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Neutral density filters

 
 
ronviers@gmail.com
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      05-27-2009
I was reading on wiki:
http://en.wikipedia.org/wiki/Neutral_density_filter
that neutral density filters are not perfect.

Can someone give me a simple explanation for why and how they are not
perfect, and a brief description of how they are made?
 
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Ray Fischer
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      05-27-2009
http://www.velocityreviews.com/forums/(E-Mail Removed) <(E-Mail Removed)> wrote:
>I was reading on wiki:
>http://en.wikipedia.org/wiki/Neutral_density_filter
>that neutral density filters are not perfect.
>
>Can someone give me a simple explanation for why and how they are not
>perfect, and a brief description of how they are made?


The article explained how they are not perfect. If you cited the
article then you should have read it.

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Ray Fischer
(E-Mail Removed)

 
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ronviers
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      05-27-2009
It just says, "they do not reduce the intensity of all wavelengths
equally".

In what way? What casts can be expected? When Photoshop emulates a nd
filter, what is being changed?
How are they not perfect?


 
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Ray Fischer
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      05-27-2009
ronviers <(E-Mail Removed)> wrote:
>It just says, "they do not reduce the intensity of all wavelengths
>equally".
>
>In what way? What casts can be expected?


It depends upon the particular filture and the manufacturer. Try to
use some common sense.

> When Photoshop emulates a nd
>filter, what is being changed?


Photoshop reduces the intensity. It is not a filter.

>How are they not perfect?


"they do not reduce the intensity of all wavelengths equally"

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Ray Fischer
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ronviers
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      05-27-2009
>"It depends upon the particular filture and the manufacturer. Try to
>use some common sense."


In other words, you do not know.

>"Photoshop reduces the intensity. It is not a filter."


Using the Photoshop adjustment layer 'Black and White' there is a
*filter* option 'Neutral Density'. It does not affect the colors
evenly. Does the uneven distribution correspond to predictable
imperfections from nd filters?

>"they do not reduce the intensity of all wavelengths equally"


In what way? What casts can be expected?


 
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Don Stauffer
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      05-27-2009
(E-Mail Removed) wrote:
> I was reading on wiki:
> http://en.wikipedia.org/wiki/Neutral_density_filter
> that neutral density filters are not perfect.
>
> Can someone give me a simple explanation for why and how they are not
> perfect, and a brief description of how they are made?


Some may not be perfectly "neutral". They may have some "color" to
them. Also, there might be a slight transmittance variance across them.

However, these effects are very minor. Any reputable brand of ND filter
will give you no substantial problems. Go ahead and buy a set.

There are two kinds. In one an absorbing substance is dissolved in the
glass. In the other kind, generally used for VERY high attenuation, a
thin metallic film is deposited on the surface of a clear glass.
 
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Ray Fischer
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      05-27-2009
ronviers <(E-Mail Removed)> wrote:
>>"It depends upon the particular filture and the manufacturer. Try to
>>use some common sense."

>
>In other words, you do not know.


Quite whining because you're stupid.

>>"Photoshop reduces the intensity. It is not a filter."

>
>Using the Photoshop adjustment layer 'Black and White' there is a
>*filter* option 'Neutral Density'.


It. Is. Not. A. Filter. It is a program which reproduces the effects
of filters.

> It does not affect the colors
>evenly.


And if you already know the answer to the question then why are you
asking?

> Does the uneven distribution correspond to predictable
>imperfections from nd filters?


"It depends upon the particular filter and the manufacturer."

>>"they do not reduce the intensity of all wavelengths equally"

>
>In what way? What casts can be expected?


"It depends upon the particular filter and the manufacturer."

--
Ray Fischer
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Ray Fischer
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      05-27-2009
ronviers <(E-Mail Removed)> wrote:
>>"It depends upon the particular filture and the manufacturer. Try to
>>use some common sense."

>
>In other words, you do not know.


Quit whining because you're stupid.

>>"Photoshop reduces the intensity. It is not a filter."

>
>Using the Photoshop adjustment layer 'Black and White' there is a
>*filter* option 'Neutral Density'.


It. Is. Not. A. Filter. It is a program which reproduces the effects
of filters.

> It does not affect the colors
>evenly.


And if you already know the answer to the question then why are you
asking?

> Does the uneven distribution correspond to predictable
>imperfections from nd filters?


"It depends upon the particular filter and the manufacturer."

>>"they do not reduce the intensity of all wavelengths equally"

>
>In what way? What casts can be expected?


"It depends upon the particular filter and the manufacturer."

--
Ray Fischer
(E-Mail Removed)

 
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SneakyP
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      05-28-2009
Neil Ellwood <(E-Mail Removed)> wrote in
news:(E-Mail Removed):

> On Wed, 27 May 2009 00:44:57 -0700, ronviers wrote:
>
>>>"It depends upon the particular filture and the manufacturer. Try to
>>>use some common sense."

>>
>> In other words, you do not know.

> He does know, he wants YOU to think for yourself.
>>
>>>"Photoshop reduces the intensity. It is not a filter."

>>
>> Using the Photoshop adjustment layer 'Black and White' there is a
>> *filter* option 'Neutral Density'. It does not affect the colors evenly.
>> Does the uneven distribution correspond to predictable imperfections
>> from nd filters?

> Try it and find out.
>>
>>>"they do not reduce the intensity of all wavelengths equally"

>>
>> In what way? What casts can be expected?

> Think - filters are made by differing manufacturers and have varying
> characteristics.
>
>

I think the OP has a neURal density filter applied to his brain.




--
SneakyP
To reply: newsgroup only, what's posted in ng stays in ng.

Some choose to swim in the potty bowl of nan-ae rather than flush it
down :0)
 
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SneakyP
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      05-29-2009
bugbear <bugbear@trim_papermule.co.uk_trim> wrote in
news:(E-Mail Removed) o.uk:


> Interestingly, one could (in theory) make a close-to-perfect
> ND filter FOR A PARTICULAR camera by using equal densities
> of the filter materials used in the bayer matrix of the camera.
>
> It would not affect *all* wavelengths equally, but (of course)
> in a three colour camera, only three wavelength (groups)
> matter.
>

That would bring up an interesting matter.

Is there a filter that will partially block the reds. I find that too much
red will oversaturate the receptors and make it appear yellow (at least in
my camera).


--
SneakyP
To reply: newsgroup only, what's posted in ng stays in ng.

Some choose to swim in the potty bowl of nan-ae rather than flush it
down :0)
 
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