Questions: different filter polarizer plannar-circular
E. Tjawi
I have few question:
Is it really gonna make a big different if I used the circ pol filter
compare to if I just use the plannar one? (My lense in internal ring - AF)
What would be the different between expensive (=good?) cric pol filter and
the cheap (=not so good?) one? I went to some store and pick up some plannar
one. By looking at some glass window, I realize that the reflection is gone
at some certain angle; however, when I pick up the circular polarizer
filter, no matter how much rotation I did, the reflection on the glass
window did not diminish at all.
Can somebody explain these?
Thank you.. and Go Nikon!
:)
E. Tjawi
Al Denelsbeck
the autofocus and metering systems of most of today's SLR cameras. Autofocus
and metering is often accomplished through a half-silvered portion of the
mirror, usually reflecting the incoming light by another mirror behind the
main one. This will polarize the incoming light. A linear polarizer might be
aligned in such a way as to reduce this reflected light too much, further
than the overall affect of the polarizing filter, and will fool the camera's
metering system into setting the wrong exposure, or simply prevent the
autofocus from working at all.
A circular polarizer has the ability to prevent this, from moving the
polarized light waves partially out of 'step', I believe by a quarter-cycle.
I don't pretend to know why this works, but it does. Basically, if your
camera manufacturer recommends a circular polarizer, use one.
Differences in prices between any two filters of the same type or color
usually comes from the type of glass used, accuracy of color, and low
distortion. It may also come from a manufacturer putting the word 'Pro' on
their product and nothing more.
Finally, with a circular polarizer, no effect will be noticed unless you are
looking through it the same way that it would be on the camera, threads
towards your eye. If it's backwards, it doesn't work.
Go Photography! - Al.
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E. Tjawi wrote in message
<8aYm6.23665$t26.7...@typhoon.mw.mediaone.net>...
F. J. Roy
reflections you have to be approx 30 degrees off the reflecting surface for the
best results.
Francis in VT
Husband and Wife
>or simply prevent the autofocus from working at all.
On my old Minolta 7000i, the wrong polarizer will make the lens focus back and forth continuously.
Dave
E. Tjawi
Hass anybody compare the picture quality between expensive (good?) Circh Pol
Filter and some cheap (not so good?) ones? Any web site samples?
Please let me know. I just got some lens that have 77mm dia, and try to
decide how much more money to spend on filters.
E. Tjawi
F90S
20-35 Tokina 3.5
35-70 Nikon 3.3-4.5
80-200 Nikon ED 2.8
SB-28
James R Dees
A circular has an additional quarter-wave plate or scrambler behind
the (still linear) polarizing foil. Although not scientifically
correct, it more or less restores the natural 50/50 vertical/horizontal
balance of polarization, without affecting the initial pictorial result.
Only by restoring this natural balance it will allow the light
metering and AF sensors to work properly, as they use polarizing beam
splitters. With a linear filter, you would risk a cross-polarizing
effect, ie a black-out. Bad for both light metering and AF.
In spite of what most people will tell you: the main reason to buy a
circular polarizer is *not* the AF sensor, but the light metering
system. You can *see* when AF goes haywire (it won't shift focus, it
just has more difficulty to lock on), but you can only guess what
happens with your light meter!
Actually, the first circulars were required long before AF existed,
and are still required for non-AF cameras today (Rollei 600x series
is a nice example).
E. Tjawi <etjawinoto@.remove.wi.rr.com> wrote in message
news:8aYm6.23665$t26.7...@typhoon.mw.mediaone.net...
Murph
I've been using a cheap one from Porters and have no complaints