor. It is sometimes loosely termed as infrared photography, but it is actually infrared thermography.

Thanks for the interesting read Adiemus

ungku · 27th January 2005

nice write up!

vortex · 27th January 2005

Originally Posted by ungku

nice write up!

so when you joining us ungku?

ark19 · 27th January 2005

Thanks Adiemus,
Here's something to add on:
http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c1
http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html

geek65536 · 27th January 2005

Great job, though I think you might want to mention that infrared photography will NOT let you see in the dark. That is done with an infrared flashlight. Since we can't see it, but things that are sensetive to infrared can, it is used by the military in stealth operatoins, or by security cameras, so it can see them, but they can't see it.

The infrared spectrup is a lot like the color spectrum in the way it works. To some degree, I think everybody does give off a very very tiny bit of color light too, though most is reflected. It is pretty much the same in infrared. Infrared photography is really just... "seeing things in a different light."

vortex · 27th January 2005

another thing i have to say out too....

this infrared (IR) we are taking....is not the "see through clothes" type!!!

so dont worry if we point our cameras at u...or think we are trying to be funny by taking "infrared" pics

pianodancer · 28th January 2005

Originally Posted by vortex

another thing i have to say out too....

this infrared (IR) we are taking....is not the "see through clothes" type!!!

so dont worry if we point our cameras at u...or think we are trying to be funny by taking "infrared" pics

Although this IR we are discussing here is not about the 'see through clothes' type, the concept is the same. Some materials are invisible in the eyes of infrared, which is why we can capture the 'infrared radiation' that is bouncing off beneath the material.

I may be opening a can of worms here, but we should educate readers instead of treating this 'see through' issue as taboo. It's really simple on how to protect oneself from being capturing 'what lies beneath'.
http://forums.clubsnap.org/showthrea...5&page=4&pp=20

vortex · 28th January 2005

Originally Posted by pianodancer

Although this IR we are discussing here is not about the 'see through clothes' type, the concept is the same. Some materials are invisible in the eyes of infrared, which is why we can capture the 'infrared radiation' that is bouncing off beneath the material.

I may be opening a can of worms here, but we should educate readers instead of treating this 'see through' issue as taboo. It's really simple on how to protect oneself from being capturing 'what lies beneath'.
http://forums.clubsnap.org/showthrea...5&page=4&pp=20

Good point there about educating readers

though im not too sure how, since im not technically inclined in photography

Pablo · 28th January 2005

Originally Posted by vortex

Good point there about educating readers

though im not too sure how, since im not technically inclined in photography

Hi,
When talking to anyone here at work regarding IR shooting, I refer to it as "Daylight Infrared Photography".

Show a photo and it is then obvious.

If anybody still thinks that it can be also be used for peep photography;
they probably have trouble with most things in life

26th January 2005	#1
Adiemus Member Join Date: May 2004 Location: Small island.... Posts: 1,562	Clearing the air about IR photography Did some reading on IR and here's my summary... First of all we must know what is light Light is usually referred to as the portion of the electromagnetic spectrum that the human eye can detect. This light is visible. Beyond this range lies the ultraviolet spectrum and the infrared radiation. This form of energy which is emitted by the sun is differentiated by their specific wavelengths. Visible light ranges from 380 - 730nm. This range is further divided into specific colours, like a rainbow. Wavelengths that are shorter than those in the visible spectrum (ie. 1 - 380nm) are ultraviolet radiation. Longer wavelengths, (ie. 730 - 1000000nm ) make up infrared radiation. The infrared spectrum is divided into two regions: near and far infrared. Near infrared, from 730 - 2000nm, is invisible to the eye but can be photographed. Far infrared, from 1200 - 1000000nm, is perceived as heat. So what is infrared photography? Infrared photography records the reflected infrared radiation off the subject from a light source. When you include the sun or another light source in your shot, you are actually photographing actual infrared radiation. Most of the time, what we do is reflective infrared photography. Light or Heat Infrared films are not sensitive to the far infrared range, therefore they are not sensitive to heat. If they were, they would fog up when your body heat comes into contact with it. What a lot of people in CS get mixed up with is this; that IR photography is capturing the heat radiated off an object or person. This is not true. When you see Predator or some show with thermal detection, that's actually electronic thermography. This is the technology that is used in night vision scopes and surveillance recordings. This calls for devices that are sensitive to the far infrared range. Temperature differences in the object are displayed as colour differences on a video monitor. It is sometimes loosely termed as infrared photography, but it is actually infrared thermography. Last edited by Adiemus; 27th January 2005 at 12:28 AM.

27th January 2005	#7
vortex Senior Member Join Date: Sep 2004 Location: SG / LDN Posts: 3,021	another thing i have to say out too.... this infrared (IR) we are taking....is not the "see through clothes" type!!! so dont worry if we point our cameras at u...or think we are trying to be funny by taking "infrared" pics __________________ My Photos on Flickr IR Photography

27th January 2005	#3
ungku Member Join Date: Jan 2005 Location: East Posts: 164	nice write up!

27th January 2005	#5
ark19 Senior Member Join Date: Jan 2002 Location: ark19.multiply.com Posts: 3,080	Thanks Adiemus, Here's something to add on: http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c1 http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html

27th January 2005	#6
geek65536 New Member Join Date: Dec 2004 Posts: 11	Great job, though I think you might want to mention that infrared photography will NOT let you see in the dark. That is done with an infrared flashlight. Since we can't see it, but things that are sensetive to infrared can, it is used by the military in stealth operatoins, or by security cameras, so it can see them, but they can't see it. The infrared spectrup is a lot like the color spectrum in the way it works. To some degree, I think everybody does give off a very very tiny bit of color light too, though most is reflected. It is pretty much the same in infrared. Infrared photography is really just... "seeing things in a different light."