I have discovered a remarkably cheap and effective IR filter

BetterSense · Aug 22, 2010

It seems you can make a dandy IR filter using nothing fancier than Lee lighting gels. I have a swatchbook of Lee lighting gells that I got for free a long time ago. I noticed that all of the gels, regardless of color, appeared crystal clear to my IR goggles. Stacking up R, G, and B yields a visually opaque filter that produces gratifying Wood effects with Efke film.

You can see the photos at http://chazmiller.com/projects/leeir.html

sun of sand · Aug 22, 2010

you could try floppy disk
i have a dichroic wratten filter

for a hobbiest digital IR kicks the pants off high priced IR films imo

but neat

MartinCrabtree · Aug 22, 2010

Not to start a 14 page discussion but isn't digital IR a simulation.

tsmyer · Aug 22, 2010

MartinCrabtree said:
Not to start a 14 page discussion but isn't digital IR a simulation.

It's not a simulation. All most all CCD and CMOS sensors have some sensitivity to IR. In fact it tends to be a problem because it causes strange color shifts. This is why the protective glass in front of the sensor is an IR blocking filter (hot mirror).

Some cameras have weaker filters than other and can be used to get the IR effect with just a regular IR low pass filter. For the people who are really serious about it, the hot mirror can be replaced with regular glass and the camera used just as a digital IR camera.

BetterSense · Aug 22, 2010

Why are we talking about digital imaging in my thread?

2F/2F · Aug 22, 2010

Good job! That certainly makes things cheaper!

removed account4 · Aug 22, 2010

thanks for posting this !

andres · Aug 22, 2010

How does it affect the image quality? I can imagine, that stacking several of these filters together might soften the image a bit. But cool anyway, now I even might try IR

patrickjames · Aug 22, 2010

I think I heard once that you can use an unexposed (black) frame of slide film as an infrared filter too. I have always just used a red 25.

The swatchbooks of lighting gels have many uses, and they are free! I have used them inside an on camera flash diffuser to balance light. I also use them for a behind the lens filter on point and shoots that won't mount a filter in front. Some of the newer wide and superwide lenses have gel filter slots in the rear as well since a filter in front tends to vignette.

2F/2F · Aug 22, 2010

Could you post a backlit digital snap of the neg, please? I want to see what you ended up with on the neg with the exposure you used.

BetterSense · Aug 22, 2010

I can't find my digital snapper right now. I really need to find it because I need to put things on ebay. When I was testing I exposed at 1s, 10s, and 30s. Both 10 and 30s exposures were grossly overexposed, but I'd say the 1s exposures came out looking pretty good. I would say the negative looks to the naked eye like a properly exposed negative, but I will probably try 2s next time. It's a bit hard to judge because the polyester base on this efke film is kind of milky.

tsmyer · Aug 22, 2010

Curious, how did you attach the gels to the lens?
I would love to give IR film a try.

fotch · Aug 22, 2010

Very very interesting. Never tried IR myself, always interested.

winger · Aug 22, 2010

An old microscopy instructor told me about these to make filters for determining the refractive index of pieces of glass relative to the liquids they were in. I only needed a certain orange one for that and the rest went into my photo DIY pile. My fisheye for 35mm takes filters in the back and I've used HIE with it with a red filter from the sample book. I did cheat when I picked it from the book and ran my regular red 25 and candidates on the microspec at work to see what wavelengths they let through.

BetterSense · Aug 22, 2010

Curious, how did you attach the gels to the lens?

I made a filter-holder sandwich out of black construction paper so that I could slip the filters in. Now that I know what filters I need to use, I made a universal IR-filter out of black foam-core, that I plan to hold in front of the taking lens during the exposure. I don't have a problem holding the filter by hand for a 1s exposure.

MartinCrabtree · Aug 22, 2010

BetterSense said:
Why are we talking about digital imaging in my thread?

Because I asked a legitimate question. Forgive me your highness as I exit your forum. Good day.

Ray Rogers · Aug 22, 2010

BetterSense said:
Why are we talking about digital imaging in my thread?

MartinCrabtree said:
Because I asked a legitimate question.

sometimes you just have to go with the flow....

Ray Rogers · Aug 22, 2010

BetterSense said:
Now that I know what filters I need to use....

Which ones did you choose as being best?

BetterSense · Aug 22, 2010

If my memory serves me, 4490 90 green, 4290 90 blue, and #26 light red. But practically anything I stacked up that was mostly opaque gave similar results. I tried as many as 6 filters, including a 2008 ND .6 to make maximum opaqueness, but it wasn't necessary.

AgX · Aug 22, 2010

BetterSense said:
I noticed that all of the gels, regardless of color, appeared crystal clear to my IR goggles.

That should not be surprising.What else would one expect from a thermoplastic hot light filter?
Surprising is to me that the net absorbance curve has a sufficient flank.

I have discovered a remarkably cheap and effective IR filter

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