Tech specs on ND filters??

[Marvin]

Does anybody know what the technical specs are on ND filters??. Like what do the numbers really mean??
It looks like there are 2 standards that get confused....:confused:

I first started using REALLY dark filters 11 years ago for eclipse viewing/photographing but I seem to have lost them and I never knew what the ND equivalent number was anyway.

I bought some welding glass that is pretty dark. Says "shade 10" but I guess it isn't the same as ND10.
I also bought a proper "ND4" filter and it seems very pale. So I purchased some proper 'solar' protection film and this is very black. But it only claims to be "ND5", allowing only 0.001% light transmission

A Fuji guide book states that a ND2 allows 1% of the light to pass through. ND3 = 0.1% and ND4 = 0.01%

Another 'solar' filter claims to be ND1024.

Yours sincerely,

Confused of Coventry :cool:

[miffy]

My apologies, Nige, as this is totally off topic, but now i've finished laughing fit to bust, i've just GOT to ask how you managed to slide so seamlessly from "The Wheeltappers & Shunter's Club", to typing out THIS post???? !!!!! :rofl::rofl::clap::rofl::laff:--Sorry, i'll stop now!!:o

xxjan

[benjiblanco]

lol Jan :D

I always just assumed Nigel the number was the fraction.

ie

ND1 = 1/1 = 100%
ND2 = 1/2 = 50% 1 stop reduction
ND4 = 1/4 = 25% 2 stop reduction
ND8 = 1/8 = 12.5% 3 stop reduction
etc etc

So an ND1024 would be 1/1024 = 0.098% or 10 stop reduction.

[Marvin]

Thanks Ben, that is what I always thought but there must be another set of numbers that some ppl are using. OR, as it is internet that I am reading, are they just making it up?? My very black ND5 solar filter IS from USA though - they probably work in old money (their gallons are smaller than ours!)

My ND4 matches those numbers that you state, it also explains why you don't see ND1 or less. I'll check all mine tomorrow and see what readings they give. My ND5 solar filter might be awkward though! Do digital sensors suffer reciprocity failure???? :D

I just saw another (British) site that sells ND3 filters that give a 10 stop reduction... Also says " They are available in 4 densities...ND 0.3, 0.6, 0.9, 1.2 and 3.0"

Those 4 densities are 5! Sorry, I can't trust a mathematician who can't count to 5! :headbanger:

[benjiblanco]

those numbers 4 or 5 of them :D would be the filter optical density!

ie, they are the absorbance, not the transmittance, hence they go up, ND1 = 0 absorbance.

[benjiblanco]

I just saw another (British) site that sells ND3 filters that give a 10 stop reduction...


Yep, if you used the fraction method, then it iis really ND1024, 10 stops but the optical aborbance would be 3.0 :top:

Starting at 0 it goes up in .3's hence 10 stop equals 3.0 :)

[benjiblanco]

:top:

[Marvin]

That makes sense for my ND5 that transmits around 0.001%.. :clap:


At last!! :carrot:

[benjiblanco]

i guess its easier than writing ND64,000, but thats what id call it lol or probably about ND100,000 thinking about it. :top:

[Marvin]

At midday today (bright overcast) it needed 30 secs, f4, 1200 ISO. But not a good quality though.. :(

[Cowden]

So Nigel does the film you ordered work.........have you tried it yet...? if so how did you use it and what was the outcome...cheers Keith:top:

[Marvin]

Need to do some more tests with it but so far I have found it 'disappointing'. Gives a foggy effect very good though! :(


I might be being a bit cruel on this stuff. It is VERY dark and I just might be getting some light behind it, perhaps through the VF, perhaps the filter holder.

I have glued a bit onto a stepping ring, ready to try again.....