Circular polarisers: difference ?

[donoreo]

I have not found a clear answer to this. What is the difference between cheap circular polarisers to expensive ones? Obviously there can be a build quality difference. How about the effectiveness of the polarising, is that different? What would really be the difference between my cheap Camlink and a Hoya regular to a Hoya pro? I know the Hoya Pro are multicoated but what does that give me, does it cut extra glare? Lens flares?

This is one of those things I have seen bits and pieces of here and there, but never all explained in one spot.

[ianpinion]

The main differences between the cheap ones and the pro quality circular polarising filters, are:

• the thickness of the surrounding rim. The cheaper ones are much thicker and can cause vignetting on wide angle shots.
• the multicoatings that reduce lens flare and other aberations. This is a very tricky manufacturing procedure as the coatings have to be baked on at high temperatures without damaging the thin sheet of polarising material held between the two layers of glass.
• the optical quality of the glass used in the filter is superior causing less distortion.

[donoreo]

Does anyone know about the polarisation effect though? It is better on more expensive ones? The rest makes sense and I knew those, but I have never seen anything that compares this.

[Cathus]

also the more expensive ones are made of stronger glass & can withstand more punishment than the cheaper ones, check out some YouTube videos for Hoya Pro filter strength

[donoreo]

I would never think to consider the strength of the glass, just the optical quality. I cannot find a review/test where anyone has done a side by side with CPs. If anyone knows of one, pass it on

[chris-p]

I don't know of any back to back reviews but it definitely can make a difference.

I bought a really cheap 67mm c.pol a few years ago. When I say cheap, I really do mean cheap. It was about £7.50. It didn't polarise at all. What it did was give everything a yellow or a blue tint depending on the rotation but I checked it on water and glass and it didn't polarise.
I even did the TV trick and not a sausage.

If the filter actually polarises, then it should work. There shouldn't be a difference in polarisation ability between cheap and expensive filters. Light is of the same wavelength range wherever you are on the earth (within reason, anyway) and that's all there is too it.
As the others have mentioned - the main difference is in build quality and robustness.

[donoreo]

Ok, so it is works or does not work. It has never been clear. I know mine cuts glare from water, but does not do much for the sky. Perhaps I need to work on using it better. I think I will still get a better one for build quality and optical quality.

[OldBoy]

Originally Posted by donoreo

Ok, so it is works or does not work. It has never been clear. I know mine cuts glare from water, but does not do much for the sky. Perhaps I need to work on using it better. I think I will still get a better one for build quality and optical quality.

Remember, you need to be at right-angle to the sun, to get the full effect of the filter on blue skys. The dearer CP's filters have better glass, so reducing distortions on the final image.

[donoreo]

Originally Posted by OldBoy

Remember, you need to be at right-angle to the sun, to get the full effect of the filter on blue skys. The dearer CP's filters have better glass, so reducing distortions on the final image.

I know you need to be at a right angle, but figuring that out can be tricky. I did recently learn that some CPs have a mark on them and you point that at the sun. I do not know if mine does.

[KeithT]

I think it is like most things in life: you get what you pay for. A good quality filter is a joy to use, easy to keep clean, and fits the lens like a glove. A good filter is usually made from top quality optical glass and will not distort images in any way shape or form. Good filters are coated both sides and will have special coatings for digital use preventing flare and ghosting.

Cheap filters may not be totally flat; they may be made from optical glass that has been rejected by other manufacturers; will most likely have cheap aluminium frames that can jam solid when you put them on your lens and cause damage to your lens filter thread when you try to free them; may not be coated properly.

As I say — you get what you pay for. My opinion is buy cheap, buy twice.

edit: I have a 77mm Canon CPfilter. It cost about 150 quid when I bought it, but to be honest, I hardly ever use it. What you should be asking yourself is 'DO I REALLY NEED THIS FILTER?'

By the bye, if you have a cheap polariser and want to know if it is really a circular type, or just two linear filters put together. If you hold it up to a mirror and look through the face side at the reflection, it should show you completely dense black glass that you are unable to see through. If you can see through the filter reflection in the mirror, it aint a circular polariser.