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Writer / Elizabeth Holmes

The infrared process

A Guide for Using Infrared Film.

Always be careful when handling chemicals. Read the health and safety instructions.

I have been using black and white infrared film for the past ten years and it has become my choice of film for fine art photography.

With infrared film, you are seeing in a new light that creates luminous highlights and enhances texture, contrast, and depth.

The results can be very exciting but working with this film requires understanding a few basic concepts that I would like to briefly cover:

All 3 images use Kodak HIE, 35mm film
35mm Film #25 Filter	Bright Sunlight #25 Filter	Bright Sunlight Overcast Sk

What Is Infrared?

Light can be characterized as the full range of wavelengths on the electromagnetic spectrum. The human eye is sensitive to only a small portion of visible colors on the spectrum starting with blue at 400nm (nanometers) extending to red at 700nm. Wavelengths shorter than the visible light range are ultraviolet radiation and longer wavelengths are infrared radiation.

Infrared film is sensitive to visible light, ultraviolet radiation, and infrared radiation. An infrared photograph records infrared radiation reflected off the subject from a light source. The light source can be the sun, our natural light source, or artificial light like tungsten or flash. The effects of infrared are evident in leaves, grass, and foliage that contain greater levels of infrared. They appear lighter, recording from white to light gray in a photograph, while the sky and water actually absorb infrared and appear darker in some photographs.

All 3 images use Kodak HIE, 35mm film
Sepia Toned, Bright Sunlight	Handcolored Bright Sunlight	Handcolored, Shade

Film Types and Sensitivity

There are several types of infrared film available on the market, each having varying levels of sensitivity to ultraviolet light, visible light, and infrared radiation. These levels of sensitivity will determine how a photograph will look.

Konica 120mm, #25 Filter Bright Sunlight, Handcolored	Kodak HIE 35mm, #25 Filter Bright Sunlight, Handcolored	SFX 200 35mm, #25 Filter Tungsten Light, Hancolored

Kodak Infrared HIE

Kodak High Speed Infrared HIE is a moderately high contrast film and the most sensitive to infrared radiation with a range of 250nm (ultraviolet) to 900nm (infrared). It is the only infrared film lacking an anti-halation backing in its emulsion, allowing light to bounce back through the negative. This explains the halo effect around bright objects and why this film has more sensitivity to light than other infrareds. Kodak sells HIE film in 35mm film-36 exposure rolls.

Image above: Kodak HIE 35mm, after storm-halos of light reflect off grass and sand.

Konica 750

Konica 750 film is a fine grain infrared film with sensitivity to violet and blue from 400-500nm and sensitivity to infrared between 640-820nm, peaking at 750nm. Without filtration, Konica 750 is similar to panchromatic film, which records the full range of visible light. In the 120 format, this film produces fine grain photographs with excellent sharpness and tonality. Konica 750 is sold in 35mm film-24 exposure and 120-12 exposure rolls.

Ilford SFX

Ilford SFX 200 has consistent sensitivity from ultraviolet to red and reaches out to 740nm in the infrared range, peaking at 720nm. SFX 200 is a medium speed film with moderate contrast and full panchromatic sensitivity without a filter. SFX 200 film is sold in 35mm film-36 exposures and 120 rolls-12 exposures.

Loading Film

Kodak infrared film is very sensitive to light and must be loaded and unloaded in total darkness. I always use a black changing bag to load and unload my film. Kodak recommends
storing unprocessed film at 55°F in a cool dry place, so I store my film in the refrigerator and generally, allow an hour before loading into the camera. After shooting a role, process your film as soon as possible. Konica and SFX are less sensitive to light but should be loaded and unloaded in subdued light.

Filters

The purpose of a filter is to block some wavelengths from reaching your film and to let other wavelengths through. In general, I use a #25 red filter on my camera lens because I really enjoy looking through this filter and I prefer the amount of infrared that is transmitted. There is a variety of filters for infrared film and depending on your films particular sensitivity range, some filters will work better with your film.

• #8 Yellow filter - begins transmitting light at 450nm, blocking ultraviolet and most blue light.
• #15 Orange filter - begins transmitting at 500nm, blocking all ultraviolet and blue light.
• #25 Red filter - begins transmitting at 600nm, blocking ultraviolet, blue, green and yellow.

Opaque Filers transmit only infrared light:

• #89B filter begins transmitting at 720nm
• #88A filter at 750nm
• #87 filter at 800nm
• #87C filter at 850nm

Kodak HIE, with the highest infrared sensitivity, can be used with an opaque filter #87C. Konica 750 extends to 820nm and will not expose beyond the #87 filter. SFX 200 infrared is
sensitive to 740nm and will not expose beyond the #89B filter.

Exposures and ISO Ratings

When using a filter you must adjust your exposure. Manufacturers provide filter factors for adjusting f-stops. If a filter factor is doubled, your exposure needs to be increased by one stop. For example, a filter factor of two requires a one-stop increase and a filter factor of four requires a two-stop increase. If I use a camera with TTL metering, I make a through the lens exposure reading with the filter on the lens and I find the exposures to be accurate. If I meter without my #25 red filter on the camera, I make a two-stop exposure adjustment. I suggest bracketing +/- a half stop until you become familiar with what your film can do.

Kodak HIE: Kodak does not provide an ISO rating but I rate my film between ISO 100 and ISO 200. At ISO 100, the negative has less contrast and I prefer to print with this type of negative if I am going to handcolor a photograph.

Konica 750: Konica recommends rating their film at ISO 32 without a filter, and shooting f5.6 at 1/60 using a red filter in sunny, outdoor conditions. I have rated Konica at ISO 25 and ISO 50 and have gotten good results when shooting in bright sunlight.

Ilford SFX 200: SFX can be rated between ISO 200 to 800 and because of the lower sensitivity to infrared does not require an infrared focus correction.

Focusing

Most lenses have an infrared focus mark which acts as a guide for focusing. Filters and film should be considered when adjusting the focus. If you use a #25 red filter, you record a larger range of infrared wavelengths, so shift your lens closer to the infrared focus mark after focusing and not as close when using a yellow or orange filter.

Image left: Hyperfocal point meeting the infrared focus mark on wide angle lens using HIE.

My choice of film is usually Kodak HIE because it has the largest infrared range, so I move my lens closer to the infrared focus mark after focusing and not as close with SFX 200 or Konica 750 film. For landscape photography, with HIE film and a wide-angle 28mm lens, I set my hyperfocal point to meet the infrared focus mark to ensure sharp focusing.

Developing

When I rate Kodak HIE film at ISO 100, I have it developed with D76 at 68°F for 9 minutes. Each film manufacturer provides development recommendations but if you are developing the film yourself, the key is to be consistent during the development process to learn about your negatives.

Conclusion

Using infrared film gives you the opportunity to work outside the boundaries of conventional film to create photographs with emotion, drama, and mystery. It has enabled me to be more creative in my work and has been an important element in creating my style. I have found the results of using infrared film are well worth the time spent understanding and learning about it.