A normal RGB IQ4 back has an IR-UV cut filter in front of the sensor so you're not able to see NIR.
BR
Yair
Yair you may have missed my reply above to which he was responding.
A standard camera (P1 or otherwise) strongly filters IR (at least, all of them after the Leica M8 residual-infrared-sensitivity disaster).
However, that just sets the bar for how strongly you must filter visible to shoot IR.
For example, simplifying things a bit to rough stops: if a given camera natively filters 7 stops of IR and you use enough lens filtration to filter 14 stops of visible then you'll be shooting infrared images.
Now it's extremely important to note that 1) you'll be stacking filters and that can degrade sharpness and 2) you'll be filtering an extreme amount of the total light so your shutter speed will lengthen by rather extreme amounts.
For example with "sunny 16" rule of thumb a bright mid-day photo would be roughly 1/100th of a second at f/16 at ISO100. So in the example above with 14 stops of light loss due to stacking IR-pass (on lens) with IR-block (on sensor) filters your new exposure is 160 seconds long. On the one hand that's patently absurd. On the other hand some people use ultra-strong ND filters to shoot long exposures during the day, and enjoy the temporal blurring that is a bit ethereal/unworldly/unusual. And if you open to f/2.8 and up to ISO3200 you'll be at ~1/15 which is vaguely hand-holdable with a wide lens and a very generous definition of "sharp enough".
Is any of this what I would do if I was deeply interested in infrared imaging? Absolutely not! Given the money I'd buy an IQ4 Achromatic without an IR filter, as several of our clients have bought from us. Given a lower budget I'd buy whatever camera I could justify and send it to max-max for IR filter removal.
But it can be done. And it can be an interesting foyer into infrared photography for someone playing around or those who like weird gear combinations. I'd put this roughly in the world of making a pinhole camera using your digital back, or doing direct shadowgrams onto your sensor, or mounting an old IMAX Cinema Projector lens to your IQ back - which is a lot of fun even if it's not what I'd call "deeply serious" or "technically appropriate".
