Which ND filter I need?

[Dacon Productions]

I fly in AZ (sunny and clear skies) and only shoot in 1080P/60.
Which ND is really needed? ND8 or ND16? Shutter speed is 120 - 140.

 

[John Locke]

Usually ND16 works well in bright desert sunlight. You'll want to target 120 shutter speed when shooting 60fps. If it is 180 shutter speed or higher with nd16, try nd32 to slow it down more.

 

[snerd]

-------^^^^^^^^ What he said.