Infrared for dumbies question

[peter_koch]

<p>I know very little about infrared, while looking online about a project of mine which is making homemade filters for TLRs, I ran across articles about making infrared filters for your digital camera etc. My question is would regular slides, provia, astia, velvia, etc show anything if I used a infrared filter, or is it only infrared film?</p>

<p>Peter Koch<br>

www.photographybypeterjkoch.com</p>

[franklin_polk]

<p>Most films drop off significantly into the infrared; you'll essentially get nothing. The only color IR film available to consumers (I'm assuming you'd like some since your brought up color slide film) was Ektachrome infrared (EIR). It was discontinued a few years back; new it was about $25 roll, I don't follow how much it goes for on ebay, but IIRC, it is around $55 a roll. If you really, really want some, it is still made...in 9" wide, 1000" foot rolls for aerial purposes, its original design intent. It appears that the closest to IR is Velvia 100, which extends to about 690nm. Infrared generally is considered to start at 700nm, usually more. That is why infrared films are infrared films, their sensitivites extented far past 700nm, IIRC, HIE went to about 925nm. </p>

[Mike Gammill]

<p>Most films (both black & white and color) are only senstive out to about 650nm. A few get to 700nm. Above 700nm (give or take a little) is considered near-infrared territory. A few extended red sensitive films may reach 720 to 750nm, but filtering all but IR makes for very long exposures. A true IR film (at least in the near IR where IR can be focused by a lens) starts around 750nm and extends somewhat beyond 1000nm. Kodak's discontinued HIE infrared was good to about 950nm. Most current IR films stop at 820nm which will give some prettty strong IR effects with the proper filter. So what happens if you use a filter that passes IR with very little visible light with a film that doesn't have IR sensitivity? (A)you could get nothing (B)if the exposure is long enough you may get an image from the small amount of visible light that gets through the filter ©you may get some limited IR effects (unlikely) if the film's sensitivity extends closer to IR that the specs indicate. I'm attaching a 5 minute time exposure during a sunny day on Panatomic-X through a TIffen R72 filter.<br>

Notice the red stop sign looks very pale as would with a dark red filter and the trees are dark for a similar reason. But the grass is a bit lighter. Some leaves show blur due to long exposure.<br>

Even if I were to subject this scan to extensive image processing I don't think it would ever have an IR look to it.</p><div></div>

[JDMvW]

<p>Let me trot out this very informative, if a little dated, site on doing infrared, yet again (<a href="http://folk.uio.no/gisle/photo/ir.html">link</a> ). Although it is about digital, the information on filters, lenses, etc. is still valid.</p>

[randall ellis]

<p>Take a look at the spec sheet for any given black and white film and it will show the range of sensitivity in wavelengths of light of that film. Match that with the filter you wish to use, which also has a range of light wavelengths passed, and as long as the film has sensitivity in the range that the filter passes you will get something. The problem is trying to find the amount of exposure required for a film/filter combination. The more wavelength passed by the filter that the film is sensitive to, the shorter the exposure will need to be and vice versa. If all you have is a small range of wavelength passed that the film is sensitive to, you'll end up needing a long exposure to register any image.</p>

<p>- Randy</p>

[robert hall]

<p>Keep in mind as well of reciprocity failure. As your exposures become longer than 1 second (for most films) you will have to deal with reciprocity.</p>

<p>As for making IR filters, they need to be unexposed but developed slide film. Any slide film will work. Depending on the dye packets one will get a texture with the film used. I have used 4x5 film and I usually try one or 2 sheets for effect.</p>

<p>Best of luck</p>

<p>-Robert Hall</p>