[Nogbad]

Hi all, have a question but seems a bit silly.

Anyway here goes.

I am wanting to take some images on my holiday into Wales in the next few weeks.

I want to slow the shutter down to obtain the desired "Milky" appearance of the flowing water.

I understand the concept of the shutter speed, aperture etc, and using an ND filter to give additional stops to acheive this.

However do I compose the image first and then put the filter on. Or do I put the filter on and then compose the image. or does'nt it matter? Silly question I know!

One more thing which density ND filter is best to use?
Thanks

Nogbad