ND filters-clarification please

dinneenp

Hi,
I'm looking to buying a cheap ND filter. (Cheap because not sure would I use one a lot so I'll buy a cheap one to begin with). To fit 62mm

On Ebay here the person is selling a NEW 62mm ND Filter Set Neutral ND4+ND8.

Is the ND4 stronger/darker than a '10 stop nd filter'? I presume so.
But then a ND8- that seems crazily dark?
Cheers,
Pa.


Graduated ND 0.3 – 2x (#501)
Graduated ND 0.6 – 4x (#502)
ND 0.3 – 2x (#101) ~ 1 stop
ND 0.6 – 4x (#102) ~ 2 stops
ND 0.9 – 8x (#103) ~ 3 stops
ND 1.8 – 64x (#106) ~ 6 stops
ND 3.0 – 1000x (#110) ~ 10 stops

smelltheglove

I have an ND4 and Im pretty sure an ND6 would be stronger than the 4 and so on. The higher the number the higher the strength.



WIKI link http://en.wikipedia.org/wiki/Neutral_density_filter

kelly1

Looks like different manufactures use different designations:

http://www.great-landscape-photography.com/neutral-density-filter.html

I don't know why they don't just indicate the number of stops.

PopeBuckfastXVI

ND8 is normally 3 stops, ND4 is 2, and ND2 is 1.

Naturally!

kelly1

So how many stops is ND10?

PopeBuckfastXVI

kelly1 wrote: »

So how many stops is ND10?

You can get a 10 stop ND filter, maybe someone has one branded as ND10? I don't know because I've not seen it.

Branding above is the cokin system, by the way. Others may vary.

Edit: see below

PopeBuckfastXVI

http://en.wikipedia.org/wiki/Neutral_density_filter

FoxT

I think the science goes like this:

An NDx filter will let in 1/x of the light available.

So, an ND2 filter will let in 1/2 the light, an ND10 filter will let in 1/10th of the light, etc.

Now, every time you reduce the light intensity by a stop, you are reducing the amount of light available by 1/2.

So, an ND2 filter lets in 1/2 the available light = 1 stop.

An ND4 lets in 1/4 (= 1/2 x 1/2) so that is 2 stops.

In General, an NDx filter = Log(x) stops (to base 2)

So an ND10 filter is about 3.3 stops.

A 10 stop filter would then be ND1024.

BUT - different manufacturers label their filters differently - so read the small print before you buy!

kelly1

I've heard the Lee Big Stopper referred to as an ND10 on a few sites. Just checking the Lee website, they use 0.3 for 1 stop, 0.6 for 2 stops and 0.9 for 3 stops. So it looks like there is no such thing as an ND10 and it's actually the wrong name for what is really a 10-stop ND1024. You live and learn!

FoxT

Confusing issue is confusing!

A 0.3 filter = a 1-stop filter, because -log(1/2) = 0.3!

Ahh, yes, logarithms...

To be fair, the Wikipedia article linked above is pretty comprehensive.