thanks for the follow up, now I pose a few questions to you. Can I use a cpl filter on my converted D70? will it cause problems? And ND filters as well? Will the images start to deteriorate if I add anything to the lens? Or use as is? Also my 720nm, can I use a 520nm or no? I'm thinking I can go higher not lower than the installed filter. Happy belated New year btw
There are CPLs that work in IR, but I don't think any of mine do. Most normal filters (including CPLs & NDs) are fairly transparent above 750 to 800nm they'll have minimal affect on your 720nm converted camera.
Yes you're right you can go higher. Basically your conversion blocks everything below 700nm adding a red filter would have the red filter block below 550nm but the bit that gets past is still blocked internally to ~700nm
When playing with unmodified cameras for IR, I find it's pointless using anything less than 720nm, the visual portion that gets through will completely swamp any IR. The effectiveness of stock cameras is very variable, some can manage IR handheld shots, other struggle to see any IR at all. I believe your D70 before conversion would have been roughly the same as my K100d just about capable of hand held IR. One big advantage of the conversion on that is you can see through the viewfinder - I can't with the K100d when it's fitted with a 720nm filter one reason why mirrorless has a big advantage for IR.
If you have more follow up questions it might be best to ask on the
extended spectrum gear portion of the forum. I'm fairly sure to see any post there, as will others who shoot IR & the replies will be easier to find in the future.
Happy new year to you too! At least I've managed to get a good start in my photographic hoarding, picking up several lenses & an adapter I was after from a local charity shop today. I should now be able to mount my M42 fisheye via a variable ND (behind the lens) to get IR only results from a lens that can't take filters. I think everything I picked up at the charity shop was less than 1/3 the price on e-bay and there's no need to wait for delivery.