IR filter for old home tube camera question

[Dave A]

A lens filter question. I have a 1978 RCA CC002 striped vidicon home color video camera with a gone-to-cloudy IR filter behind the lens...a common problem with the light blue fluorite material they used. 11mm x 15mm and long gone from anywhere. Without it, the camera focus goes bad and a massive red tint appears. Too much IR in the wrong focus hitting the tube. I can find 58mm filters for the front. Does it make a difference if the filter is in the front or does it need to be in the back of the optical path? When this thing works, it is a great 1978 image and easy to tune with a scope.

[old_tv_nut]

Should not make a difference if it's in front. Where do you find an external infrared-cut filter? That's not a common thing for photography.

Edit - I stand corrected - searched on Amazon and immediately found a Hoya filter that is both UV and IR (>700 nm) cutting.

[Tube TV]

Did you ever find one Dave? I did see a bunch of various sizes on ebay last year. I think they were shipping out of China. The larger sizes were more economical than the smaller ones, and it might have enough to make a few others depending on the size you need

Here's one I found doing a quick search
https://www.ebay.com/itm/26685631417...=&toolid=10050

and some smaller ones

https://picclick.com/Various-sizes-6...733102740.html

[ARC Tech-109]

That blue filter is also used by Sony professional cameras and is known to cloud over time. You can remove and replace it with a standard piece of glass as this also affects the focal path thus the reason for the focus issue. I don't know how effective an external IR filter would be or how sensitive the old vidicon tube is to infrared. The red tint is the result of the camera calibration to counter the blue filter and you will need to counter this.

[Dave A]

I did get a 58mm front filter and it did the trick. The new one is not as dense a blue as the old filter, but it got close enough that I could do some white level adjustments to get it right. The next time I have it out I will do the "aim a remote control at the lens" trick to answer the IR question.

[Dave A]

ARC, adding on to your note about the Sony glass. I picked up a DXC-3000 today for a $1.98 or so. The IR glass was bad as noted. I dug a similar one out from a later camera, but it was about 1mm thicker and the lens would not mount. I pulled it out and the camera works but focus is not correctible with the lens back focus adj. Way out of range. The Fuji lens having a clouded back element does not help. Glass IR optic needed, I guess. I tried my M3 Canon lens, but it was the same focus issue. I need to get a good Fuji A12x108-83 lens first and then try the filter trick unless I find a proper 3000 filter. Oh well, it was cheap.

[ARC Tech-109]

As I understand from my old service notes the glass assembly on the front is an apochromatic lens and has three dedicated elements to compensate for chromatic aberration so the blue didn't bloom or fringe from back focus tracking errors. All the elements together affect the overall focal depth so this is why it won't focus.

This was all outlined in I believe an Ikegami or JVC service manual I stuck my nose in decades ago when the pb tube was still king.