Tony M May 14, 2011:

That's my point, Alain If this is the proper name of one particular manufacturer's product, then that's fine; my only query was if this is a generic term, does this mean terminology has changed, or is this another error in the source text — or is it in fact that this particular variant of the term is used in certain specific fields; just as, for example, digital photography has invented 'new' terms for many things in traditional photography.
Hence my question, as to whether this is perhaps specifically in connection with an accessory for a digital camera, for example.

Alain Marsol May 14, 2011:

> Tony: Brands of filter manufacturers. The name itself shows what the context is about, and Véronique has confirmed ;)

Véronique Le Ny (asker) May 14, 2011:

NDX4X is the name of a filter for lens.
Merci beaucoup!

Tony M May 14, 2011:

Thanks Alain! But brands of... what? We seem to be missing a bit of context here...

I guess this must be more recent terminology, then, in a specific field.

Alain Marsol May 14, 2011:

As far as I know, several brands have a ND4X, so it looks more like a noun to me...

Tony M May 14, 2011:

Bad English I think the poor quality of this apparently non-native EN is probably not helping your understanding here!

Certainly, the comma after aperture doesn't help a bit, and I would suggest reading it as if there were no comma.

Is ND4X the model number of their specific piece of equipment? If not, note that 4× is not the usual way of expressing ND filters, which are normally given as 0.3, 0.6, 0.9 etc. (system analogous to the use of logarithmic dB, where 0.3 = –3 db = 50% = –1 f stop)