What I wrote applies not only to light metering but also auto-focus, as written
by Joachim.
The same reasoning applies: it’s just a matter of checking the result and
shooting again if needed.
Olaf
From: dh-photo-bounce@xxxxxxxxxxxxx [mailto:dh-photo-bounce@xxxxxxxxxxxxx] On
Behalf Of Olaf Marzocchi
Sent: Wednesday, December 02, 2015 11:03 AM
To: dh-photo@xxxxxxxxxxxxx
Subject: [dh-photo] Re: old skool stuff
I was aware of it, but new cameras with different sensors and focusing
technologies appeared since I bought my last polariser and I wonder if it those
rules still apply.
For example, mirrorless cameras with contrast-detect autofocus do not deviate
the incoming light with a mirror and they don’t have a phase detect chip. These
should be able to use the cheaper and brighter linear polarisers (about 1 stop
less light is blocked!).
http://www.dpreview.com/forums/thread/3538982
I wonder what would happen with the newest hybrid focusing systems that are
using phase detect on the sensor itself.
In any case, from what I understand the circular polariser only avoids problems
with light metering and this was important with film cameras: you had to wait
for the development to see the photo and a roll usually has only 12-36 shots.
Since digital cameras now have the preview, checking the photo after the shot
for correct exposure makes linear polarisers useful again: it is a matter of
correcting the exposure and shooting again if it happens that the camera got
the settings wrong.
Keeping this in mind, it should be possible save money by buying at a good
price linear polarisers in the second-hand market from people who “update”
them. Good polarisers can be expensive (see here for a comparison:
http://www.lenstip.com/139.1-article-Polarizing_filters_test_2015.html )
Olaf
From: dh-photo-bounce@xxxxxxxxxxxxx<mailto:dh-photo-bounce@xxxxxxxxxxxxx>
[mailto:dh-photo-bounce@xxxxxxxxxxxxx] On Behalf Of Joachim Seibert
Sent: Wednesday, December 02, 2015 12:43 AM
To: dh-photo@xxxxxxxxxxxxx<mailto:dh-photo@xxxxxxxxxxxxx>
Subject: [dh-photo] old skool stuff
Hi guys,
the last class (well, 2 1/2 classes actually) might have been a bit much. Sorry
for that!
Despite me using electronic cameras too, I am one of those film guys (i.e.
fossils).
Thinking all manual (focus, exposure etc.), I seemed to have overlooked the
problems introduced by automation. To me, a pol-filter just suddenly was not
available any longer... the same thing now was sold as a CPL (circular
polarizer). Since the thing was still analyzing linear polarization, this did
not make any sense to me (me thinking in film!).
Today, I learned something! It seems it is mandatory to convert the linear
polarization (which was fine for the century of film) into circular
polarization as to not confuse the sensors of the automated focus and exposure
determinations. Here is what Wikipedia has to say about this:
"For modern cameras, a circular polarizer is typically used; this comprises
firstly a linear polarizer which performs the artistic function just described,
followed by a quarter-wave plate which further filters the now-linearly
polarized light into circularly-polarised light before entering the camera.
This additional step avoids problems with auto-focus and light-metering sensors
within some cameras, which otherwise may not function reliably with a simple
linear polariser."
It seems, with technology moving on, problems are introduced which were unknown
in the past.
I learned even more: I definitely arrived in the stage of being a technological
fossil. Anyway, being what I am, a fossil, the fact that automation in modern
cameras keep having problems merely confirms my doubts about automation all
together.
Kind regards,
Joachim
