Which Filters for Canon Lens? Is Cokin a Bad Idea? Specially for the 24mm 1.4 II

[Snook]

Wanting a good filter choice for Nuetral Density and Polarizer filters for my 24mm and 50mm L lens... I have been using a Hoya circular for my 24mm 1.4 II but is leave half the sky light with a really dark pacth in the middle..
Can anybody recommend goos quality filter system for my 5DII mainly for shooting Video but also photography would be great...
Not sure if to go with Cinema type filters with a Mattbox or keep it simple and be able to use for photography aswell with out all the extra bulk...
Thanks for any suggestions
Snook

[Owin]

The unevenness of the polarisation effect is an issue with using polarising filters on lenses wider than 35mm. There are many articles on the web to explain if you search for an explanation.

As for a good filter manufacturer, I use Lee Filters.

[Snook]

What would you recommend for wide angle lens 24mm? Is linear the only way to go?
Thanks
Snook

[francois]

Snook,
As suggested by Owin above, I would be very careful with uneven polarization on WA lenses. Once overdone, I found it very difficult to correct in post-production.
I don't have version II of the 24mm but I've used Singh-Ray (http://www.singh-ray.com) polarizers (thin & normal) without any problem. By the way, you want to use a circular polarizer not a linear.

[Snook]

I Thought the coverage problem was due to the wide angle and the circular not being able to cover the 1/2 of the lens?
What does Linear do that is not good?
I thought linear covered the whole filter not the 1/2 like circular does....
Thanks for your help.... I am aslo looking for good Nuetral Density filters to be able to shoot video in full day light and get less depth of field when shooting at 60/th
Thanks again
Snook

[Slobodan Blagojevic]

... Is linear the only way to go?...

There is no difference between circular and linear polarizer when it comes to their visual effects. The only difference is that certain cameras' metering and autofocus systems might be fooled by a linear polarizer, hence the circular is a safe bet.

[Slobodan Blagojevic]

... I have been using a Hoya circular for my 24mm 1.4 II but is leave half the sky light with a really dark pacth in the middle..

Uneven polarization is a natural phenomenon, unrelated to the type of polarizing filter used. The area of the sky perpendicular to the sun shows the strongest polarization effect (i.e., results in the darkest sky). It is easy to determine which part of the sky will have the strongest polarization: form a letter L with your thumb and index finger, then point your thumb to the sun... your index finger will then point to the sky area with strongest polarization. Since wide angle lenses show so much sky, it is inevitable that you will notice that some areas are lighter than the one with the strongest effect. There is no way to avoid it (with super wide-angles), other than minimizing the effect by not turning the polarizer all the way (to its strongest-effect position).

[ErikKaffehr]

+1

BR Erik

Uneven polarization is a natural phenomenon, unrelated to the type of polarizing filter used. The area of the sky perpendicular to the sun shows the strongest polarization effect (i.e., results in the darkest sky). It is easy to determine which part of the sky will have the strongest polarization: form a letter L with your thumb and index finger, then point your thumb to the sun... your index finger will then point to the sky area with strongest polarization. Since wide angle lenses show so much sky, it is inevitable that you will notice that some areas are lighter than the one with the strongest effect. There is no way to avoid it (with super wide-angles), other than minimizing the effect by not turning the polarizer all the way (to its strongest-effect position).

[francois]

Slobodan has explained the issue of circular  vs  linear and uneven polarization but there's also Michael's article on polarizer filters:

http://www.luminous-landscape.com/tutorials/polarizers.shtml

Edit: uneven polarization can also be present of you use a polarizer with a long lens and stitch photos to assemble a panorama.

[PierreVandevenne]

There are also other issues with interferential filters. Most bandpass filters and I assume thin film polarizers (I couldn't find any real manufacturing information on Cokin filters, but Wikipedia seems to agree with what I believe) rely on interferences to do their jobs. The problem with interference is of course that the angle of incidence of the incoming light matters a lot (astronomical filters for example are often provided with a range of acceptable F/D ratios): using a wide angle lens wide open is likely to cause all kinds of fancy effects. Here is for example a shot taken with an objective interferential filter at 24mm 2.8



Using a filter further down the optical path where the light is more perpendicular to the sensor plane (for example in front of the sensor like in the EOS clip filter families) works better for astronomical applications, but it is a bit hard to turn a polarizer in that location...