On Mon, 18 Nov 2019 22:33:45 +0000, T i m wrote:

If that *is* likely to be an issue, IR would be ok as there is nothing
reflective, ...

Nothing reflective that you can see with visible light. Vegetation
reflects far more IR than it does red and blue light (which is why it
appears green). Grass verges look snow covered under IR.

... as could be basic PIR LED lamps to generally illuminate the scene.

If the camera switches fast enough and you can get the light levels
high enough. Also bear in mind any shadows or areas of lower
illumination are going to be dark or just black.

IR illumination avoids any camera mode switching, though there will
be a exposure issue if when you switch the IR on/off. Leaving the IR
on at low light levels is best. The camera is running at or near
maximum sensitivity so lower illuminated areas aren't completely
black.

I don't have a specific target / scenario in mind, just that the std
IR illumination with colour during the day and b/w at night must be
the norm for good reason?

"Colour" is defined the frequency of the lightwaves, so as IR is
outside the the range of frequencies of visible light it has no
colour. One can of course transpose a range of IR frequencies into
the visible range and create "false colour" images, as some thermal
image cameras do.

How covert do you want to be? 850 nm (ish) ("near infrared") IR
illuminators are visible as dull red glow. If you shift to 960 nm
(ish) the source is not visible but the sensitivity of most cameras
is noticably falling off by then.

--
Cheers
Dave.