How many stops do I lose to a polariser?

On Feb 1, 1:42 pm, Ken Lucke <k....DeleteThis@glass-stones.com> wrote:

> Polarizers normally lose you 2-3 stops. Singh-Ray makes one that
> supposedly loses 2/3 [?] stop less than normal (they call it "LB" for
> "Lighter/Brighhter"), but I haven't tried it yet.
3 stops would be a lot of loss, 2 should be about the most you would
ever lose, a good one
should only lose about 1.5 stops. 1 stop would be the least a
polarizer could lose if it were perfect.


> Easy way to tell is to meter a scene, put the polarizer on and re-meter
> it.
Yup, this would tell you pretty quick, be sure to use a circular
polarizer as linear ones can
throw off the metering.
 >> Stay informed about: How many stops do I lose to a polariser? 

Ken Lucke wrote:
> In article <slrnes4qtg.i6h.justin.0701.DeleteThis@stigmata.purestblue.com>,
> Justin C <justin.0701.DeleteThis@purestblue.com> wrote:
>
>> Took some pictures the other day at Beachy Head. For those not
>> familiar, this is a large promontory on the south coast of England,
>> made up mainly of chalk (very much like the white cliffs of Dover).
>> It was a bright day, with very little cloud, and a low sun shining
>> directly on the cliff. The sky was a beautiful blue which contrasted
>> wonderfully with the cliff.
>>
>> When all around is chalk or sky metering is a bit of a headache! So I
>> pulled out an incident light meter. I also pulled out a polariser to
>> make the most of that blue sky, and make the most of it I did, I
>> rotated it and got the maximum dark blue. My question is this, how
>> many stops have I lost? I guessed two stops for the polariser,
>> adjusted my exposure accordingly, but, from the images, it doesn't
>> appear to have been enough.
>>
>> I've looked at the cases for my filters and there is no indication of
>> how much light they are cutting. I'm sure I remember having this on
>> my filter cases in the past, something like +1 or +2/3, to indicate
>> (to those not using TTL metering) that exposure compensation is
>> necessary.
>>
>> I look forward to your replies and comments on this.
>>
>> Justin.
>
> Polarizers normally lose you 2-3 stops. Singh-Ray makes one that
> supposedly loses 2/3 [?] stop less than normal (they call it "LB" for
> "Lighter/Brighhter"), but I haven't tried it yet.
>
> Easy way to tell is to meter a scene, put the polarizer on and
> re-meter it.

I will take some exception to that. If the polarizer is doing it's job,
the two images will not be the same subject. They both will have an overall
reduction, usually about 2 stops and parts of the polarized image will have
additional reduction to only parts of the image. The best exposure of the
second would likely not be the one metered assuming the original was
correct. It would depend on exactly what you wanted the filter to do.

Photography is an art and a science. This is one situation where the
art is in the drivers seat and not science.

--
Joseph Meehan

Dia 's Muire duit
 >> Stay informed about: How many stops do I lose to a polariser? 

Justin C wrote:

> When all around is chalk or sky metering is a bit of a headache! So I
> pulled out an incident light meter. I also pulled out a polariser to
> make the most of that blue sky, and make the most of it I did, I rotated
> it and got the maximum dark blue. My question is this, how many stops
> have I lost? I guessed two stops for the polariser, adjusted my exposure
> accordingly, but, from the images, it doesn't appear to have been enough.

This is rec.photo.digital. Chimp a little! Check the histogram on a
test exposure, and you'll know you're getting it right.

The filter factor varies between sources and between polarizers (and
linears seem to be different from circular), that I can find, but it
seems to be between 2 and 3.
 >> Stay informed about: How many stops do I lose to a polariser? 

Justin C wrote:
> Took some pictures the other day at Beachy Head. For those not familiar,
> this is a large promontory on the south coast of England, made up mainly
> of chalk (very much like the white cliffs of Dover). It was a bright
> day, with very little cloud, and a low sun shining directly on the
> cliff. The sky was a beautiful blue which contrasted wonderfully with
> the cliff.
>
> When all around is chalk or sky metering is a bit of a headache! So I
> pulled out an incident light meter. I also pulled out a polariser to
> make the most of that blue sky, and make the most of it I did, I rotated
> it and got the maximum dark blue. My question is this, how many stops
> have I lost? I guessed two stops for the polariser, adjusted my exposure
> accordingly, but, from the images, it doesn't appear to have been enough.
>
> I've looked at the cases for my filters and there is no indication of
> how much light they are cutting. I'm sure I remember having this on my
> filter cases in the past, something like +1 or +2/3, to indicate (to
> those not using TTL metering) that exposure compensation is necessary.
>
> I look forward to your replies and comments on this.
>
> Justin.
>

I depends on the scene and your position relative to the sun etc.
I would think that you would lose about 1.5 stops just for the polarizer
itself even if there was essentially no polarized light to be filtered.
If you are receiving a LOT of polarized light from the sky you might
lose another 1.5 stops.
Perhaps you could place the polarizer over the incident light meter's
sensor and adjust it for minimum and maximum effect.
That would give you the f-stop loss for the filter alone and for the
filter blocking polarized light.
Bob Williams
 >> Stay informed about: How many stops do I lose to a polariser? 

On Feb 1, 10:37 pm, Justin C <justin.0....DeleteThis@purestblue.com> wrote:
> Took some pictures the other day at Beachy Head. For those not familiar,
> this is a large promontory on the south coast of England, made up mainly
> of chalk (very much like the white cliffs of Dover). It was a bright
> day, with very little cloud, and a low sun shining directly on the
> cliff. The sky was a beautiful blue which contrasted wonderfully with
> the cliff.
>
> When all around is chalk or sky metering is a bit of a headache! So I
> pulled out an incident light meter. I also pulled out a polariser to
> make the most of that blue sky, and make the most of it I did, I rotated
> it and got the maximum dark blue. My question is this, how many stops
> have I lost? I guessed two stops for the polariser, adjusted my exposure
> accordingly, but, from the images, it doesn't appear to have been enough.
>
> I've looked at the cases for my filters and there is no indication of
> how much light they are cutting. I'm sure I remember having this on my
> filter cases in the past, something like +1 or +2/3, to indicate (to
> those not using TTL metering) that exposure compensation is necessary.
>
> I look forward to your replies and comments on this.
>
> Justin.
>
> --
> Justin C, by the sea.

yeah its usually 1.5 - 3 stops depending on how much light is
available etc..... bracketing would be the best idea
 >> Stay informed about: How many stops do I lose to a polariser? 

David Dyer-Bennet wrote:
> Justin C wrote:
>
>> When all around is chalk or sky metering is a bit of a headache! So I
>> pulled out an incident light meter. I also pulled out a polariser to
>> make the most of that blue sky, and make the most of it I did, I
>> rotated it and got the maximum dark blue. My question is this, how
>> many stops have I lost? I guessed two stops for the polariser,
>> adjusted my exposure accordingly, but, from the images, it doesn't
>> appear to have been enough.
>
> This is rec.photo.digital. Chimp a little! Check the histogram on a
> test exposure, and you'll know you're getting it right.

I disagree. A "proper" histogram does not mean the right exposure.
Only the resulting image can be the real test. If the results are right,
then the exposure is right.



>
> The filter factor varies between sources and between polarizers (and
> linears seem to be different from circular), that I can find, but it
> seems to be between 2 and 3.

--
Joseph Meehan

Dia 's Muire duit
 >> Stay informed about: How many stops do I lose to a polariser? 

"Justin C" <justin.0701 DeleteThis @purestblue.com> wrote in message
news:slrnes4qtg.i6h.justin.0701@stigmata.purestblue.com...
>
> Took some pictures the other day at Beachy Head. For those not familiar,
> this is a large promontory on the south coast of England, made up mainly
> of chalk (very much like the white cliffs of Dover). It was a bright
> day, with very little cloud, and a low sun shining directly on the
> cliff. The sky was a beautiful blue which contrasted wonderfully with
> the cliff.
>
> When all around is chalk or sky metering is a bit of a headache! So I
> pulled out an incident light meter. I also pulled out a polariser to
> make the most of that blue sky, and make the most of it I did, I rotated
> it and got the maximum dark blue. My question is this, how many stops
> have I lost? I guessed two stops for the polariser, adjusted my exposure
> accordingly, but, from the images, it doesn't appear to have been enough.
>
> I've looked at the cases for my filters and there is no indication of
> how much light they are cutting. I'm sure I remember having this on my
> filter cases in the past, something like +1 or +2/3, to indicate (to
> those not using TTL metering) that exposure compensation is necessary.
>
> I look forward to your replies and comments on this.
>
> Justin.
>
> --
> Justin C, by the sea.

Depends on the incoming polarization of the light. It could pass nearly all
the light or block it. If the light is not polarized (random) you lose
around 2 stops. Because in reality, a scene contains a mix, it is best to
bracket or as said, "chimp".

While we're at it, I was at a Meijers (sp?) store and found these circular
polarizers for $12 each in 52 and 58mm thread. These are "Targus" brand. My
local camera shop wants $35 for a "promaster", so I figured I have nothing
to lose (besides 24 bucks). I tested them out and they are polarizers and do
contain the 1/4 wave plate. They work well.

They don't come with any sort of case and claim to be "multi coated".
There's no coating I can see.
-S
 >> Stay informed about: How many stops do I lose to a polariser? 

Greetings Justin,

I believe you guessed correctly at the Polarizer. Actually, I believe it is
about 2.3 stops. But you likely did not account for the general brightness
of the scene, i.e. water white cliffs and blue sky. Kinda like a beach or
other bright scene. When in that situation it is wise to increase exposure a
bit to account for the unusual brightness. Again, about two stops if really
bright.

The meter in the camera will try to make the scene an 18% reflectance
instead of the bright scene that you saw. This happens on most general use
cameras.

The nice thing about digital, however, is that you can run a series of shots
to be sure you are getting the right image.

Talk to you soon,

Ron Baird
Eastman Kodak Company




"Justin C" <justin.0701.RemoveThis@purestblue.com> wrote in message
news:slrnes4qtg.i6h.justin.0701@stigmata.purestblue.com...
>
> Took some pictures the other day at Beachy Head. For those not familiar,
> this is a large promontory on the south coast of England, made up mainly
> of chalk (very much like the white cliffs of Dover). It was a bright
> day, with very little cloud, and a low sun shining directly on the
> cliff. The sky was a beautiful blue which contrasted wonderfully with
> the cliff.
>
> When all around is chalk or sky metering is a bit of a headache! So I
> pulled out an incident light meter. I also pulled out a polariser to
> make the most of that blue sky, and make the most of it I did, I rotated
> it and got the maximum dark blue. My question is this, how many stops
> have I lost? I guessed two stops for the polariser, adjusted my exposure
> accordingly, but, from the images, it doesn't appear to have been enough.
>
> I've looked at the cases for my filters and there is no indication of
> how much light they are cutting. I'm sure I remember having this on my
> filter cases in the past, something like +1 or +2/3, to indicate (to
> those not using TTL metering) that exposure compensation is necessary.
>
> I look forward to your replies and comments on this.
>
> Justin.
>
> --
> Justin C, by the sea.
 >> Stay informed about: How many stops do I lose to a polariser? 

On 2007-02-09, Ron Baird <ronbaird.DeleteThis@kodak.com> wrote:
> Greetings Justin,
>
Greetings to you too.

> I believe you guessed correctly at the Polarizer. Actually, I believe it is
> about 2.3 stops. But you likely did not account for the general brightness
> of the scene, i.e. water white cliffs and blue sky. Kinda like a beach or
> other bright scene. When in that situation it is wise to increase exposure a
> bit to account for the unusual brightness. Again, about two stops if really
> bright.

What part of "incident light reading" don't you understand?


> The meter in the camera will try to make the scene an 18% reflectance
> instead of the bright scene that you saw. This happens on most general use
> cameras.

What meter in what camera? I completely ignored it.


> Talk to you soon,

Hmmm.


> Ron Baird
> Eastman Kodak Company

They let you post to a newsgroup with their name attached? *And* you
breach netiqette by top posting! I'm sorry, but Kodak is losing
credibility with me by letting this out the door.

Justin.

--
Justin C, by the sea.
 >> Stay informed about: How many stops do I lose to a polariser? 

Justin C <justin.0701.DeleteThis@purestblue.com> wrote:
>With regard to the other follow-ups to my original, I think Ken Lucke
>hit the most simple solution. Though I am using an incident meter, using
>the camera's own meter with and without the polariser will show the
>difference which I can then apply to the reading from the incident
>meter. I shall keep this in mind for next time.

David Dyer-Bennet gave you the correct answer. Use the camera's
digital facilities to tell you what the exposure actually is.
By making sure the right side of the histogram approaches the
end of the graph you will guarantee maximum dynamic range
without blowing the highlights.

Of course, that assumes there are no highlights you don't mind
blowing, which there might actually be. If so, with a
blink-on-overexposure LCD display you can also determine exactly
what is overexposed, so that would perhaps be even better than
just the histogram. (As David mentioned, this is standard
procedure for beach scenes, snow scenes, or any example where
the average is not going to be about 18% grey.)

I agree with the basic idea of ignoring the light meter... except
that I'd add ignoring the external incident light meter too.

--
Floyd L. Davidson <http://www.apaflo.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd.DeleteThis@apaflo.com
 >> Stay informed about: How many stops do I lose to a polariser? 

Justin, in your original post you said:

"I look forward to your replies and comments on this"

yet you seem to have ignored them all except Ron - at whom
you hurl vitriol.

It doesn't matter to me, maybe it doesn't to you either, but
your attitude needs some work if you expect anyone to take
you seriously.

--
John Bean
 >> Stay informed about: How many stops do I lose to a polariser? 

On 2007-02-11, John Bean <waterfoot DeleteThis @gmail.com> wrote:
> Justin, in your original post you said:
>
> "I look forward to your replies and comments on this"
>
> yet you seem to have ignored them all except Ron - at whom
> you hurl vitriol.

I didn't ignore them. It is unfortunate that retention on my news-server
is such that they have expired (I've been away since last Saturday at a
trade show) and spent much of the prior week preparing. I've caught up
with them on Google but I'm not signing up to Google to post replies,
I'll tack them on the end here.

I think "vitriol" is rather strong. Ron purports to post from Kodak, a
highly respected company in the photography industry, one without which
the whole industry would be in very different shape. It was they who
opened it up to the masses and I am grateful for that - I still have a
Kodak Retina camera, which I love dearly but, alas don't use due to the
processing costs. When posting from such an august position one should
take the utmost care in what one writes, I doubt any advert ever leaves
the company without very much scrutiny, of the facts, details, and
comparison with corporate image documents; yet Ron posted a message
which missed the point, and was poorly presented, not useing established
usenet posting style - editing the original and inserting his post after
the relevant part of the original. If Kodak is accepting of this
slap-dash approach it tells me that their standards are not high enough
to hold them in the high regard I have done any longer.


> It doesn't matter to me, maybe it doesn't to you either, but
> your attitude needs some work if you expect anyone to take
> you seriously.

People do take me seriously, just not here.


With regard to the other follow-ups to my original, I think Ken Lucke
hit the most simple solution. Though I am using an incident meter, using
the camera's own meter with and without the polariser will show the
difference which I can then apply to the reading from the incident
meter. I shall keep this in mind for next time.

Scott W, fortunately mine is a circular polariser. I bought it some
years ago for an EOS, I recall reading that linear polarisers caused
problems with the autofocus method used at that time.

Thanks to those others who also replied, some interesting points were
raised. I now know how to deal with this situation when it arises again
- as it will, I enjoy the walk around Beachy Head and shall be there
again before long.

Justin.

--
Justin C, by the sea.
 >> Stay informed about: How many stops do I lose to a polariser? 

On 2007-02-11, Floyd L. Davidson <floyd.TakeThisOut@apaflo.com> wrote:
> Justin C <justin.0701.TakeThisOut@purestblue.com> wrote:
>>With regard to the other follow-ups to my original, I think Ken Lucke
>>hit the most simple solution. Though I am using an incident meter, using
>>the camera's own meter with and without the polariser will show the
>>difference which I can then apply to the reading from the incident
>>meter. I shall keep this in mind for next time.
>
> David Dyer-Bennet gave you the correct answer. Use the camera's
> digital facilities to tell you what the exposure actually is.
> By making sure the right side of the histogram approaches the
> end of the graph you will guarantee maximum dynamic range
> without blowing the highlights.
>
> Of course, that assumes there are no highlights you don't mind
> blowing, which there might actually be. If so, with a
> blink-on-overexposure LCD display you can also determine exactly
> what is overexposed, so that would perhaps be even better than
> just the histogram. (As David mentioned, this is standard
> procedure for beach scenes, snow scenes, or any example where
> the average is not going to be about 18% grey.)
>
> I agree with the basic idea of ignoring the light meter... except
> that I'd add ignoring the external incident light meter too.

I can see your point. Noted for future reference.

Justin.

--
Justin C, by the sea.
 >> Stay informed about: How many stops do I lose to a polariser?