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Polarizers and digital

 
 
Geoff Bryant
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      01-03-2004
After many years shooting transparency film I made the switch to digital
last August. I'm more than happy with the results but one thing intrigues me
and perhaps someone here can enlighten me.

Clearly cameras follow the same optical laws regardless of the capture
medium, but I've noticed that with digital filters seems to have less
effect.

I can understand this with coloured filters that may be negated somewhat by
automatic white balance, but what intrigues me is how the virtual trade mark
effect of a polarizer - deep blue to almost black skies - seems so much
reduced.

Yesterday I took some test shots with my 10D. It's midsummer here in the
southern hemisphere and the sky was clear blue with a just a very few pure
white clouds. The polarized shots certainly showed sharper contrast between
the clouds and the sky and the colours of the grass and other foliage were
brighter because of the reduced reflection. However, the colour of the sky
hardly changed; certainly not to the extent that I observed through the
viewfinder. With film it would probably have gone the other way - a far
greater effect.

Is this really the case or am I missing something?

Geoff Bryant
www.hortiphoto.com




 
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Don Coon
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      01-03-2004

"Geoff Bryant" <(E-Mail Removed)> wrote in message
news:N_qJb.57$(E-Mail Removed)...
> After many years shooting transparency film I made the switch to digital
> last August. I'm more than happy with the results but one thing intrigues

me
> and perhaps someone here can enlighten me.
>
> Clearly cameras follow the same optical laws regardless of the capture
> medium, but I've noticed that with digital filters seems to have less
> effect.
>
> I can understand this with coloured filters that may be negated somewhat

by
> automatic white balance, but what intrigues me is how the virtual trade

mark
> effect of a polarizer - deep blue to almost black skies - seems so much
> reduced.
>
> Yesterday I took some test shots with my 10D. It's midsummer here in the
> southern hemisphere and the sky was clear blue with a just a very few pure
> white clouds. The polarized shots certainly showed sharper contrast

between
> the clouds and the sky and the colours of the grass and other foliage were
> brighter because of the reduced reflection. However, the colour of the sky
> hardly changed; certainly not to the extent that I observed through the
> viewfinder. With film it would probably have gone the other way - a far
> greater effect.
>
> Is this really the case or am I missing something?
>
> Geoff Bryant
> www.hortiphoto.com


Not sure if you're missing anything but I must say a circular polarizer
works well on my 10D --- sometimes too well : ) --- skies that are too
blue. Keep working with it; it works. Now, if you could just send some of
that nice summer sun North -- it's dark by 5 PM her in the northern 48 of
the USA.


 
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Jim Townsend
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      01-03-2004
Geoff Bryant wrote:

> After many years shooting transparency film I made the switch to digital
> last August. I'm more than happy with the results but one thing intrigues me
> and perhaps someone here can enlighten me.
>
> Clearly cameras follow the same optical laws regardless of the capture
> medium, but I've noticed that with digital filters seems to have less
> effect.


Are you using a circular polarizer ?? If so, you shouldn't see any
difference. All the 'polarizing' is done before the light hits the film or
sensor.

I have a 10D and use a polarizer now and then.. Just as Don Coon indicates..
They work fine on digicams..


 
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Geoff Bryant
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Posts: n/a
 
      01-03-2004
Yes, I'm using a circular polarizer. And yes, it works. But although I can
see the effect, it doesn't seem nearly as extreme as with film, where the
sky well above the horizon can become a really deep indigo blue. That
doesn't worry me, as that is usually too way over the top to be much use,
but it does interest me because as you say, all of that happens before the
light hits the sensor.

I was wondering if perhaps the CMOS sensor's need to do some nearest
neighbour colour interpolation was perhaps partly offsetting the effect of
the polarizer.

I have to admit the difference is subtle, but compare the deep blue in the
top right corner of www.hortiphoto.com/pages/TRE0118.shtml with the mid-blue
of www.hortiphoto.com/pages2/TRE0230.shtml. Another shot
www.hortiphoto.com/pages2/SCH0017.shtml shows how the polarizer still works
well to increase contrast in what otherwise be a rather monochrome scene, so
I won't be ditching it just yet.

Geoff Bryant
www.hortiphoto.com


"Jim Townsend" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Geoff Bryant wrote:
>
> > After many years shooting transparency film I made the switch to digital
> > last August. I'm more than happy with the results but one thing

intrigues me
> > and perhaps someone here can enlighten me.
> >
> > Clearly cameras follow the same optical laws regardless of the capture
> > medium, but I've noticed that with digital filters seems to have less
> > effect.

>
> Are you using a circular polarizer ?? If so, you shouldn't see any
> difference. All the 'polarizing' is done before the light hits the film

or
> sensor.
>
> I have a 10D and use a polarizer now and then.. Just as Don Coon

indicates..
> They work fine on digicams..
>
>




 
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Jim Davis
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Posts: n/a
 
      01-03-2004
Try shooting at 90 degrees to the sun and rotate your filter for
maximum effect. This is how you will see the maximum effect. However,
different days, different effects. I have noticed a dramatic effect on
folliage, which is what I need the CP for, not making blue skies
darker. I can do that, any nurealistic blue skies which I like. If I
want more saturation, I crank up the saturation. Skies are usually
easy enough to mask as well.

I'm using Capture One and that really helps.

On Sat, 3 Jan 2004 13:19:53 +1300, "Geoff Bryant"
<(E-Mail Removed)> wrote/replied to:

>After many years shooting transparency film I made the switch to digital
>last August. I'm more than happy with the results but one thing intrigues me
>and perhaps someone here can enlighten me.
>
>Clearly cameras follow the same optical laws regardless of the capture
>medium, but I've noticed that with digital filters seems to have less
>effect.
>
>I can understand this with coloured filters that may be negated somewhat by
>automatic white balance, but what intrigues me is how the virtual trade mark
>effect of a polarizer - deep blue to almost black skies - seems so much
>reduced.
>
>Yesterday I took some test shots with my 10D. It's midsummer here in the
>southern hemisphere and the sky was clear blue with a just a very few pure
>white clouds. The polarized shots certainly showed sharper contrast between
>the clouds and the sky and the colours of the grass and other foliage were
>brighter because of the reduced reflection. However, the colour of the sky
>hardly changed; certainly not to the extent that I observed through the
>viewfinder. With film it would probably have gone the other way - a far
>greater effect.
>
>Is this really the case or am I missing something?
>
>Geoff Bryant
>www.hortiphoto.com
>
>
>


 
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Tony Spadaro
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Posts: n/a
 
      01-03-2004
Are your film shots mostly on slide film? If so do you tend to under-expose
for greater saturation, or use a high saturation film?
That's teh only difference I can think of.

--
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home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from my novel "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html
"Geoff Bryant" <(E-Mail Removed)> wrote in message
news:8OrJb.88$(E-Mail Removed)...
> Yes, I'm using a circular polarizer. And yes, it works. But although I

can
> see the effect, it doesn't seem nearly as extreme as with film, where the
> sky well above the horizon can become a really deep indigo blue. That
> doesn't worry me, as that is usually too way over the top to be much use,
> but it does interest me because as you say, all of that happens before the
> light hits the sensor.
>
> I was wondering if perhaps the CMOS sensor's need to do some nearest
> neighbour colour interpolation was perhaps partly offsetting the effect of
> the polarizer.
>
> I have to admit the difference is subtle, but compare the deep blue in the
> top right corner of www.hortiphoto.com/pages/TRE0118.shtml with the

mid-blue
> of www.hortiphoto.com/pages2/TRE0230.shtml. Another shot
> www.hortiphoto.com/pages2/SCH0017.shtml shows how the polarizer still

works
> well to increase contrast in what otherwise be a rather monochrome scene,

so
> I won't be ditching it just yet.
>
> Geoff Bryant
> www.hortiphoto.com
>
>
> "Jim Townsend" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
> > Geoff Bryant wrote:
> >
> > > After many years shooting transparency film I made the switch to

digital
> > > last August. I'm more than happy with the results but one thing

> intrigues me
> > > and perhaps someone here can enlighten me.
> > >
> > > Clearly cameras follow the same optical laws regardless of the capture
> > > medium, but I've noticed that with digital filters seems to have less
> > > effect.

> >
> > Are you using a circular polarizer ?? If so, you shouldn't see any
> > difference. All the 'polarizing' is done before the light hits the film

> or
> > sensor.
> >
> > I have a 10D and use a polarizer now and then.. Just as Don Coon

> indicates..
> > They work fine on digicams..
> >
> >

>
>
>



 
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Kevin McMurtrie
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Posts: n/a
 
      01-03-2004
In article <N_qJb.57$(E-Mail Removed)>,
"Geoff Bryant" <(E-Mail Removed)> wrote:

> After many years shooting transparency film I made the switch to digital
> last August. I'm more than happy with the results but one thing intrigues me
> and perhaps someone here can enlighten me.
>
> Clearly cameras follow the same optical laws regardless of the capture
> medium, but I've noticed that with digital filters seems to have less
> effect.
>
> I can understand this with coloured filters that may be negated somewhat by
> automatic white balance, but what intrigues me is how the virtual trade mark
> effect of a polarizer - deep blue to almost black skies - seems so much
> reduced.
>
> Yesterday I took some test shots with my 10D. It's midsummer here in the
> southern hemisphere and the sky was clear blue with a just a very few pure
> white clouds. The polarized shots certainly showed sharper contrast between
> the clouds and the sky and the colours of the grass and other foliage were
> brighter because of the reduced reflection. However, the colour of the sky
> hardly changed; certainly not to the extent that I observed through the
> viewfinder. With film it would probably have gone the other way - a far
> greater effect.
>
> Is this really the case or am I missing something?
>
> Geoff Bryant
> www.hortiphoto.com
>


A polarizer's effect is extremely dependent on the weather and the angle
of the sun. There are times when the sky is black 90 deg from the sun
and there are times when nothing happens at all. It all depends on
where the scattering of light happens and where the sun is relative to
your subject. Just a little bit of low altitude haze can completely
depolarize light from the sky.

You can try a fixed white balance just to make sure it's not a camera
issue but I'm guessing it was just a bad day for a polarizer.
 
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Dave Martindale
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Posts: n/a
 
      01-03-2004
"Geoff Bryant" <(E-Mail Removed)> writes:

>I can understand this with coloured filters that may be negated somewhat by
>automatic white balance, but what intrigues me is how the virtual trade mark
>effect of a polarizer - deep blue to almost black skies - seems so much
>reduced.


What happens if you disable the auto white balance, then shoot with and
without a polarizer?

Dave
 
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Skymuffins
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Posts: n/a
 
      01-03-2004

"Tony Spadaro" <(E-Mail Removed)> wrote in message
news:cYtJb.233234$(E-Mail Removed) r.com...
> Are your film shots mostly on slide film? If so do you tend to

under-expose
> for greater saturation, or use a high saturation film?
> That's teh only difference I can think of.


Polarizing filters are more effective when facing north. Perhaps your
shooting direction is different in these two shots?

- Harrison




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Jim Davis
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      01-04-2004
On 3 Jan 2004 21:31:58 GMT, http://www.velocityreviews.com/forums/(E-Mail Removed) (Dave Martindale)
wrote/replied to:

>
>What happens if you disable the auto white balance, then shoot with and
>without a polarizer?


polarized shots. no change in white balance

you should disable your auto white balance and shoot RAW at all times

you should get a good conversion program like Capture One

 
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