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The Clip Filter System

Owners of Canon EOS cameras have another interesting option [for digital infrared work]. Once the camera's internal IR blocking filter has been swapped for a clear glass filter, the Clip Filter System manufactured by Astronomik is an alternative to lens mounted filters.

This system was originally devised for astrophotography; however, some of the filters offered by Astronomik can also be used in infrared photography. There are several advantages. First, only one filter is necessary for all EOS compatible EF lenses regardless of lens diameter. Secondly, during long exposures, the clip filter also protects the camera's sensor from dust. The Clip Filter System is presently compatible with EOS types 300D, 350D, 400D, 10D, 20D, and 30D. No further modifications are necessary; the filters snap right into the camera body, without the need for tools.

In addition to filters used in astronomy, two infrared filters are available at the time of this book's publication: 742 nm (ProPlanet 742) and 807 nm (ProPlanet 807). The disadvantage of this system is that the viewfinder darkens completely when the filter is inserted. This makes it difficult to arrange and set up the shot, which in most cases would have to be done before inserting the filter.

The only way to circumvent this problem is by using an attachable, external viewfinder as described in the chapter about equipment. Astronomik is developing an infrared (IR) blocking filter with the same properties as Canon’s normal internal IR blocker. This will solve another problem by making it possible to quickly and cheaply restore the camera's visible light capabilities. Also in development are filters for other camera makes. You can find more information at www.astronomik.com.

OPTIMIZED INFRARED CAMERAS

Compact Cameras (with internal infrared blocker)

The internal blocking filter is permanently swapped for a fixed internal infrared filter. No additional filter is necessary on the main lens.

Advantages:
• High shutter speed
• No hot spot
• Adapter tube and threaded ring on main lens unnecessary

Disadvantages:
• Normal light pictures impossible

Compact Cameras (with clear glass filter)

The internal blocking filter is permanently swapped for a clear glass filter. An additional infrared filter is necessary on the main lens.

Advantages:
• High shutter speed
• The camera's ability to shoot in visible light is preserved if an infrared blocker is attached to the main lens
• A variety of infrared filters can be used

Disadvantages:
• Either an adapter tube or filter threading on the main lens is necessary
• Depending on the focal length, a hot spot can become visible in images

SLR Cameras (with internal infrared blocker)

The internal blocking filter is permanently swapped for a fixed internal infrared filter. No additional filter is necessary on the main lens.

Advantages:
• High shutter speed
• All lenses can be used without producing hot spots
• Focusing and setting up the shot can be done through the viewfinder

Disadvantages:
• Normal light pictures impossible

SLR Cameras (with clear glass filter)

The internal blocking filter is permanently swapped for a clear glass filter. An additional infrared filter is necessary on the main lens.

Advantages:
• High shutter speed
• The camera's ability to shoot in visible light is preserved if an infrared blocker is attached to the main lens
• A variety of infrared filters for different wave lengths can be used

Disadvantages:
• The viewfinder blackens when an infrared filter is attached
• Depending on the lens, hot spots may occur

Links to the first and third installments in our completed series are below:

www.imaginginfo.com/web/online/Online-Exclusives/Digital-Infrared-Photography-Explored--Part-I/49$4258

www.imaginginfo.com/web/online/Online-Exclusives/Digital-Infrared-Photography-Explored--Part-III-/49$4317

Excerpted from the new book release Digital Infrared Photography by Cyrill Harnischmacher and published by Rocky Nook. For more information visit http://www.rockynook.com.