How many stops do I lose to a polariser?

On 2007-02-09, Ron Baird 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.

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

On 2007-02-11, John Bean 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.

Justin C 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)

On 2007-02-11, Floyd L. Davidson wrote:
Justin C 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.