Just wanting to know if anyone has taken the Fujinon 17x 1/3 lens apart before. Have some dust in mine and may send it in for an estimate (ball park $500-$1,000) for disassembly, clean repair etc. Anyway hoping it's behind the primary glass. Any experience out there?

I have never and I mean never touched any lens in that way. I think it might be illegal in 32 states ;-)

I would seriously recommend you leave best be and not attempt any surgery, especially if you are a learner-driver in lens repair. There is so, so much to get wrong. - You will likely introduce more problems than you solve and much more fine contamination faster than you can clean it out. Unless there are dust motes on the inside of the element closest to the camera, it should still be fine. This is not say you cannot do it but anywhere this side of a laboratory standard clean-room is going to leave you with more difficulties than you can handle.

The little guys in Japan put a considerable amount of effort into getting it right. It is a pity when people disrespect their good work by tinkering and ending up with an icecream container of loose bits going out into the wheelie bin next spring-clean.

Dust on the inside of the rear element may show as donut or pimple artifacts in the image when you are in bright outdoors and forced to close the lens iris to its tightest. It will be most evident against a hard sky when following such as birds or aircraft in flight. At more sensible iris settings, the dust motes should not be evident.

At iris f5.6 or higher numbers you may be entering a zone where diffraction becomes an issue. My personal preference is to use ND to maintain the lens iris in the zone f4 to f6.3.

If your in-camera ND is not dark enough, you might consider using ND in front of the lens and maybe an IR filter. IR contamination in the blacks has been an issue with the JVC GY-HD*** camera family when heavy ND has been used. The issue is not unique to the JVC.

Use ND to keep the lens in its sweeter zone and you will not only avoid the pimples but also add aesthetic value as a collateral benefit.

Please heed the comments of other more qualified to comment than I.