Circular polarizers

Scottsmadness

Just need some input about circular polarizer filters. I see such a wide range of prices on these things on ebay. Some are $20 bucks, some are $120 bucks. Are they not doing the same thing? You know the old adage: "You get what you pay for" and I am sure that this applies here also. Just hoping someone will come a long and say: "yeah...............the cheap one work just as well." Wishfull thinking? :dunno

David_S85

And they can run much more than that.

You can pick up some fact vs. fiction about these (as well as perhaps buy some) at http://www.2filters.com or at http://www.camerafilters.com

Neither of those websites are designed well, and digging up resources at either can be maddening. But it's there, somewhere. Disclaimer: I have bought from both these businesses, but am not connected to either of them other than being their customer.

Quality is important if you are graduating to the better lenses and higher end cameras. With the quality comes better physical design, clearer optical glass, more consistant application of coatings, as well as multi-spectral coatings.

It would make no sense whatsoever to do critical shooting with $1,000+ lenses and then apply a $20 filter.

You no doubt know this, but for the benefit of others visiting this post: SLR's need circular polarizers, due to the phase detection type of autofocus. Common digicams can use either circular or linear polarizers with their contrast detection autofocus systems.

Scottsmadness wrote:

Just need some input about circular polarizer filters. I see such a wide range of prices on these things on ebay. Some are $20 bucks, some are $120 bucks. Are they not doing the same thing? You know the old adage: "You get what you pay for" and I am sure that this applies here also. Just hoping someone will come a long and say: "yeah...............the cheap one work just as well." Wishfull thinking?

ian408

What David says about quality is important. Also important is what sort of
lens you're working with. If it's a wide angle, like the Canon 10-22, then
consider a thin filter. This helps prevent vignetting on the wider range.

David_S85

What Ian says about thin filters on wides is important. However, if you are using a polarizer on a super-wide angle, besides the vignetting issue (and there will be vignetting at the widest, no matter what), the consistancy of a sky rendered by a polarizer will be kinda odd. It will catch only part of the sky making some of it darker and leaving another large area lighter. This is due mostly to how polarizers work - they only affect the areas at right angles from the sun, relative to your position. In short, avoid the use of polarizers for skies with wides.

The use of a polarizer for wides should be limited to reduction of glare on glass windows, or glare on water from the sun, or other such things.

Nikolai

I agree

David_S85 wrote:

... avoid the use of polarizers for skies with wides...

With a super wide glass it's way better to take bracketed shot (or simply develop underexposed RAW) and then use any standard blending technique to get a nice deep blue sky from there..

gluwater

In case you don't believe anyone above about the weirdness of a Circular Polerizer with an ultra wide, here is an example.
20D
Canon 10-22
Tiffen Wide Angle Circular Polerizer (made specifically for Wide Angle)

Scott_Quier

David_S85 wrote:

This is due mostly to how polarizers work - they only affect the areas at right angles from the sun, relative to your position. In short, avoid the use of polarizers for skies with wides.

In the interest of being as precise as possible, this is almost completely accurate. The effect of polorizers is a function of the angle between the sun and "viewed" portion of the sky. The effect is maximized at 90 degrees and decreases as that angle deviates from 90 degrees.

This is why you see the dark spot surrounded by lighter sky in Gluwater's image.

wxwax

Nikolai wrote:

With a super wide glass it's way better to take bracketed shot (or simply develop underexposed RAW) and then use any standard blending technique to get a nice deep blue sky from there..

Yes, but then you get into difficult masking issues.

pathfinder

gluwater wrote:

In case you don't believe anyone above about the weirdness of a Circular Polerizer with an ultra wide, here is an example.
20D
Canon 10-22
Tiffen Wide Angle Circular Polerizer (made specifically for Wide Angle)

This is inherent in the way polarizers work, and the wide angle of coverage of lenses wider than about 28mm on a full frame camera.

Nikolai

Sid,

wxwax wrote:

Yes, but then you get into difficult masking issues.

That's what I thought and experienced originally, too. :

However, after mastering split blend-if controls in Layer options (after reading Dan's LAB book and hearing about them from Rutt ) this problem seem to be a non-issue in most of the cases...

Cheers!

Khaos

Yes, you'll get that dark spot, but they really help in making the colors pop and getting those nice water reflections. B+W thin on a 10-22.

wxwax

Nikolai wrote:

That's what I thought and experienced originally, too. :

However, after mastering split blend-if controls in Layer options (after reading Dan's LAB book and hearing about them from Rutt ) this problem seem to be a non-issue in most of the cases...

Cheers!

Nikolai

Blend-If

wxwax wrote:

I'm at work now and it's kinda an advanced topic to explain in a few words.. Dan's book has a whole chapter on those, or even more, IIRC...

The idea is that you can tell PS to blend (merge) two layers only if certain conditions on a certain (set of) channel (combination or single) apply.

You can control both individual channels and, in non-LAB cases, and additional artificial "Gray" one (kinda luminosity). And if you alt-click on the control markers you can "split" them and thus achieve a very smooth blending.

The easiest way to get an idea (at least, for me it was:-) is to load two arbitrary different images into two layers (same size would help, but does not matter otherwise), double-click the upper one to get to the layer options dialog and start fiddling with the blend-if sliders and channels.

It's an extremely powerful tool!!

HTH

Nikolai

Reflection

Khaos wrote:

Yes, you'll get that dark spot, but they really help in making the colors pop and getting those nice water reflections.

You're correct on this one, there is no way you can control water/glass transparency/reflection level w/o polarizers.. So in this case you kinda have to compromise

wxwax

Nikolai wrote:

I'm at work now and it's kinda an advanced topic to explain in a few words.. Dan's book has a whole chapter on those, or even more, IIRC...

The idea is that you can tell PS to blend (merge) two layers only if certain conditions on a certain (set of) channel (combination or single) apply.

You can control both individual channels and, in non-LAB cases, and additional artificial "Gray" one (kinda luminosity). And if you alt-click on the control markers you can "split" them and thus achieve a very smooth blending.

The easiest way to get an idea (at least, for me it was:-) is to load two arbitrary different images into two layers (same size would help, but does not matter otherwise), double-click the upper one to get to the layer options dialog and start fiddling with the blend-if sliders and channels.

It's an extremely powerful tool!!

HTH

Sounds very interesting. And complimucated.

Nikolai

It can non-trivial be at times

wxwax wrote:

Sounds very interesting. And complimucated.

But in case of getting a blue sky w/o polarizer it's REALLY easy :

1. Get bracketed shots or develop different exposures from RAW - one with good deep sky, another with the rest
2. Put them into two adjacent layers, sky one on top
3. Create a rough layer mask for the sky layer to include the sky and a bit under the horizon. Don't have to be precise, just make sure you got the transition line.
4. Double click the upper sky layer to get to its properties.
5. Play with Blue and Gray Blend-if sliders.

The very first time it may take you a few minutes to get what you want: seamless blending between the sky and the skyline without nasty halos. After that you won't even think twice before going there :-)

Try it, you'll like it!:):