Drop-in filters for long lenses

[Frodo]

I'd like a roughly 3-stop ND filter for my 400 DOii to allow slower shutter speeds for panning photos. It came with the gelatin filter holder. I've heard mixed views on gelatin filters affecting sharpness. Has anyone had success using gelatin filters on long lenses?
In theory it is possible to get a drop-in screw filter holder that uses 52mm filters (provided they're not too wide or deep), but these seem impossible to find.
An alternative would be to get a drop-in filter EF-RF adapter. The genuine Canon one is quite expensive and for the relatively limited use it would get, I'm not keen to spend so much. There are 3rd party drop-in filter adapters, e.g. Meike and JJC. I have a set of Meike RF extension tubes, but the fit isn't great, even between two of their tubes - I wouldn't be happy to mount a heavy tele lens on it. I have a JJC normal EF-RF adapter (that I hollowed out to fit an RF 1.4x to my 400 DO) and that was quite well constructed.
So while I'd prefer a drop-in screw filter holder, I am interested in the JJC drop-in filter adapter (https://www.jjc.cc/index/goods/detail.html?id=2512)
Your thoughts appreciated.
Thanks

 

[kaihp]

The EF 400 DO Mk II takes a drop-in filter, right? - I found the B+W Filter 52mm ND 0.9 MRC Nano Master that fitted into the OEM screw-in adapter.
Note that many 52mm filters' OD is too large to fit into the drop-in slot.

PS: I'm getting a malware alert on that jjc(dot)cc link

 

[Frodo]

Hi kaihp
Yes, the EF 400 DOii takes drop in filters. The reason for the post, is that it is very difficult to find one as it appears they have been discontinued.
Thanks about the malware alert - I don't get one at that site.

 

[kaihp]

The screw-in drop-in filters could very well be discontinued. I found a new-in-box from a 2nd hand retailer in France a couple of years back. He doesn' have it in stock right now, though.
I was looking for an ND3 as well at the time. I now have a clear, an ND3, and a C-POL.

 

[Frodo]

The screw-in drop-in filters could very well be discontinued. I found a new-in-box from a 2nd hand retailer in France a couple of years back. He doesn' have it in stock right now, though.
I was looking for an ND3 as well at the time. I now have a clear, an ND3, and a C-POL.

Yes, I bought a Kirk lens foot from them. They wouldn't ship to New Zealand, but I got it via my brother-in-law in Switzerland.