The first chapter gave us an idea about the possibilities and the limits of a “black” filter that transfers only infrared light.
When using this type of filter, it is not possible to create any variation or alteration in color, other than having unified color shades – just like coloring in sepia or any other color – and we have to make do with that. There is simply no other color that is known to us that can be changed.
This example, originally in purple, shows how the shades of a monochromatic color can be slightly altered; the picture was taken by the D200 with the black 093 filter:

Model: NIKON D200 Exposure Time: 30sec F Number: 4.5 Max Aperture Value: 3.6 Focal Length: 18mm Exposure Program: Manual Exposure Bias Value: 0 ISO Speed Ratings: 200 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 27 Date Taken: 2006:01:14 10:57:23 Color Space: 65535

In the course of my review of filters, I would like to mention one more interesting filter – which is in fact orange. It transfers the orange light and downward, including the infrared. The specific model I am referring to is manufactured by B+W and is named IR 099.
One cannot reset its white balance and the picture obtained looks like this:

Model: NIKON D100 Exposure Time: 1/90sec F Number: 3.2 Max Aperture Value: 3 Focal Length: 55mm Exposure Program: Aperture priority Exposure Bias Value: 0 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 82 Date Taken: 2005:11:25 09:50:56 Color Space: 65535

By slightly editing the picture in Adobe Photoshop, and removing the excess orange – we can see its response in the red and infrared range:

Model: NIKON D100 Exposure Time: 1/90sec F Number: 3.2 Max Aperture Value: 3 Focal Length: 55mm Exposure Program: Aperture priority Exposure Bias Value: 0 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 82 Date Taken: 2005:11:25 09:50:56 Color Space: 65535

This trick does not work so well with the D200, but it somehow works well with the D2X, which is almost totally blind to infrared. The following is the filter’s direct effect:

Model: NIKON D2X Exposure Time: 1/1250sec F Number: 2.8 Max Aperture Value: 3 Focal Length: 17mm Exposure Program: Aperture priority Exposure Bias Value: 0 ISO Speed Ratings: 200 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 25 Date Taken: 2005:11:25 11:16:33 Color Space: 65535

And the result after slightly editing the picture and thinning out the orange:

Model: NIKON D2X Exposure Time: 1/1250sec F Number: 2.8 Max Aperture Value: 3 Focal Length: 17mm Exposure Program: Aperture priority Exposure Bias Value: 0 ISO Speed Ratings: 200 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 25 Date Taken: 2005:11:25 11:16:33 Color Space: 65535

One can clearly see the interesting spectral response of this filter.
The great drama occurs when using the dark red Hoya 72 filter and the B+W 092 filter, of which despite a similar spectral response, probably have response peaks in different areas of the spectrum.
One of the clear indications for this is the fact that with the Hoya filter one can easily set the white balance manually, while with the B+W filter it is possible but not easy to obtain (with the “black” filter or the 099 it is impossible).
For example, a picture taken with the D100 with the 092 filter as is:

Model: NIKON D100 Exposure Time: 1/20sec F Number: 4 Max Aperture Value: 4 Focal Length: 24mm Exposure Program: Aperture priority Exposure Bias Value: 1 Metering Mode: Center Weighted Average White Balance: Auto white balance Flash: Flash did not fire Focal Length In 35mm Film: 36 Date Taken: 2006:01:01 14:51:33 Color Space: 65535

And another picture taken the same way, and later improved with Adobe Photoshop:

Model: NIKON D100 Exposure Time: 1/160sec F Number: 4 Max Aperture Value: 4 Focal Length: 12mm Exposure Program: Aperture priority Exposure Bias Value: 0 Metering Mode: Center Weighted Average White Balance: Manual white balance Flash: Flash did not fire Focal Length In 35mm Film: 18 Date Taken: 2006:01:01 14:01:14 Color Space: 65535

What appears is a strange atmosphere, out of this world, which some people may come to like.
The D200 is significantly less sensitive to infrared, thus requiring a very long exposure time with this filter (092). As I have mentioned before, it is impossible to reset the white balance with infrared filters, probably because of the reduced sensitivity of the camera, but another trick can be used and that is to manually set the color temperature.
The adjustment range of the color temperature in the D200 is very wide: from 2,500 to 10,000 °K. the higher the temperature, the “colder” the light (tending towards blue), this is why I set it to the lowest level available, 2,500, and took a picture through the 092 filter. The picture obtained seemed washed in red but a simple autolevel with Adobe Photoshop removed quite a portion of the foreign shades:

Model: NIKON D200 Exposure Time: 2.5sec F Number: 4 Max Aperture Value: 4 Focal Length: 48mm Exposure Program: Aperture priority Exposure Bias Value: 5 ISO Speed Ratings: 400 Metering Mode: Center Weighted Average White Balance: Manual white balance Flash: Flash did not fire Focal Length In 35mm Film: 72 Date Taken: 2007:01:13 14:27:03 Color Space: 65535

The outcome is interesting, slightly reminiscent of the picture taken with this camera through the “black” filter.
But the results change completely when using the Hoya R72 filter.
This filter enables WB setting with the D100, probably due to its spectral response.
Taking a direct picture with the D100, with automatic WB, colors the entire picture with a strong red, but after resetting the camera’s WB through this filter, one obtains the following picture:

Model: NIKON D100 Exposure Time: 0.6666667sec F Number: 5 Max Aperture Value: 3.6 Focal Length: 28mm Exposure Program: Aperture priority Exposure Bias Value: 2 Metering Mode: Pattern White Balance: Manual white balance Flash: Flash did not fire Focal Length In 35mm Film: 42 Date Taken: 2007:01:12 10:25:57 Color Space: 65535

Strange blue shades are obtained, but one cannot ignore additional color information in the picture.
When transferring the picture to Adobe Photoshop, and changing the red and blue shades, one obtains an interesting result, which is peoples’ favorite and very popular among IR photographers.
The trick is to enter “Image>adjustment>channel mixer”. Enter the red channel and zero it down, and raise the blue to 100% and then do the opposite for the blue channel.
The figures aren’t precise so one can make additional improvements so as to obtain ones favorite colors. The result appears as follows:

Model: NIKON D100 Exposure Time: 0.6666667sec F Number: 5 Max Aperture Value: 3.6 Focal Length: 28mm Exposure Program: Aperture priority Exposure Bias Value: 2 Metering Mode: Pattern White Balance: Manual white balance Flash: Flash did not fire Focal Length In 35mm Film: 42 Date Taken: 2007:01:12 10:25:57 Color Space: 65535

Had the scenery included water (a pool, a pond or the sea), it would attain a nice blue shade and the picture would appear as if it were taken from a fairy tale.
After making some effort, the D100 was persuaded to reset its WB with the 092 filter and here are the results:

Model: NIKON D100 Exposure Time: 1/8sec F Number: 5.6 Max Aperture Value: 3 Focal Length: 20mm Exposure Program: Aperture priority Exposure Bias Value: 0.3333333 Metering Mode: Center Weighted Average White Balance: Manual white balance Flash: Flash did not fire Focal Length In 35mm Film: 30 Date Taken: 2007:01:20 08:36:44 Color Space: 65535

Very similar to the results obtained with the Hoya.
The Nikon cameras that are the most suitable for this affair are the D50, the D70/S and the D100. I have not checked the D40 yet, so I cannot establish its performance.
In conclusion, by using various infrared filters one can obtain interesting results, especially if the field of vision includes vegetation that reflects infrared and water reservoirs that absorb it.
The filter that is the most suitable for obtaining interesting results, is the Hoya 092. The price of these filters strongly depends on their diameter. Up to a diameter of 67mm, the prices are reasonable – several tens of dollars, but the prices of the wider filters, the 72mm and the 77mm, rise up to hundreds of dollars.
These filters reveal an interesting and strange world and they let us produce fascinating pictures of the world that is beyond our visible range!