Hoya ND8 / NDx400

[CB_Bebop]

Hi folks

I am struggling to source a Hoya NDx400 in South Africa.
I can however get an ND8 at a very attractive price.

2 questions:
1. How many ND8's would I have to stack together to get the same level as the NDx400? By my reckonning, 3.

2. Is there any downfall to stacking filters vs using 1 filter?

Thanks in advance

Anton

[CB_Bebop]

Seriously? Is there nobody that can advise me?
Did I post in the wrong section?

[Headshotzx]

No, this is the right sectoin.

I'm thinking more glass in front of the sensor will cause the image quality to degrade just that little bit. But since you want ndx400 I'm thinking you're already at f/22 or smaller where diffraction already takes place, causing images to be a little softer. if you're okay with that, you might still have to see if there will be vignetting. For most UWA's, 2 filters will already vignette (you'll see the filter).