Help Regarding ND400

I think it's about time that I invest in a Hoya ND400. I really am fond of shooting landscapes and I think I would really be able to put this nd400 to good use.

My problem however is that I use the 18-55mm kit lens for shooting landscapes. The focusing ring of this lens is in front, where you screw in the filters. According to what I've read, you have to focus the image before putting on the filter since you basically won't be able to see anything with the nd400 attached. My fear is that if I do this, the focus will basically be changed when I screw in the filter and I'll have a hard time capturing an image in proper focus.

Would you still recommend that I get this ND400? Is there any way around this that you guys could share with me? Thank you for any insights you might be able to share with me.

Do you have any other filters you can try this on before you buy the ND400? If you leave the lens on auto focus while screwing on the filter, maybe it will be enough to stop the focus ring from moving, then you can switch to manual focus after (but the actual focusing has been done before).

I tried doing this with another filter a while ago. I guess I'll just have to hold the focus ring firmly while screwing in the filter in order for it not to move then switch it to MF afterwards.

Yeah probably the best you can do. It would be great if the focus distance was displayed on the LCD so you could use this to manually focus. Would also be handy for focusing at the hyperfocal distance.