Hi everyone!
I have been following your discussions for some while now with great
interest, and now that I have an TL120 on my own I would once more
like to ask a question. I really hope this matter has not been
discussed too often.
I would like to use polarized filters for my camera as I used to do
with my analogue and later digital SLR. What I would like to know is
firstly how I can "synchronize" the two filters so that I achieve the
same effect for both lenses, and secondly how I can then find out the
respective filter factor. Would I need a third filter or put one of
the two filters on the upper lense? I work mainly with an external
digital light meter and simply do not know how to accomodate its
results for the polarized filters.
I am very much looking forward to some hints,
Regards,
Andreas / Germany

--- In MF3D-group@yahoogroups.com, "autre_valse"
wrote:
Would I need a third filter or put one of

> the two filters on the upper lense? I work mainly with an external
> digital light meter and simply do not know how to accomodate its
> results for the polarized filters.
> I am very much looking forward to some hints,
> Regards,
> Andreas / Germany
>

Hi Andreas, I also have used polarizers with the TL120. My technique
is to use 3 filters, obviously rotating the viewer filter to desired
effect then rotating the marker line on the other 2 filters to the
same angle`. These marker lines have to be checked for alignment, but
they are usually well calibrated. To do this, set one of the three
filters standing with light coming through it, then looking through
filters, check that the other two filters completely block the light
at the same rotation angle as per the marker. This should be at 90
degrees to the first filter. I hope this is clear! As far as the
exposure compensation goes, they can vary a little between brands and
grades. Best is to measure a scene with lightmeter, the again with
the filter in front of it rotated to the desired effect angle. This
will give you a constant compensation value. Also note that you don't
need to buy the expensive Circular Polarizers, only the cheaper
linear ones. The circulars are only needed on digital and video
because of the plastics used in their sensors. Hope this is of value
to you. Happy MF3Ding :) Peter

autre_valse wrote:

> I would like to use polarized filters for my camera as I
> used to do with my analogue and later digital SLR. What I
> would like to know is firstly how I can "synchronize" the
> two filters so that I achieve the same effect for both
> lenses, and secondly how I can then find out the
> respective filter factor. Would I need a third filter or
> put one of the two filters on the upper lense? I work
> mainly with an external digital light meter and simply do
> not know how to accomodate its results for the polarized
> filters.

There isn't really a requirement to install a polarizer on
the viewing lens unless you are planning on using the
internal meter. It will make it easier to determine the
effect of the filter on your image, but it isn't a
requirement. I will, most often, compose an image with the
viewfinder, but orient my polarizer with a filter held in
front of my eye and transfer that to my camera.

I have a 4-inch square of polarizing material for use with my
TL-120. I can view the scene and meter through it, then hold
it in front of my lenses when I trip the shutter. With this
method, the two lenses' filters are always aligned. It does
mean, however, that I have to be very careful to avoid
unwanted reflections and flare.

You can also just screw a filter on each of the lenses and
rotate them independently. The trick is having them set the
same (synchronized) when you trip the shutter. For this, you
need an index mark on each filter. When the indexes are in
the same relative location, your filters will be oriented the
same.

If your filters are not indexed, you can do so yourself.
Place one in front of the other and look through them while
rotating one. When the image is darkest, the planes of
polarization are at right angles to each other. When it
brightest, the planes are parallel. When you have the
brightest image, mark the edges of your filters.
________________________________________
John Thurston
Juneau, Alaska
http://stereo.thurstons.us

Thanks John & Peter, that was most enlightening!
Andreas

--- In MF3D-group@yahoogroups.com, John Thurston wrote:
>
> autre_valse wrote:
>
> > I would like to use polarized filters for my camera as I
> > used to do with my analogue and later digital SLR. What I
> > would like to know is firstly how I can "synchronize" the
> > two filters so that I achieve the same effect for both
> > lenses, and secondly how I can then find out the
> > respective filter factor. Would I need a third filter or
> > put one of the two filters on the upper lense? I work
> > mainly with an external digital light meter and simply do
> > not know how to accomodate its results for the polarized
> > filters.
>
> There isn't really a requirement to install a polarizer on
> the viewing lens unless you are planning on using the
> internal meter. It will make it easier to determine the
> effect of the filter on your image, but it isn't a
> requirement. I will, most often, compose an image with the
> viewfinder, but orient my polarizer with a filter held in
> front of my eye and transfer that to my camera.
>
> I have a 4-inch square of polarizing material for use with my
> TL-120. I can view the scene and meter through it, then hold
> it in front of my lenses when I trip the shutter. With this
> method, the two lenses' filters are always aligned. It does
> mean, however, that I have to be very careful to avoid
> unwanted reflections and flare.
>
> You can also just screw a filter on each of the lenses and
> rotate them independently. The trick is having them set the
> same (synchronized) when you trip the shutter. For this, you
> need an index mark on each filter. When the indexes are in
> the same relative location, your filters will be oriented the
> same.
>
> If your filters are not indexed, you can do so yourself.
> Place one in front of the other and look through them while
> rotating one. When the image is darkest, the planes of
> polarization are at right angles to each other. When it
> brightest, the planes are parallel. When you have the
> brightest image, mark the edges of your filters.
> ________________________________________
> John Thurston
> Juneau, Alaska
> http://stereo.thurstons.us
>

If you use polarizing filters as often as I do (they are essential for landscape photographers) you might want to rig your TL120 like I did my Sputnik and Stereflektoskop.  To each of my cameras I attached a bracket with two prongs.  I cut polarizing material I bought from Edmund Scientific to 4 inch (100mm) diameter and mounted it in a ring with an internal lip that allows it to snap onto the prongs and rotate freely.  The bracket holds the surface of the filter perpendicularly about 1mm in front of the lenses so ir does not get scratched and there is no reflection problem from the rear.

Oleg Vorobyoff

John Thurston wrote:

> I have a 4-inch square of polarizing material for use with my
> TL-120. I can view the scene and meter through it, then hold
> it in front of my lenses when I trip the shutter. With this
> method, the two lenses' filters are always aligned. It does
> mean, however, that I have to be very careful to avoid
> unwanted reflections and flare.

Dear Oleg! Could you show this design in a picture? Would be great! Kind regards, Chris
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