Neutral density filters
ronv...@gmail.com
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?
Ray Fischer
The article explained how they are not perfect. If you cited the
article then you should have read it.
--
Ray Fischer
rfis...@sonic.net
ronviers
equally".
In what way? What casts can be expected? When Photoshop emulates a nd
filter, what is being changed?
How are they not perfect?
Ray Fischer
>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"
--
Ray Fischer
rfis...@sonic.net
Troy Piggins
> It just says, "they do not reduce the intensity of all
> wavelengths equally".
>
> In what way? What casts can be expected?
I've read that some cheaper ND filters give a purple/magenta
cast. This can be corrected with typical white balance post
processing.
> When Photoshop emulates a nd filter, what is being changed?
> How are they not perfect?
I don't use PS, but assume that "emulating" is just dropping the
exposure? ie darkening the image?
PS can't always emulate a ND filter. ND filters increase the
exposure time for the same aperture and ISO. This can be used
for effect for things like running water or clouds that move -
gives that milky/streaky sort of effect such as this:
http://marcopolo17.deviantart.com/art/Cold-wind-81015165
http://marcopolo17.deviantart.com/art/The-race-86041823
You can't emulate that in PS.
--
Troy Piggins
ronviers
>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?
Neil Ellwood
>>"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.
--
Neil
reverse ra and delete l
Linux user 335851
bugbear
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.
BugBear
Don Stauffer
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.
Ray Fischer
>>"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
rfis...@sonic.net
Ray Fischer
>>"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
rfis...@sonic.net
George Kerby
On 5/27/09 1:33 AM, in article
966cffea-e295-4c2a...@y7g2000yqa.googlegroups.com, "ronviers"
<ronv...@gmail.com> wrote:
"Why is there air?"
SneakyP
news:fdOdneatDoT9iIDX...@bt.com:
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)
SneakyP
news:J92dna2lGqp3ioDX...@brightview.co.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).
Peter Irwin
>>
> 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).
>
block the reds. They are available in various strengths.
Peter.