# Anyone used a Hoya R72 infrared filter?



## peanut170 (May 17, 2012)

Love the look of infrared photos, but I just can't seem to get mine looking like videos I watch and other pics I see. Anyone tried this and have any pointers?


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## bratkinson (May 18, 2012)

First, a disclaimer...I have NO experience in infra-red photography. However...I've read and heard enough to know a little about it. Ie, a little knowledge can be a dangerous thing!

To do infra-red photography, you either need infra-red film in a film camera, or a specially modified digital sensor to 'sense'/receive infra-red wave length light. A digital camera is, for the most part, maybe 100%(?) insensitive (eg, colorblind) to infra-red. On the other end of the light spectrum, digital sensors are also insensitive to ultraviolet (UV), as well. That's why UV filters on digital cameras are nothing more than decorations, at best, and an image killer/lens killer, at worst. 

In short, putting an IR filter on your digital camera will have no effect whatsoever other than some degree of image quality loss.

As far as modifying (replacing?) the sensor to be infra-red sensitive, one of my friends had it done to an old 5 MP Nikon he had and played with it for a while before selling it due to lack of interest.


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## usayit (May 18, 2012)

bratkinson said:


> specially modified digital sensor to 'sense'/receive infra-red wave length light. A digital camera is, for the most part, maybe 100%(?) insensitive (eg, colorblind) to infra-red. On the other end of the light spectrum, digital sensors are also insensitive to ultraviolet (UV), as well. That's why UV filters on digital cameras are nothing more than decorations, at best, and an image killer/lens killer, at worst.
> 
> In short, putting an IR filter on your digital camera will have no effect whatsoever other than some degree of image quality loss.
> 
> As far as modifying (replacing?) the sensor to be infra-red sensitive, one of my friends had it done to an old 5 MP Nikon he had and played with it for a while before selling it due to lack of interest.



NOT accurate.  The following was taken with an unmodified camera.







More info here:

http://www.thephotoforum.com/forum/landscape-cityscape/249802-edit-abandoned-farmhouse-infrared.html


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## usayit (May 18, 2012)

Yes.. you can have a DSLR modified:

1) Replace the IR cut filter on sensor with a clear optical glass - PRO: allows dual use camera, CON; requires the filter in front of lens, for DSLRs you will need to prefocus
2) Replace the IR cut filter on sensor with a IR filter - PRO: Allows the use and focus of a DSLR as normal (no filter in front of lens).   Con: Camera will be IR only.

Yes.. you can take IR shots with a non-modfied DSLR.  My images were all taken on a non-modified camera.  But because of the combination of the IR filter on lens, IR cut filter on sensor and the sensitivity of the sensor itself, you will most likely not be able to get handhold able exposures.  More than likely you should be expecting long exposures even in bright light.   IMPORTANT: This is highly dependent on the camera's sensitivity to IR.  Mine is abnormally sensitive to IR (some say design fault) so the shots were for the most part handheld exposures in bright daylight.

Google will bring up some people's experiences with IR photography and what type of camera they used.  There is also this forum:  http://irphotocom.proboards.com/index.cgi

All images will require post-processing....  as you can see in the thread what the image looks like out of camera.   My other camera which is essentially the same camera but the IR issue was corrected.  It is not at all sensitive to IR... to the point that it is practically useless to getting a good IR image to work with.


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## TCampbell (May 18, 2012)

You can check the website of Gary Honis -- he's an astrophotographer, but he has detailed instructions on how to modify some models of digital cameras to shoot IR.  WARNING:  If your camera has a warranty, these procedures will surely void it.  Not for the feint of heart.  If you cannot afford to risk ruining your camera, don't do this.

In any case, filters tend not to be "perfect".  You can spend obscene amounts of money to get filters that are very close to perfect.  For less obscene amounts of money filters merely tend to block "most" of what they're designed to block... but not all of it.

You can now buy a version of the Canon 60D which they call the "60Da" -- it's a special astrophotography version of the 60D.  The IR/UV filter in front of the sensor is replaced with a different IR/UV that allows significantly more IR to pass.  They include a drop-in filter accessory which you insert behind the lens (the camera has a holder built-in which doesn't exist on the regular 60D) so that it should block roughly the equivalent of a standard 60D.  This allows you to drop in the filter and use it as a normal DSLR, or remove the filter and allow the IR to pass so you can use it as an IR camera or astrophotography camera.

The only downside of the 60Da is the price.  The regular 60D is usually about $900.  The 60Da is $1500.  So basically you pay a $1500 premium for the fact that you're getting an IR DSLR that doesn't force you to void your warranty to modify the camera. 

In fairness... I've got a guy in my astronomy club who owns this camera.  I was looking at photos of a galaxy taken with the 60Da which look pretty amazing.  I put my 5D II (stock -- not modified for IR) onto the very telescope the the 60Da used and shot a galaxy, but my camera didn't come even remotely close to gathering as much light or rendering the detail.  Clearly allowing the IR makes a significant difference.  I'm "sold" on the idea... although I haven't bought the camera yet.


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## bratkinson (May 18, 2012)

usayit...

I'm rather puzzled here.  I was under the impression that an IR filter and UV filter both did the same thing, just at opposite ends of the visible light spectrum - remove the indicated wave lengths from the image.  Does the Hoya R72 IR filter actually -convert- infra-red colors to something in the visible spectrum?  Or does it -remove- all the reds (visible and IR) from the image?  In short, what does it do?


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## coastalconn (May 18, 2012)

I just so happen to have a full spectrum converted Nikon D200, the cut filter was replaced with clear glass so I can record crazy strange colors or straight IR.  Some people say the disadvantage of full spectrum is that it blocks the viewfinder which is true, my easy workaround is to focus and compose the shot, lock focus and exposure with the shutter button and simply hold the IR cut filter over the lens.  With a conversion, you can still have your normal shutter speed.  With a normal camera, the IR block filter is very strong.  To do IR, you need a tripod and a long exposure time to allow the IR light to penetrate the block filter.  Exposure times of 10 secs or more are not uncommon.  You will have to shoot in manual mode for the long exposure time and also you will need a pretty small F-stop.  Even with my camera, after I adjusted the AF mirror, I still need to shoot upwards of f11-f16 to get sharp photos.  

I have a flickr set showing the results of various filters on the full spectrum camera.   Nikon d200 full spectrum/infrared - a set on Flickr 

To usayit, the one step that it looks like you didn't try yet was swapping the red and blue channels(split rgb, combine bgr), to give the deep blue sky look... 
I hope you don't mind a did a quick attempt on it


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## coastalconn (May 18, 2012)

Visible light is roughly 400-700nm (nanometers)  UV light is under 400nm and not visible to the human eye.  UV filters just block any leakage below that frequency.  IR filters actually block all visible light (or most depending on the filter) below 720nm.  The hot mirror filter on digital sensors are basically designed to block light below 400 and light above 700.



bratkinson said:


> usayit...
> 
> I'm rather puzzled here.  I was under the impression that an IR filter and UV filter both did the same thing, just at opposite ends of the visible light spectrum - remove the indicated wave lengths from the image.  Does the Hoya R72 IR filter actually -convert- infra-red colors to something in the visible spectrum?  Or does it -remove- all the reds (visible and IR) from the image?  In short, what does it do?


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## coastalconn (May 19, 2012)

Understanding a 720nm filter.  Same filter, same card, same f-stop, same lighting.  The top picture is my normal D90, the 720nm is black and you can not see through it.  The Bottom picture is the full spectrum D200, It "sees" right through the filter with ease...


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## bratkinson (May 19, 2012)

CoastalConn - Thank you for the explanation and pictures!  And as they say, a picture IS worth 1000 words!  

In your description, you indicated there already is a UV and IR blocking filter in every 'normal' digital camera.  I always thought that the design of the light receptors themselves precluded 'reading' UV and IR.  Apparently not so.  It is the built-in filter you had replaced with plain glass in your D2000, right?  So now the D2000 sees 'everything', visible and invisible to the naked eye?  I can see where trying to use that setup on a outside on a summer day "as is" would result in very blown out pictures due to the IR from heated up surfaces!  So placing the 720nm (IR) filter in front of the lens then blocks the visible light and lets only the UV through, right? 

One last question...

In the pictures with the filter on the card...can you see through it with your eyes?  In any light?  Just curious.


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## usayit (May 19, 2012)

coastalconn said:


> To usayit, the one step that it looks like you didn't try yet was swapping the red and blue channels(split rgb, combine bgr), to give the deep blue sky look...
> I hope you don't mind a did a quick attempt on it



I don't mind at all....  After that old thread was posted, I did experiment with swapping the channels.


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## usayit (May 19, 2012)

bratkinson said:


> It is the built-in filter you had replaced with plain glass in your D2000, right?



That's what he did.. Usually not "plain" glass but clear glass that is of optical quality.   It allows the sensor underneath record the full spectrum of what it is capable of detecting.  The other type of conversion is to replace the filter on the sensor with an actual filter of choice. 

I think the confusion is the terminology.   There are actually two types of "IR filters" that are being referred to in this thread.  One is a IR blocking (or cut) filter.  This filter blocks or prevents infrared wavelengths from penetrating ( allows visible light spectrum ).  Most off-the-shelf DSLRs have this type of filter built-in because both CCD and CMOS sensors are sensitive to the infrared spectrum and the intent is to prevent IR from "leaking" onto the picture which produce odd color shifts on certain materials/surfaces.  The other filter is an IR filter (in bratkinson's case, a 720nm) filter which is the opposite.  It blocks wavelengths 720nm and below; including visible light but allows wavelengths 720nm and above including IR to penetrate.  

See the following graph:






If you look at the top end of the visible spectrum, you will see that humans detect up to 700nm.  The IR filter of 720nm type will block anything below including the visible spectrum.   UV as you can see in the chart is on the complete other end of the visible spectrum with a different set of filters that act at those wavelengths.


In bright daylight, I can see a tiny bit through my IR filter (very little).  Mine is not as "aggressive" as bratkinson's 720nm.  It was designed to filter out wavelengths 650mm and below.  So a human can still see wavelengths from 650nm -> 700nm.  Gives a slightly different effect and allows for some additional exposure since my camera is still un-modified.  With a 720nm filter, it should be pitch black (maybe not totally since no filter is perfect).


http://www.lifepixel.com/

They do conversions and have a good amount of info on their website.


PS> An old military application to IR photography was for reconnaissance.  Notice that foliage tends to reflect off a lot of IR and buildings (targets) don't.


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## coastalconn (May 19, 2012)

The 720nm filter I have is pure black and you can see no light through it, unless you look directly at the sun(I don't recommend this, btw).  When people talk about cleaning a sensor, they are technically cleaning the hot mirror filter and "AA" filter. The sensor is always underneath a filter.  

 Don't get yourself confused by saying "heated" up surfaces.  IR is light not heat.  That would be a thermal imaging camera.  But bright sunlight is reflected as "white" light and the cameras sensor is not designed to meter infrared light.  Therefore I often have to use negative exposure compensation, often -2 to -3 to stop the images from being washed out and flooded with light.  Also be aware that IR has a higher frequency and therefore has a different focus than normal light.  This is easily compensated for if you have "live view".  




bratkinson said:


> CoastalConn - Thank you for the explanation and pictures!  And as they say, a picture IS worth 1000 words!
> 
> In your description, you indicated there already is a UV and IR blocking filter in every 'normal' digital camera.  I always thought that the design of the light receptors themselves precluded 'reading' UV and IR.  Apparently not so.  It is the built-in filter you had replaced with plain glass in your D2000, right?  So now the D2000 sees 'everything', visible and invisible to the naked eye?  I can see where trying to use that setup on a outside on a summer day "as is" would result in very blown out pictures due to the IR from heated up surfaces!  So placing the 720nm (IR) filter in front of the lens then blocks the visible light and lets only the UV through, right?
> 
> ...


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## dxqcanada (May 19, 2012)

I used Infrared filters with film ... though back in the days of Kodak HIE a deep red would suffice. 
Right now I am going to be working with an R72 with Efke IR820 ... still waiting for the foliage to fully come out.

Some info: Digitaltruth Photo


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## bratkinson (May 19, 2012)

Interesting stuff!  Before this, I never knew there were filters to cut out visible light and leave the IR range, or, as Usayit said, with a 650, most of the visible spectrum is gone.  I was somewhere lost between thermal imaging thinking it was reading IR, and thinking that an IR capable camera was 'fixed' to only sense IR.  

There's a whole lot to learn here, and quite obviously, a whole 'field' of photography in IR that I never really looked at.  

Many thanks for the highly informative responses!  I've learned a lot!  I'm sure the OP, peanut170, also found a wealth of information here, as well.


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## KmH (May 20, 2012)

A few physics classes always help.


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