Cheap ND Filters

[Doug]

After playing around with the welding glass it got me searching for a CHEAP filter that I could harvest to create a more solid welding glass filter.

And I came across loads of ND filters (Going up to 8) for peanuts.

See link here....

The list of 'pros' as I see it:
The optical quality of these cannot be any worse than the welding glass
They apparently do not affect the colour balance (unlike the welding glass!)
They are easier to use (just screw on)
Pretty cheap.

Would a ND8 be rubbish for long exposures in the daytime? I suppose you could stack a couple ND filters to get to ND10.

Is there a reason why no-one uses these E-bay cheapies to see if they really like the idea of ND's before taking the plunge and buying properly?

 

[The Matt]

yeah they would most likely be rubbish for it. An ND8 filter is only 3 stops and the welding glass is 10 or more stops. You'd need 3 or 4 of those cheapies to get the same effect. Stacking them causes any colour cast (and I would be absolutely amazed if they didnn't have one. All but the best have one, despite the advertising blurb) to be amplified. The image quality also degrades with each additional filter. You would get a pretty dire image.

Remember when you're buying filters there's three ways to number them:

Filter       Optical      F-stop
Factor     Density     Reduction
ND2           0.3             1
ND4           0.6             2
ND8           0.9             3
ND64          1.8             6
ND1000        3.0             10

So ND8 is nowhere near 10 stops unfortunately.

 

[Doug]

Ahhhhhhh I knew there would be a reason behind it!

 

[LongLensPhotography]

yeah they would most likely be rubbish for it. An ND8 filter is only 3 stops and the welding glass is 10 or more stops. You'd need 3 or 4 of those cheapies to get the same effect. Stacking them causes any colour cast (and I would be absolutely amazed if they didnn't have one. All but the best have one, despite the advertising blurb) to be amplified. The image quality also degrades with each additional filter. You would get a pretty dire image.

Remember when you're buying filters there's three ways to number them:

Filter       Optical      F-stop
Factor     Density     Reduction
ND2           0.3             1
ND4           0.6             2
ND8           0.9             3
ND64          1.8             6
ND1000        3.0             10

So ND8 is nowhere near 10 stops unfortunately.

In your table 10 stops is ND1000, not ND10. Following this logic ND10 would be around 4 stops. You can add CPL on top, set ISO 100 f/16 and in the afternoon it would be easily as slow as a few seconds.

 

[HoppyUK]

In your table 10 stops is ND1000, not ND10. Following this logic ND10 would be around 4 stops. You can add CPL on top, set ISO 100 f/16 and in the afternoon it would be easily as slow as a few seconds.

Using two ND8 filters would give you ND16, which is 4 stops. A polariser on top would give up to 2 more, so 6 stops max.

Using Sunny 16 rule at ISO100, would reduce 1/125sec to 1/2sec. Obviously longer on a cloudy day. But stacking three filters together is not a good plan, and three cheap ones is a bad plan, plus vignetting problems for sure even on a modestly wide lens.

Seems to me the best 'economy' ND filter is the welding glass, with custom white balance to get rid of the green cast (works well). The only alternative is to buy a B+W ten stop filter.

 

[LongLensPhotography]

Using two ND8 filters would give you ND16, which is 4 stops. A polariser on top would give up to 2 more, so 6 stops max.

Using Sunny 16 rule at ISO100, would reduce 1/125sec to 1/2sec. Obviously longer on a cloudy day. But stacking three filters together is not a good plan, and three cheap ones is a bad plan, plus vignetting problems for sure even on a modestly wide lens.

Seems to me the best 'economy' ND filter is the welding glass, with custom white balance to get rid of the green cast (works well). The only alternative is to buy a B+W ten stop filter.

ND8 must be OK for work in the afternoon or early in the morning (a couple hours before sunset / after dawn). Midday is the most problematic time of the day... Mostly the brave people with advanced P&S cameras work under these conditions

P.S. What about this one http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=250487473801&ssPageName=STRK:MEWAX:IT ? They claim it is made of optical glass (instead of plexiglass like HK ones)