Notes & Caveats
Expect to see false colour and to work the image hard in Redcine-X to develop your look, including heavy curves, inverting and transposing channels etc. Mono or Duo-tone images are often most attractive.
This filter transmits a wider range of wavelengths than any single lens is designed to accommodate at one time. Near-IR focus will be different from visible focus, potentially resulting in split or haloed focus. For best results you must filter at the front of the lens with colour or IR glass to choose the part of the spectrum you want to work in. Mixed sources of light can also show up the same focus issue.
Not all lenses perform equally in IR. Some will exhibit hotspots (if this is an issue, watch out for our upcoming IR-only filter), some will have internal reflection and flare issues, and some very modern lenses may appear darker than expected in IR due to their sophisticated coatings.
Frequently Asked Questions
For our purposes, infrared means near-IR wavelengths. Deeper than red light, and imperceptible to our vision, but still light that can be focused by typical lenses and captured by typical CMOS sensors. It is NOT representative of heat, and is distinct from thermal imaging which requires specialized lenses and sensors.
In common usage, IR light of this type is used for security cameras, for satellite and agricultural imaging, and for short range optical systems like TV remotes.
All regular OLPFS attenuate UV, IR and visible wavelengths to govern colour reproduction, making it as close as possible to a human experience of colour.
The Full Spectrum filter allows the camera sensor to see the entire range of wavelengths to which it is naturally sensitive. This means that you will have a colour image, whose colour is distorted by the presence of IR light. IR light is invisible to us, so its presence is hard to predict, but many light sources produce it. Additionally, many surfaces, especially leaves, skin, and man-made fabrics reflect a disproportionate amount of IR, creating unexpected brightness and contrast.
The IR spectrum filter removes all visible light from the image, but allows the camera to see infrared light (720nm to 950nm) which would otherwise be filtered out. The result is a monochromatic pink-hued and low-contrast image representing only this invisible light. Many objects have a very unusual appearance, blue skies become dark, skin becomes almost translucent, and direct IR light sources like LEDs become amazingly powerful and bright.
These are achieved using the Full Spectrum filter in conjunction with any number of additional solid-colour filters on the lens. Considerable post-production work is often applied to invert, swap and manipulate colour channels further.
This is most easily achieved with the IR spectrum filter, but is also possible with the Full Spectrum in conjunction with a 720nm IR pass lens filter.
The resulting image needs to be desaturated, and a heavy contrast curve applied. RED cameras are ideal for this, as the high bit-depth source allows for very aggressive grading without banding.
Most lenses allow IR to pass through, however there are many possible pitfalls. Some lenses exhibit more flare, internal reflection, and iris-shaped hotspots in the image centre.
The best performance is typically found where the lenses were designed with IR film in mind. Many decades-old stills lenses have a specific IR focus dot marked on the barrel. This is a useful indication that IR performance will be good.
If IR is being used in order to capture covert or wildlife images, where light levels are typically low, care should be taken to avoid modern cine and TV lenses, which often have IR cut coatings that can reduce sensitivity to IR by as much as four stops. For IR, old is good.
For false colour imaging, it is wise to invest in additional colour and perhaps IR pass filters, to give yourself greater creative control. Typically these are the kind of strong colour filters typically used for contrast control with black and white photography.
The main reason for soft images in IR is split focus. Due to the differing wavelengths, sharp focus is not possible for both visible light and IR light with the same focus position. In many cases cutting visible light completely, such as with the IR spectrum OLPF, yields much sharper images.
If using artificial IR sources, particularly LEDs, be aware that the LED wavelength can also cause this issue. 850nm is a good wavelength for shooting IR on RED, as it matches the peak of exposure response. However, many other IR wavelengths are available, and if mixed together in a scene, can cause soft focus.
850nm IR LED lighting is extremely efficient for this use case. It runs happily from field-portable power, and provides significantly more exposure than equivalent powered daylight LEDs with a daylight camera.
Only a dim red glow is visible to the naked eye, and almost all wildlife vision is equally insensitive to the light as human vision.
Contact KipperTie for information on rental of field-ready IR lighting kits.