Instructional video from photographer Tim Shoebridge on how to prepare your SIGMA sd Quattro camera for Infrared Photography. 
Photographer Tim Shoebridge shares his insight on how shooting with the sd Quattro nurtures his personal creativity and touches upon infrared photography as one avenue of creativity – a feature that the sd Quattro and sd Quattro H uniquely offers amongst mirrorless cameras in the September 18, 2017 blog post found on the following link:
https://www.sigmauk.com/extend-your-creativity-with-the-sigma-sd-quattro-by-tim-shoebridge/ 
Below is an exert from the article along witht a link to the instructional video:
“Infrared radiation is invisible to our eyes but it is all around us. It is generated mostly by the sun, but also by certain artificial lights and by heat sources. Unlike our eyes, every digital camera sensor is highly sensitive to infrared radiation, but this radiation is interpreted by the sensor mainly in the red channel and so will cause very unnatural looking images unless it is filtered out. Camera sensor manufacturers achieve this by permanently fixing in place a special infrared blocking filter directly on top of the sensor to prevent infrared radiation from entering. This filter is commonly called a “hot mirror” due to its reflective surface and the fact that it helps prevent heat build-up”.
Sigma and Foveon have decided not to follow the approach of a permanently fixed hot mirror. Instead they have designed a removable IR blocking filter that is right at the mouth of the lens mount on both the sd Quattro and sd Quattro H. With a little practice you will find it very straight forward to remove and re-fit this IR blocking filter. I have put together a very brief video to show you how I do it here: