Round, threaded filters are screwed into the threads on the end of the lens. If you are using a compact digital that doesn't have threads, possibly a threaded filter adapter is available.
There are other kinds of filters such as sheets of gel or plastic. These require some sort of filter holder.
Not all cameras are suited for IR (infrared) photography. Most modern digital cameras use a strong bandpass (IR cutout filter, ICF) filter over the sensor to limit IR sensitivity. Another problem is focus since visible light and IR focus at different points and autofocus generally needs to be tweaked to focus properly.
You are often better off purchasing a dedicated IR adapted camera than to try to use a visible light camera.
The Nikon D70 has a relatively weak ICF and is a pretty good candidate for IR work using a strong IR notch filter over the lens.
Another potential problem shooting with IR is that not all lenses are suitable. Some lenses produce a strong "hot spot" on the image that is difficult or problematic to reduce, remove or compensate for.
The simplest way for most people to get started in IR photography is to use an older advanced digicam with the appropriate properties, like a Sony 707 or 717 digicam. Add an appropriate IR bandpass filter and you have a fairly flexible system to experiment in IR photography.
I use both a Minolta Dimage 7 digicam with a Hoya R72 filter, and a converted Canon XT/350D. The Minolta Dimage 7 is not optimal as it does have a hot spot, although not the worse I have seen.
I would agree that a dedicated IR digital camera is a lot more fun and convenient, but don't let that keep you from trying it out with an unconverted camera. It isn't much different than what we had to put up with in the days of IR film.
Konica IR rated ISO 12, D-76 1:1, Rolleiflex 3.5E Planar, red #25 filter
Lifepixel converted EOS 20D, 720nm filter, ISO 1600, EOS 430ex flash with DIY visible light blocking filter (double layer of unexposed but developed E6)
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There are other kinds of filters such as sheets of gel or plastic. These require some sort of filter holder.
There are also probably some DIY solutions.
Not all cameras are suited for IR (infrared) photography. Most modern digital cameras use a strong bandpass (IR cutout filter, ICF) filter over the sensor to limit IR sensitivity. Another problem is focus since visible light and IR focus at different points and autofocus generally needs to be tweaked to focus properly.
You are often better off purchasing a dedicated IR adapted camera than to try to use a visible light camera.
The Nikon D70 has a relatively weak ICF and is a pretty good candidate for IR work using a strong IR notch filter over the lens.
Another potential problem shooting with IR is that not all lenses are suitable. Some lenses produce a strong "hot spot" on the image that is difficult or problematic to reduce, remove or compensate for.
The simplest way for most people to get started in IR photography is to use an older advanced digicam with the appropriate properties, like a Sony 707 or 717 digicam. Add an appropriate IR bandpass filter and you have a fairly flexible system to experiment in IR photography.
I use both a Minolta Dimage 7 digicam with a Hoya R72 filter, and a converted Canon XT/350D. The Minolta Dimage 7 is not optimal as it does have a hot spot, although not the worse I have seen.
A couple IR samples I have done:
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Konica IR rated ISO 12, D-76 1:1, Rolleiflex 3.5E Planar, red #25 filter
Lifepixel converted EOS 20D, 720nm filter, ISO 1600, EOS 430ex flash with DIY visible light blocking filter (double layer of unexposed but developed E6)
My 300D IR converted Rebel gets way too much grain when I try to use it at its higher ISOs.
Your 20D looks like it is working pretty well.
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