OldNotMold Loc: Just North of

In a previous post that probably contained too many questions, my bad, one of the responders (on topic of filter selection) mentioned that there was no need for an IR filter for haze reduction or presumably any other reason. The responder said that the camera already does this. I'm not sure if he/she meant that modern camera lenses filter IR radiation as a function of their construction (glass, coatings) or if there is some magic in the camera(s) that does this. I'd like to know if IR filters are available and useful for in-camera haze reduction or other effects or not. Your thoughts please. You have provided great advice in the past, and I'm sure you will again. Thanks.

krl48 Loc: NY, PA now SC

You mention haze reduction. Are you perhaps thinking of UV (ultra violet) filters, which were often used in film photography for haze reduction?

OldNotMold Loc: Just North of

I'm familiar with UV filters. I was specifically wondering about IR filters. I believe that they can also be useful for creating some special B+W effects.

OldNotMold Loc: Just North of

I did a little research and found that the IR filter will produce some interesting B+W-like images since it doesn't transmit visible radiation. Perhaps the other person's comment about haze reduction was true but for a different mechanism that a UV filter. I think that I have my answer. Thanks.

OldNotMold Loc: Just North of

... than a UV filter.

f8lee Loc: New Mexico

An IR filter is not required for haze reduction because, for one thing, haze is the result of higher frequency light waves (thus more towards UV).

Digital cameras have an IR filter (of sorts) built into them because the imaging chip in its native state is particularly sensitive to IR wavelengths of light - thus the manufacturer has an IR cutoff filter layered over the CCD or CMOS chip to enable human-visible light to get through more cleanly. When you send your DSLR in to "convert" it to an IR camera, they service removes this filter thus enabling the chip to "see" those frequencies.

An IR filter that screws onto the front of your lens (like an UV or CP filter does) is one that only allows IR wavelengths through (thus it appearing pretty much black to our eyes - since we do not see those wavelengths). Using one of these on a non-converted DSLR will approximate the effect of making the (permanent) conversion described above, though of course it will require longer exposures since the IR cutoff filter on the chip will be removing much of the IR light passing through the filter on the lens.

In any case, IR photography (film as well) is "black and white" because IR light is outside the band of wavelengths we can see - from the shorter wavelengths that are deep purple to the longest bands that are red - IR are even longer wavelengths that fall outside of the entire RGB rainbow concept altogether. There was a technique in film days of generating "false color" in IR shots, pretty much by assigning different visible colors to different wavelengths in the IR band, but of course those colors have nothing to do with what we normally perceive.

IR shots of nature scenes show the leaves of trees (that we see s green) as being bright or all white since those leaves reflect most of the IR wavelength light that falls on them.

OldNotMold Loc: Just North of

Kodak had a problem at one time in the old color negative film days where one of their emulsion sensitizing dyes (the one that was red light sensitive for use in the cyan layer) didn't cut off sharply enough and so was too IR sensitive. It really messed up things, took them a short while to realize why images were seeing more "red" than the eye was seeing.

I understand what you are saying. The new info was the filtration coating on the sensor... thank you for that especially. It all makes sense to me now. I too was having a problem with the "haze" statement someone else had mentioned in another thread. Perhaps they were referring to the fact that the resulting BW image appears to be less hazy. So you've cleared up that one as well... thanks again.

pecohen Loc: Central Maine

If you look around you will find there are businesses that will modify any of a variety of cameras to operate as IR cameras and on occasion they will also convert these cameras to be full-range cameras. I have to assume that the first option is accomplished by trading the filter that is internal to the camera for the purpose of blocking IR and replacing it with a filter that blocks visible light. The second option would only remove the filter that blocks IR.

IR is generated by heat an our eyes are not sensitive to IR. I have to assume that digital cameras typically block IR since letting it get to the sensor would create some effects that we would interpret as odd. Birds can often see IR so perhaps they would find such images less odd.

If you simply put a filter on your conventional digital camera you will likely not see much at all unless through a long exposure.

nicksr1125 Loc: Mesa, AZ

If you don't want to have your camera modified, Cokin makes an IR filter (#87) as does Hoya. An easier option would be to use a dark red filter & a polarizer.

mborn Loc: Massachusetts

if you want to try IR photography the easiest way is to buy a filter. You have to focus without the filter on the lens then add the filter and add longer time to the exposure
Read this blog for info http://wbhunt.com/blog/travel-photography-infrared-photography/

lamiaceae Loc: San Luis Obispo County, CA

I think somehow you got slightly confused and seem to have gotten straightened out more or less. f8lee gave a really good answer and explanation. I'd like to add to that a bit. There was a one time Kodak Infrared Ektachrome film that produced false color slides from IR. You pretty much just used the camera and lens as is. In fact I may recall that I had to use a 2A or 2B (stronger UV) filter because the film had extended sensitivity to both longer and shorter wave length light. So you get IR + Visible on your slides (the UV would fog it). Now for Kodak High Speed Infrared B&W Film, you put a IR passing filter over your lens.

For digital as noted, you can have a camera converted to full time IR use by having the low and hi pass filters removed have a camera that can with the use of the proper filters over the lens have an IR & UV & Visible camera. But the filters are tricky to use and incredibly expensive. Also with this set up you can't see through the lens with the filters on, everything looks black. I believe there is a fancier way of doing this by replacing the on sensor filters with one that only blocks visible light yet passes IR & UV. I've seen incredibly images on line of that. Some with both in the same shot.

And on the cheap, like f8lee said, you can just place a IR only passing filter on your lens after focusing, but the exposures are really long. I've done IR by several methods. Both film and digital. I have a few glass and gel IR filters, 850, 880, 900 nm. My converted camera has a 667 nm cut off so I get color plus IR. Makes for some interesting images but I now wish I had gone for a 850/880 nm so I could get B&W IR that looks like B&W film IR.

This is my first attempt at IR with my converted camera. It is not my best and the file is rather small, cropped for a specal use, but it is what I could grab quickly for this post.

(Download)

dickwilber Loc: Indiana (currently)

Light of differing wave lengths (i.e., differing colors) focuses at differing points, as you should be aware, from the lens nodal point. Lens manufacturers have spent much time and effort to get around this fact, but our lenses are actually compromises to get the best balance. Infrared light focuses even further away from that compromise than the visible wave lengths. Consequentially, lenses (prime lenses - zooms don't work because the correction is focal length dependent) used to have a red auxiliary mark (in red, sometimes labeled "R") near the principle focus mark.

To focus for IR photography, you first focused normally, then found the point on the distance scale opposite the principle focus mark, then rotated the focus ring until the IR focus mark was opposite that same point on the distance scale. On my ancient Zuiko (Olympus) lenses, the IR mark is to the right of the normal focus mark, meaning that you adjust the focus a little closer for IR. Of my six prime lenses, three have the separate IR focus mark; a 24 mm's IR focus mark falls just at the right f/5.6 depth of field mark; the 50 mm lens at the right f/4 DOF mark; and the 200 mm just outside the right f/16 DOF mark. I do not know how much the correction might be influenced by the specific lens design.

IR photography can be rewarding, but be aware the focus anomaly!

dickwilber Loc: Indiana (currently)

I followed up on my previous response to mborn by googling IR DSLR camera conversions and their comments on focus. It was enlightening.

LifePixel indicated that “...each lens design and focal length, even each focal length within a zoom lens will focus IR light differently.”, but that they calibrate your camera (when they do the conversion – depending on which conversion) to compensate for this focus aberration, but, “... even after calibration of your camera to your zoom lens the telephoto end could still have a focus shift. There are some exceptions though, the following lenses work really well in infrared through the entire zoom range: Nikkor AF-S 18-70 DX and AF-S VR 18-200DX lenses as well as the Canon EF-S 15-85mm f/3.5-5.6 IS.”

The Luminous Landscape reviewed the conversions by MaxMax where the camera-lens combination was also calibrated, but went on to say: “So, at the end of the day, it appears that cameras converted by MaxMax do indeed focus properly in the Infrared, without user intervention. But, my own tests show that at the extremes, either with very long focal lengths or very wide apertures, an extra stop of two of stopping down doesn't hurt to provide a depth of field safety margin.”

So it appears that the photographic world has indeed progressed from my film age knowledge of the subject, and depending on which camera you had converted, by whom, when, and which option you chose, you may escape the focus anomalies I noted – or not.

alggomas Loc: Wales, United Kingdom.

Why not get a camera you have converted to IR photography?
I mean are you continually going to shoot IR.

You can get IR filters for cameras but they vary in intensity.

I would suggest, but check out other responders, that converting anj unused camera is the way to go.

dickwilber Loc: Indiana (currently)

I am thinking about it. I have three cameras mentioned in one of the articles I referenced that are currently unused, so that part is easy. I've never done IR in any form and it might be fun. I can't see getting too deeply involved in IR, however, so conversion cost is definitely a factor.