IR Cut Filters - please help a quasi newbie

[Aengus4h]

old thread I know but in case its of interest to folk with cameras that have no IRcut filter so get purple colour on grass etc, I've just ordered a set of these
cctv lens camera filter , IR pass new 10 pcs lot 850NM-in CCTV Parts from Security & Protection on Aliexpress.com | Alibaba Group

Will give them a test when I get them and report back. Would be great if they give reasonable colour correction in daylight and can still support IR illimunators at 850nm. Plan is to install on the back of a M12 f1.4 2.8mm 6MP starlight lens and compare images against no filter and full IRcut on same spec lenses, assuming we'll get some bright sunny days here in the UK by the time they arrive that is ;-)

 

[Aengus4h]

OK so the 850nm filters arrived this morning so a little experimenting and...

Left is 2.8mm f1.4 with filter that is UV but passes IR, right is the new 400-850nm filter that should cut UV and IR only above 850nm.

still pink on foliage, oh well. Yeah I know the newly installed (right pic) is a touch out of focus, will sort that later. Will see how it fairs tonight once the IR comes on and if it lets that pass. Doesn't seem there's a work-around for a true mechanical IRcut filter but for a couple quid was worth a try as I do have several cameras that don't physically have room for one.

I had previously bought some supposedly IRcut round filters which is what's on the pic marked UV filter - seller said it cuts at 650nm but clearly it doesn't and in fact image is around the same as the new ones that cut off at 850nm as can be seen above.

A true IRcut filter glass on same model 2.8mm f1.4 starlight lens gives nice greens and clear sharp colours (front pic below). It was supplied with IRcut filter on the back by Treeye on request.



For now, the front view cameras have F1.4 & IRcut treeye lenses and with street lighting are fine for day/night without assist. The rear views will have to manage on with the colour shifted psychedelic "greens" as they do need IR assist, same for indoor ones...

I guess the only other option is a filter designed to pass 400-650 and then a notch pass for 850 or 940 to allow IR assist without needing a mechanical filter, tho never seen these on general sale and would likely be an expensive special order if you really wanted one.