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Circular polarizer
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PostPosted: Fri Jan 09, 2009 4:13 pm    Post subject: Circular polarizer Reply with quote
Today I used B+W CP filter at first time, sky was blue , but I would more deep blue I did rotate filter almost around the clock , but I didn't see any changes. Is it normal ? Or I bought a fake filter ?


PostPosted: Fri Jan 09, 2009 4:17 pm    Post subject: Reply with quote
PL filters work only if you take pictures perpendiculary to sun (the sun must be on your left or on your right).

The effect doesn't look as good on LCD or viewfinder, as on the final picture. You can try - turn it 1/8, tak picture, turn it again by 1/8... etc. and than compare these pictures.


PostPosted: Fri Jan 09, 2009 4:23 pm    Post subject: Re: Circular polarizer Reply with quote
Attila wrote:
Today I used B+W CP filter at first time, sky was blue , but I would more deep blue I did rotate filter almost around the clock , but I didn't see any changes. Is it normal ? Or I bought a fake filter ?

Taken from http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/filter/polarizer.html :

One of the best-known use of polarizers is darkening blue sky. However, not all part of the sky can be darkened. A simple rule goes as follows (see the image below). Point your index finger at the sun and extend your thumb at a 90 angle to your index finger. Pointing your lens in the direction of your thumb will achieve the maximum effect.


PostPosted: Fri Jan 09, 2009 4:58 pm    Post subject: Reply with quote
Many thanks!!


PostPosted: Fri Jan 09, 2009 5:46 pm    Post subject: Reply with quote
just for fun:

my old comparision: Singh-Ray LB Color-Combo polarizer (left) vs. Hoya WARM C-PL (right):






And illustration of different speed of different polarising filters (the upper - cheap OEC linear polarizer is twice as fast as the bottom warming CP-L filters (Singh-Ray and Hoya), but its polarisating power is not lower):



PostPosted: Fri Jan 09, 2009 10:35 pm    Post subject: Reply with quote
Thank you! I met first time a cheap Korean one , this filter damaged lens IQ fully I did throw out. Now I have B+W and today I didn't see difference, I hope I will sometimes later.


PostPosted: Fri Jan 09, 2009 11:11 pm    Post subject: Reply with quote
Hello,

Attila you can also check your filter taking a picture of a glass object (kind of a sphere or a bottle) reflecting something: turning the filter you should be able to wipe out the reflections ... Or you can simply check your exposure meter: the strongest polarizing effect should be reached when the light measurement is about 2 f/stops slower ... I bought two B+W PL from an HK-based seller, and got great results wrt. my (now sold) Hoya PL ...

Best regards


PostPosted: Fri Jan 09, 2009 11:24 pm    Post subject: Reply with quote
Many thanks for great tip!


PostPosted: Sat Jan 10, 2009 9:23 am    Post subject: Reply with quote
You could also test it on LCD - if you look through the filter in right direction (filter thread directed to you) and turn it round, the image on LCD will disappear.

Here is a nice video showing some possibilities of C-PL filter, so you can see the results:

http://www.youtube.com/watch?v=0Lia2cF72hY&fmt=6


PostPosted: Fri Jan 16, 2009 11:56 pm    Post subject: Reply with quote
I expect there are better methods for it, but I have always just turned the filter until the sky is as dark as the filter allows. Also, I simply make sure the sun is somewhere behind the end of the lens barrel, whether truly behind me or just to one side. These steps have nearly always provided satisfactory results.


PostPosted: Sat Jan 17, 2009 12:48 am    Post subject: Re: Circular polarizer Reply with quote
Attila wrote:
Today I used B+W CP filter at first time, sky was blue , but I would more deep blue I did rotate filter almost around the clock , but I didn't see any changes. Is it normal ? Or I bought a fake filter ?


I have a couple of friends who can never see the difference in their viewfinder, even when I line it up for them.
I am thinking it may be to do with some peoples eyesight?
I should add that as far as I know the guys do have normal eyesight and are also fairly experienced photographers.
I have 4 polarising filters one is just a plastic Cokin one and I see a huge difference when I turn any of them but I repeat my couple of mates don't see a thing?
We have often had a good laugh over it!


PostPosted: Sat Jan 17, 2009 12:59 am    Post subject: Reply with quote
Might be this is a problem for my eye too, I did see really nothing. Perhaps in better wheather I will see.


PostPosted: Sat Jan 17, 2009 2:37 pm    Post subject: Reply with quote
As all know, the filters (all of them) reduce the definiton and the contrast of the lens . I prove it by myself. And the pol is a double filter - with two cristals-, perhaps with double effects too.

My test said: With hexanon 50/2 and XP2-at 400 iso-

Without filter : 90 pairs of l/mm

With B&W UV filter : 70 pairs of l/mm.

I saw with 60X microscope.

Is better the Post Prod correction? I don't know this.

The best for you, friend Attila.

Rino.


PostPosted: Sat Jan 17, 2009 2:46 pm    Post subject: Reply with quote
I never use any filter about this reason what you say Rino, but polarizer can be life saver in some situation.


PostPosted: Sat Jan 17, 2009 7:10 pm    Post subject: Reply with quote
estudleon wrote:
As all know, the filters (all of them) reduce the definiton and the contrast of the lens . I prove it by myself. And the pol is a double filter - with two cristals-, perhaps with double effects too.

My test said: With hexanon 50/2 and XP2-at 400 iso-

Without filter : 90 pairs of l/mm

With B&W UV filter : 70 pairs of l/mm.

I saw with 60X microscope.

Is better the Post Prod correction? I don't know this.

The best for you, friend Attila.

Rino.


If you try to shot landscapes without a polarizer and a ND split screen I will stare in marvel looking at your 90 lpm overexposed skies or underexposed terrains that will put a shame on pro landacapes shooters 70 lpm shots with perfect exposition all over the frame.

You know, shots need to be admired with a microscope Wink

Sorry for being ironic, but really, this "lpm - MTF - whatever other microdevice misuration" has nothing to do with photography.

Btw, if someone of you really care for lpms, throw away the 35mm junk and use medium or large format for landscape shooting. 35 mm isn't simply the right instrument.


PostPosted: Sat Jan 17, 2009 7:31 pm    Post subject: Reply with quote
A G Photography wrote:
estudleon wrote:
As all know, the filters (all of them) reduce the definiton and the contrast of the lens . I prove it by myself. And the pol is a double filter - with two cristals-, perhaps with double effects too.

My test said: With hexanon 50/2 and XP2-at 400 iso-

Without filter : 90 pairs of l/mm

With B&W UV filter : 70 pairs of l/mm.

I saw with 60X microscope.

Is better the Post Prod correction? I don't know this.

The best for you, friend Attila.

Rino.


If you try to shot landscapes without a polarizer and a ND split screen I will stare in marvel looking at your 90 lpm overexposed skies or underexposed terrains that will put a shame on pro landacapes shooters 70 lpm shots with perfect exposition all over the frame.

You know, shots need to be admired with a microscope Wink

Sorry for being ironic, but really, this "lpm - MTF - whatever other microdevice misuration" has nothing to do with photography.

Btw, if someone of you really care for lpms, throw away the 35mm junk and use medium or large format for landscape shooting. 35 mm isn't simply the right instrument.


Touche.

Pardon. I dared to do what it pleases to me without your approval. Moan the happened thing. I will put more care the next time.

It did not affect your irony to me, although it would have preferred a subtility, but each does that one so it is enabled.

Thanks. Rino.


PostPosted: Sat Jan 17, 2009 7:37 pm    Post subject: Reply with quote
I omitted to think of the photographic aspect because now I can understand why my skies appera oversposed in 40 years taken pics).

It never is behind schedule for learning to photograph skies.

Rino.


PostPosted: Sat Jan 17, 2009 7:46 pm    Post subject: Reply with quote
I am very ashamed. Now I see that all the photographies of Bresson-Cartier are false. They altered skies to them since he did not use filter pol. Wow, of the things that one comes to find out.

Rino


PostPosted: Sat Jan 17, 2009 7:53 pm    Post subject: Reply with quote
I'm sorry you took my ironic remarks this way, but I still think HCB never tested his shots lpms under a microscope to decide which lens to use.


PostPosted: Sat Jan 17, 2009 7:59 pm    Post subject: Reply with quote
A G Photography wrote:
I'm sorry you took my ironic remarks this way, but I still think HCB never tested his shots lpms under a microscope to decide which lens to use.


But I do. And I happy with this and no need that nobody say OK or not, like I don't be ironic with the members of the forum.

Perhaps you have the reason, but .........

Regards, Rino.


PostPosted: Sat Jan 17, 2009 8:12 pm    Post subject: Reply with quote
Once the bitching has subsided, let's get back to the original question...

Many post seventies SLRs (and every AF SLR) contain beam-splitting mirrors or prisms, which act as polarizers. That is the very reason that they require a "circular" polarizer, but it also reduces or obliterates the in-finder effect of any polarizer. If you need full visual control, you are better off with a older SLR that can still do with linear polarizers.


PostPosted: Sat Jan 17, 2009 8:21 pm    Post subject: Reply with quote
Rino, probably this is the problem with internet, it lacks a lot of non verbal communications (gestures, smiles, etc). I was really laughing when I wrote my first comment and if we would have been sitting one in front of the other you'd probably would have tell me "f**k you" and laugh together with me.

I was ironic simply because if you want to give information on why and how use a circular polarizer or not lpms should not enter in the equation.

If definition is paramount in a shot there are appropriate instruments that gives all the definition you can need and even beyond.

Then one can shot with an old triplet of the '20 or with a 8x10 view camera, it depends which results want to achieve. I could care less.

Still in landscape shooting ND split screens and polarizers are essential instruments because you have to bring the dynamic range of the scene into the more limited dynamic range of the film, especially if we're talking about slides and digital.

There's no discussion about it unless one loves black shadows or blown out skies.

Anyway to bring the thread on a more technical discussion I just posted an example image shot on Velvia 50 with a very cheap lens (Meyer Lydith) and then scanned and post produced at Canon 5D (Mark I) resolution so to compare.

Be careful, the image is HUGE.

http://forum.mflenses.com/velvia-50-in-35mm-t13981.html#118157


PostPosted: Sat Jan 17, 2009 8:35 pm    Post subject: Reply with quote
Sevo wrote:
Once the bitching has subsided, let's get back to the original question...

Many post seventies SLRs (and every AF SLR) contain beam-splitting mirrors or prisms, which act as polarizers. That is the very reason that they require a "circular" polarizer, but it also reduces or obliterates the in-finder effect of any polarizer. If you need full visual control, you are better off with a older SLR that can still do with linear polarizers.


My Canon 5D works perfectly well with a circular polariser and I can see the effect through the viewfinder, no problem. I would expect it to be obvious in skies (at right angles to the sun), looking at sparkling water or looking at reflections in windows.

If you really want top quality, you have to take care not to overdo the polarisation of blue skies. At the correct angle, a polariser can turn them almost black and (in digital) trying to pull the blue back up again results in horrible chromatic noise.

I can't remember if a polariser produces any effect at all in skies taken when the sun is directly overhead, I suspect it won't because the light will be equally polarised in all directions. If you took your pictures at noon you may not have given the filter a chance (though at this time of year the sun is probably low for you anyway).


PostPosted: Sat Jan 17, 2009 8:37 pm    Post subject: Reply with quote
A G Photography wrote:
Rino, probably this is the problem with internet, it lacks a lot of non verbal communications (gestures, smiles, etc). I was really laughing when I wrote my first comment and if we would have been sitting one in front of the other you'd probably would have tell me "f**k you" and laugh together with me.

I was ironic simply because if you want to give information on why and how use a circular polarizer or not lpms should not enter in the equation.

If definition is paramount in a shot there are appropriate instruments that gives all the definition you can need and even beyond.

Then one can shot with an old triplet of the '20 or with a 8x10 view camera, it depends which results want to achieve. I could care less.

Still in landscape shooting ND split screens and polarizers are essential instruments because you have to bring the dynamic range of the scene into the more limited dynamic range of the film, especially if we're talking about slides and digital.

There's no discussion about it unless one loves black shadows or blown out skies.

Anyway to bring the thread on a more technical discussion I just posted an example image shot on Velvia 50 with a very cheap lens (Meyer Lydith) and then scanned and post produced at Canon 5D (Mark I) resolution so to compare.

Be careful, the image is HUGE.

http://forum.mflenses.com/velvia-50-in-35mm-t13981.html#118157


Itself having the conception of positivar the negative in 40 xs 50 or 30 x 40. For it an average of near 90 l/mm or more is required in the negative of 35mm.
If we used a negative of 4x5 or 8x10 it is another thing.
And the polarizer, unquestionably useful, continues being two crystal pieces the front of the objective with the consequences already said.
If we want to maintain the image in the monitor or to make copies smaller, is all OK with pol and others filters of effects.
I did not clarify that the question, for my, is the size of the copy since whenever volume I do it to photos with that purpose like objective.
And as far as the communication, I also request my excuses. Under no concept I have wanted to offend neither nor no member of the forum.
Regards, Rino


PostPosted: Sat Jan 17, 2009 8:40 pm    Post subject: Reply with quote
PaulC wrote:
I can't remember if a polariser produces any effect at all in skies taken when the sun is directly overhead, I suspect it won't because the light will be equally polarised in all directions.


Yep, very limited effect that doesn't worth the effect.
You have to rely on the ND split filters in those occasions (using a darker one than with the polarizer), even if shooting at noon with the sun overhead isn't the best practice anyway.
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