Normal infrared photography would mean buying a filter (typically a Hoya R72), composing the image on a tripod, fitting the filter in front of the lens with correct filter size and taking a long exposure (~30 secs in sunlight). This still doesn’t yield a very good photo as the noise generated by the process is substantial.

I replace the filter in front of the sensor itself with one that allows radiation with wavelength greater than e.g 715nm (to ~1200nm) to pass through. This allows only (invisible to humans) infrared to pass through, resulting in images such as this:

 

 

What exactly do you do to the camera?

Digital imaging sensors in most cases are just as sensitive to infrared light as to visible light. Camera manufacturers stop infrared light from contaminating the images by placing a hot mirror filter in front of the sensor which blocks the infrared part of the spectrum while still allowing the visible light to pass.

I remove this hot mirror filter and replace it with a custom manufactured infrared or clear filter.

Autofocus is retained in both cases, and focusing through the viewfinder is still possible after the IR conversion due to the placement of the replacement mirror behind the view prism in the optical train. This makes focusing and scene adjustment easy, unlike trying to achieve this with a front lens fitted IR filter like the Hoya72.

Why is this better than using a infrared filter in front of the lens to block visible light?

The internal hot mirror filter blocks most of the infrared light from reaching the imaging sensor, thus making the exposure time much longer, usually seconds long and requiring a tripod. That long of an exposure makes it difficult to photograph and really slows you down as you have to set up a tripod for each shot.

Also because you place the opaque infrared filter in front of your lens you can't see to compose and focus, making it even more difficult and time consuming to take each shot.

After conversion the exposure times are much shorter, as an example a converted 350D on a sunny day on ISO 200 at f/8 would have a shutter speed of around 1/400th of a second. This makes handheld shots easy and since there is no filter in front of the lens you can focus and compose like normal.

What type of filters do you use?

I use Schott glass only. The filters are custom manufactured to exacting scientific specifications. Both filters are made of high quality optical glass offering excellent visible light transmission (clear glass) or infrared response (longpass infrared hot mirror).

Can I use the camera metering after infrared conversion?

The metering will work as usual. Keep in mind that the amount of infrared light varies from scene to scene even if overall brightness is the same. Since the camera light meter senses only visible light you may need to dial in some exposure compensation, example: +1.3 stops.

Do I need to manually focus to the IR mark or will the auto focus work for infrared?

Each lens diffracts infrared light differently so some lenses may be a bit off in one direction or the other and with zoom lenses the focus may be different on each zoom setting and most different at the opposite ends of the range. In most cases you can stop the lens down to f/8 or higher and get good results.

Do you make sure there is no dust trapped during the conversion? **

I get as close to a dust free conversion as is practical but in most cases there will remain a few dust specks normally invisible in photographs except at high focal length (> f10 ) and against a very light background.

These can be removed manually using a graphics editing package or with later models, using Canon's dust delete data functionality if so desired.

** Please take note.

This disclaimer is NOT unique to my service.
I can confirm similar suppliers of these services such as LifePixel and Baader,
as well as  individual outfits such as Gary Honis, Hap Griffin all have similar disclaimers in place.