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Thread: ND filters

  1. #1

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    ND filters

    Was at a shop yesterday that sells photographic accessories and while looking over their large collection of 3rd party Cokin/Lee style filters noticed that as knock-offs they did not have a 10 stop ND - only 2, 4, 8. There were also a huge variety of coloured filters.

    Anyway noticed a ND 16.

    A 10 stopper is already pretty intense and people seem to get good results from it.

    Under what circumstances would one want to use a 16?

    About the rating - does the ND number equate to the actual number of stops or is there some other formula?
    Last edited by Bobobird; 18th April 2012 at 04:20 AM.

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    Re: ND filters

    I'd think you'd just about be into photographing the surface of the sun with one of those! (not a suggestion). In all seriousness, I suspect that you'd be able to smooth water in the middle of the day - I'd guess you'd be able to use about a 30 second exposure @ F4 on a sunny 16 day with one.

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    Re: ND filters

    I just got a Hoya NDx400 9 stop filter a couple of weeks ago. It's intense and even this 9 stop can be used to photograph the surface of the sun or a solar eclipse, as it reduces the light level to 1/500th of the original brightness. I have used it to turn waterfalls into flowing silk. Amazing stuff... but, a 16 stop? Wow... I would think that would be used for solar photography only. I have never heard of such a beast. I had to Google it just now and I can't find a 16 stop. However, I did find a Hoya 16x which reduces the light by 4 stops. Come to think of it, I have never heard of a filter going past 10 stops.

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    Re: ND filters

    The usual notation on ND filters is not the number of stops, but how many times exposure must be prolonged. So a ND 16 is a four stop filter.

    The ND 16 might be a good comprimise for many situations where ND is required. Usually I recommend ND8 as a filter for using a larger F-stop and ND64 for longer shutter times, and they may be combined if you want a really long shutter time. ND16 gives you possibility to use a really large f-stop to get short DOF, and it may also be used for combining short DOF with a reasonable long time to get panning effects. Still for eliminating anything that moves and creating the fog-like effect of moving water, it might be insufficient.

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    Administrator GrumpyDiver's Avatar
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    Re: ND filters

    I've run across two different numbering systems for ND filters and wonder if this might be part of the confusion. One numbering system is based on the reduction of the amount of light that is transmitted while the other is based on the equivilent f-stop reduction. The only way to know which system is being used is to look at the optical density rating of the filter.

    I remember looking at two different filters that had the same optical density of 0.9. One was labeled as an ND8 and the other as an ND3. I suspect you are used to one numbering system and the manufacturer you were looking at was using the other

  6. #6
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    Re: ND filters

    This link

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

    shows the relationship between the ND number and f stops, but as Manfred has noted there are different ways of labelling ND filters.

    Dave

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    Re: ND filters

    We always talk about quality of glass filters but, seldom talk about the quality of square filters. I know that the Singh Ray filters, Colin works with, are of excellent quality but, I just wonder about less expensive square filters such as Cokin? It seems hard to imagine that the plastic type material of these filters will give the same image quality as a multi-coated optical glass filter.

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    Re: ND filters

    Quote Originally Posted by rpcrowe View Post
    We always talk about quality of glass filters but, seldom talk about the quality of square filters. I know that the Singh Ray filters, Colin works with, are of excellent quality but, I just wonder about less expensive square filters such as Cokin? It seems hard to imagine that the plastic type material of these filters will give the same image quality as a multi-coated optical glass filter.
    Many years ago I had an extensive Cokin system, and now I have only one filter, a graduated grey filter, which I think is better than the other one I had many years ago, which was round and had the division somewhere in the middle.

    The advantage of the Cokin graduated filter is that it may be installed at varying distances from the lens, and that it may be positioned at another height than with the division between clear and ND in the middle. The disadvantage, that it has no AR coating whatsoever. It does cause a halo-like double line on the edge of any line that is not exactly in the middle or running radially out from the middle. Much care must be taken not to get this property intrusive. For example, taking a building and using the filter not to over-expose the upper storeys and the sky, may cause windows on upper storeys and the top of the building to double, which is rather annoying.

    I have been told that Lee filters made of glass should be better, but I haven't tried any. The Cokin filter is optically rather flat, but it does cause artifacts by reflections from both surfaces. Often it will go unnoticed, but under certain conditions it is clearly visible and obtrusive.

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    Re: ND filters

    Quote Originally Posted by rpcrowe View Post
    We always talk about quality of glass filters but, seldom talk about the quality of square filters. I know that the Singh Ray filters, Colin works with, are of excellent quality but, I just wonder about less expensive square filters such as Cokin? It seems hard to imagine that the plastic type material of these filters will give the same image quality as a multi-coated optical glass filter.
    Hi Richard,

    Many of the cheaper ones have issues in the infrared spectrum that can give you an orangy/red cast that can be VERY difficult to null completely.

  10. #10
    Administrator GrumpyDiver's Avatar
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    Re: ND filters

    Quote Originally Posted by Colin Southern View Post
    Hi Richard,

    Many of the cheaper ones have issues in the infrared spectrum that can give you an orangy/red cast that can be VERY difficult to null completely.
    When it gets to Grad filters, all the ones I have (Heliopan and B&W) are plastic. I think pretty well all of them are made that way, but I think I read somewhere that Tiffens are not (I suspect that they are actually plastic sandwiched between two piece of glass) much like polarizers are.

  11. #11
    William W's Avatar
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    Re: ND filters

    Quote Originally Posted by Bobobird View Post
    About the rating - does the ND number equate to the actual number of stops or is there some other formula?
    Another way of expressing the formula is -

    2^y = S

    Where:
    y = the number of stops the filter reduces the exposure
    S = “ND Number”

    Therefore, as already mentioned, and ND16 is a 4 stop filter, because 2^4 = 16 (i.e. 2 x 2 x 2 x 2 = 16)

    ***

    Other stuff:

    An ND400 filter is actually (about) an 8⅔ Stop filter, but is usually referred to as a 9 Stop Filter.

    I do not know of any Photographic Filter, stronger than ND400

    A 16 Stop Filter would be an ND65536 – but it would be more likely labelled "ND65000" or "ND66000", if one existed.

    An ND400 Filter is quite dark: focusing is made, before the filter is attached.
    ND filters

    ***

    More stuff

    Welder's (protective) Glass is designated by the "Shade" and nowadays comes in Shades (designated by DIN Standards) from 4 to 14.

    Grade 4, being the least protective and Grade 14 being the strongest, or most protective.

    As a rough guide, a Grade 10 Welder's Glass is about equivalent to 12~14 stop ND Filter: and Welder’s Glass Grade 14, is a little stronger than what a 16 Stop ND Filter would be – sort of.

    I add the “sort of”, because Welder’s Glass also has a tint - these filters usually have a thin layer of aluminium, chromium or silver which attenuates the ultraviolet, visible, and also the infrared spectrum (the tint is usually Gold or Green), and this has to be removed in post production (or maybe not).

    Welder’s glass is relatively cheap and quite fun with which to experiment, for long exposures.

    ***

    REALLY IMPORTANT NOTE -

    I would warn that extreme care AND Specialized Knowledge and data be sourced, before photographing Solar Eclipses or the Surface of the Sun.

    NO Photographic Neutral density filter - not even an ND400 - offers adequate eye protection for such an endeavour.


    WW
    Last edited by William W; 18th April 2012 at 06:40 PM. Reason: added "REALLY IMPORTANT NOTE"

  12. #12
    Administrator GrumpyDiver's Avatar
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    Re: ND filters

    Quote Originally Posted by William W View Post
    An ND400 filter is actually (about) an 8⅔ Stop filter, but is usually referred to as a 9 Stop Filter.

    I do not know of any Photographic Filter, stronger than ND400

    WW
    Actually ND1024 / ND10s are fairly readily available. My 77mm B&W is at that optical density and I know that Heliopan make one that size and density as well. You are quite right on using it. Set everything up on the tripod, install the filter and shoot. Very little light gets through it.

  13. #13
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    Re: ND filters

    I would warn that extreme care AND Specialized Knowledge and data be sourced, before photographing Solar Eclipses or the Surface of the Sun.

    NO Photographic Neutral density filter - not even an ND400 - offers adequate eye protection for such an endeavour.
    True, and I guess it must be said. I'm sure there is someone out there who will try looking directly into the sun. The only safe way to photograph the sun with an ND filter is to use live view. No live view, then don't try it.

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    My idea...

    All round GND filters seem to have the demarcation line straight through the center of the filter, forcing you to place your horizon through the center of your image (boring the viewer and shooter alike).

    Why not have the demarcation through 1/3 of the filter which would allow a photographer to use the rule of thirds?

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    William W's Avatar
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    Re: ND filters

    Quote Originally Posted by GrumpyDiver View Post
    Actually ND1024 / ND10s are fairly readily available. My 77mm B&W is at that optical density and I know that Heliopan make one that size and density as well.
    I didn't know that, thank you. I'll reseach if they make an 82mm size.

    WW

  16. #16

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    Re: ND filters

    William I would also suggest that you research Lee Filters from the United Kingdom, one holder and a sizing ring from your lens to hold it.

    Cheers:

    Allan

  17. #17
    William W's Avatar
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    Re: ND filters

    Quote Originally Posted by Polar01 View Post
    I would also suggest that you research Lee Filters from the United Kingdom, one holder and a sizing ring from your lens to hold it.
    Thank you.

    WW

  18. #18

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    Re: ND filters

    Thanks guys, lots of nfo to digest.

    Btw - STAY AWAY FROM KNOCK-OFFS.

    I went back to the shop yesterday and borrowed one of their tripods and tried out the ND8 and ND16. Pics turned out a deep RED. Took the pics home and no way ACR would color-correct them. The only option was b&w.

    Stuck on my Cokin ND8 and it worked just fine.

    So - STAY AWAY FROM KNOCK-OFFS.

  19. #19

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    Re: My idea...

    Quote Originally Posted by rpcrowe View Post
    All round GND filters seem to have the demarcation line straight through the center of the filter, forcing you to place your horizon through the center of your image (boring the viewer and shooter alike).

    Why not have the demarcation through 1/3 of the filter which would allow a photographer to use the rule of thirds?
    Hi Richard,

    To be honest, it may "increase the hit rate" but isn't likely to be ideal. Often I have mine set 2/3 of the way down (to retard the sky and it's reflection in water). IMO it's easiest to simply use sliding ones.

  20. #20

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    Re: ND filters

    Quote Originally Posted by Bobobird View Post
    Thanks guys, lots of nfo to digest.

    Btw - STAY AWAY FROM KNOCK-OFFS.

    I went back to the shop yesterday and borrowed one of their tripods and tried out the ND8 and ND16. Pics turned out a deep RED. Took the pics home and no way ACR would color-correct them. The only option was b&w.

    Stuck on my Cokin ND8 and it worked just fine.

    So - STAY AWAY FROM KNOCK-OFFS.
    Quote Originally Posted by Colin Southern View Post
    Many of the cheaper ones have issues in the infrared spectrum that can give you an orangy/red cast that can be VERY difficult to null completely.
    Told you so

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