A70 with pola-filter?

[RobertJ]

I wonder if it's possible to fit a pola filter on my A70?
Should I use a lensadapter LA-DC52C with a 52 mm (circulair) pola-filter? Can you turn the filter then?

Which combinations are in use?

Regards,
Robert

[Spirit]

Funny you should ask this. For the last 30 minutes or so I've been doing an online search about this very subject.

[RobertJ]

So I did, but no solutions so far.

[GoldenOlive]

RJ
I have recently aquired the LA-DC52C adapter & can attach a Cokin 'Circular Pola 52"
This is the 52mm circular polariser.
You can rotate it [Its basically a 2 piece item - thread & rotating element with lens, in 1 unit]
I shot a series of 4 pics of the same scene across a harbour, rotating the filter 90 degrees between each shot.
I could not discern any difference between them, so scratching my head over the circular feature/ what it is meant to do.
I could have purchased a 'pola' filter [non rotating], but for some reason went for the circular.
What the filter is good for is cutting down reflected glare off water & deepening the blue of the sky.
Those aspects were noticeably improved over test shots without the filter.
GO

[stopbath]

Cirular polarizer and linear polarizers work in differing ways to achieve more or less the same thing.

The linear polarizer will block out light that is orintated in one direction. This is the filter that you would use in manual focus cameras. As you turn the filter, (there should be a white dot or some other indicator to show the orientation of the filter) light will be blocked from that direction. You will see the difference as you turn it. Reflections in the window will suddenly go away, and come back as you continue turning the filter.

The circular filter need not be turned. It is used for Auto Focus cameras as the AF mechanism can't function well with with linear filters. These filters will block the light orientated from the center to the outside. So, the top of the picture will block light orientated to the top, left left, right right, and so on. Turning the filter will have no effect.

I have never done any comparisons between the two.

You can use a linear on an AF camera, but when the filter is blocking light from the top (usual orientation) the AF will likely not be able to figure the distance to the subject. You could then use manual focus without any problem though.

Why a circular polarizer was turnable, I don't know. The turning function is required for the linear, but not for the circular. Perhaps you got a linear instead?
Happy polarizing.

[Spirit]

GO

Any chance you could post a few with and without pictures?

[RobertJ]

I don't no if we understand eachother.

Both lineair and circular pola-filters are turnable and must be turnable.

With the sun in your back, a blue sky with white coulds you must be able to see the difference when you turn the pola-filter. The contrast between the bleu sky and cloud will differ. The polarizing effect depends on the angel with the sun.

When you see the maximum effect turn yourself 360 degrees and see the difference.

I held the circulair pola-filter which I use on my eos 30 in front of the lens of the A70 (turning between my finger and thumb) and it worked. But this is a clumsy way of working.

Now I know that the combination with the filter adapter will work, thanks!

Best regards,
Robert

[stopbath]

You are right about the circular being moveable, I had an incorrect idea on how they worked. Now I know: both linear and circular both polarize in the same way, but the circular has an additional layer behind the polarizer layer that mixes up the light orientation again so that the AF and meter work correctly.

Here is a good link on the difference between linear and circular:

http://www.geocities.com/cokinfiltersystem/polarizer.htm

[RobertJ]

A very helpful site!
I used my eos 30 with pola at my hollydays last week in Norway. Next week I will see the photografic results!

Best regards,
Robert

[Heimdall]

Hi
Just so I dont buz the false filer: So I have to get a Circular polarizer for my A70?
Just got my Alu-Lense adapter (19 euro) today!!

Heimdall

[KevinG]

Does the polarizer have to be in front of the lens system to effectively reduce glare?

I almost picked up a 52mm circular polarizer the other day, but didn't... many of the shots I take outside (landscape, wildlife) are with the tele lens in place. The filter I saw had front threads, so it could be used between the la-dc52 and the tc-dc52, but I don't know if it will work properly there.

Kevin

[KevinG]

Heimdall wrote:
Hi
Just so I dont buz the false filer: So I have to get a Circular polarizer for my A70?
Just got my Alu-Lense adapter (19 euro) today!!

Heimdall




It doesn't seem to be necessary... according to the article that stopbath posted (see previous link) linear or cicular makes no difference to a digital camera because they don't use a beam-splitting meter the way an SLR does.

According to the article, it makes no difference to the AF mechanism in any case, but it can mess up the metering system in an SLR. In the digital camera, the light is metered by the circuitry inside the camera based upon the intensity of the light falling upon the CCD... so either should work fine.

Quote: . Digital cameras in general do not have reflection mirrors, and, as a result, can use both (linear or circular) polarizers.

[Heimdall]

OK! thanks!

..and off I go for a pol filter!

Heimdall