lorenww Loc: St. Petersburg

I went out and got a cheap SunPak CPL and took it on vacation. I set it so that the skies were bluest but now have a blue cast to shadows in many of my shots.
I have used the polarizer many times before and have never noticed a blue cast to the shadows.
My question. Do all CPL's do this or just the cheap ones?

MT Shooter Loc: Montana

Just the cheap ones like Sunpak, Quantaray, Zeikos, Promaster, Beike, and all the other lesser known Chinese knock-offs. Cheap glass is always crap, no matter how good of a lens you put it on.

krispix Loc: London - UK

Succinctly put.
Quality or Economy. Pick one.

dpullum Loc: Tampa Florida

MT Shooter said in part: "Cheap glass is always crap"

Cheap is an emotive word, using the word "low cost" leaves one's mind open to evaluation based on facts.

We must remember that most of the "non crap" is made in the same factories as the "crap". Changing specifications and manufacturing techniques to make "crap" would be nonprofitable. Perhaps some low cost filters are low end of the spects. We covered CPFilters in other UHH forums and part of the problem discussed there is the problem with focus of some cameras. CP is achieved by putting a 1/4 wave disruptor between two linear pol filters. The choice of the 1/4 material may react differently with different cameras.

The blue cast can be adjusted out as can any cast that results from lighting and choice of wrong WB during shoot.

lorenww Loc: St. Petersburg

@dpullum, I had just gotten back from my trip and only viewed the jpg version. Opened in ACR and the white balance was way on the cool side (Auto white balance). slid it up warmer and things looked normal.
Never had that happen before with my "cost effective" CPL. ;)
Thanks for the replies.

nikonshooter Loc: Spartanburg, South Carolina

Do not take this wrong......but think about it. We spend hundreds even thousands of dollars for a lens.....and then we often put a another layer of glass, skylight, polarizer, or ND filter that can bring distortion, color cast, stop+loss, and focus issues to your otherwise state of the art system.

There is another issue, how and when to use a polarizer. I know one photographer in our Guild that keeps one on when shooting outside in daytime - he said it shows a richer blue sky - whoop-d-doo.....what does it do to the rest of the scene. In some cases it is badly needed, in others - no, no, and more no. Do not run under the assumption that this filter will render better in-camera colors in all outdoor shooting situations.

jerryc41 Loc: Catskill Mts of NY

I had always used the "less expensive" polarizers, but then I did some research and got a couple of Marumi filters. They were highly rated. By the way, I use the term "polarizer" because calling it a lens or a filter can get an argument going here. :D

http://www.ephotozine.com/article/polarisers---a-guide-to-using-polarising-filters-4757

http://www.ephotozine.com/article/guide-to-buying-a-polarising-filter-131

http://www.lenstip.com/115.4-article-Polarizing_filters_test_Results_and_summary.html

slickrock Loc: jacksonville

Go with quality filters-you can't have any weak links. Singh-Ray makes a 1.5 stop warming polarizer . Look into what they offer and buy once.

lightchime Loc: Somewhere Over The Rainbow

How true. I had a Quantaray CPL and it terribly softened my images. It finally came off my expensive lens and rolled into the water at Babcock State Park in West Virginia. The best thing (or worst) that I ever lost. There was never a color shift other than heightening the colors.

I think that the title is not being appreciated. The OP is talking about shadows. Depending on the time of day, sensors pick up shadows as blue. The filter may be a piece of crap, but in this case it is doing its job of saturating a natural phenomenon.

chapjohn Loc: Tigard, Oregon

I also agree with dpullum. ACR will also adjust jpg images. Use "open as" to get to ACR with a jpeg.

I have Sunpak, Ziekos, and Promaster CPL's and don't have a problem.

twowindsbear

Post some of your 'blue' pix?

lorenww Loc: St. Petersburg

Here are the images as well as a polarized shot and one with bare glass.
The first shot is the blue shadows which I am now convinced it is a WB issue.
Second is with the CPL (Ybor City).
Third is bare glass.
I'm peeping and don't see a quality loss (with my untrained eye) with with my cost effective filter.
I'll let the pros point it out.
Thanks for looking and appreciate the advice.

dpullum Loc: Tampa Florida

Mystery solved!! Lightchime stated: "filter rolled into the water at Babcock State Park in West Virginia." There has been lot of concern about the water at the park being decidedly bluer than last year. And to think one fumble fingers photographer and a cheap CPFilter is the source of the sudden color shift!!
=======================
Nikonshooter (no one calls themselves Polaroidshooter, or Viviatarshooter etc. Oh well name dropping allowed) Wait a minute, a lens is a multi-layered, surface ground to curvature specs, spaced just so, moving elements in a zoom, refractive compensating mixture of glasses, highly engineered. Each element is designed to end-up with red and blue ending as a point rather than spread with chromatic aberration.

In contrast the filter is a flat glass surface. Usually gravity takes care of making the glass flat... they have been doing that for many years. For filters metals are added or a plastic sandwich is made. But filters are fundamentally just a pass thru situation light is not bent until it hits the lens. They are much easier to make. No reason to be expensive except to make people who want to pay high prices for "special" filters. (yes, non glare surface can be better on different filters, except on IR where none is advised )

lightchime Loc: Somewhere Over The Rainbow

Love he simplicity of your information. As for your humor, well we know of your simple thoughts.

krispix Loc: London - UK

It's true what you say, except we are discussing specifically CPL filters. A polarising filter cannot be made in glass, it has to be a polymer plastic which is then sandwiched between two pieces of very thin, optically flat glass. The cheap filters however, are bonded in a (relatively) flat resin which probably fails to measure up to the ground & polished surface of one with a high price tag. If the surface is anything less than flat you will start seeing distortions creeping in. This is not to say that you might be lucky and get a good flat one, but if you get a bad one (and I have seen them) just try getting your $10 back from China!