Filter for Sigma 24-70 2.8

I am looking to pick up a filter or two for my 24-70mm 2.8 Lens. It has a thread size of 82mm which makes filters rather expensive, but worth it (i'd hope).

I shoot a lot of portraits, including events for my university, and want a filter that will not only protect the front element (as filter's do) but also add to the image in some way. I've gotten recommendations for circular polarizers, but do not know much about filters. Any feedback would be very appreciated.

If you're not looking for a specific effect, then just get a clear glass one - there is no filter which will make all your images better. A polariser reduces reflections which can cause increased contrast in the sky, on foliage outside, and make water look clearer, but this comes at the expense of a couple of stops of light.

Nerrep wrote in post #6312308
If you're not looking for a specific effect, then just get a clear glass one - there is no filter which will make all your images better.

Ok. I wouldn't assume any filter would make the images better, sorry for poor choice of wording, I just knew that polarizers affected the image. Is it desirable to use? Could someone include an example perhaps?

Try this for some information.

http://www.dpfwiw.com/​filters.htm#why

also www.hvstar.net markets filters at very good prices. It took me about a week to get mine from Hong Kong.

Equivalent prices:

Hoya 82 mm PRO1 DIGITAL Circular Polarizer Filter DMC *+Cleaning Cloth+Filter Holder+LensPen
hvstar price: $82.50

Hoya 82mm Circular Polarizing Pro 1 Digital Multi-Coated Glass Filter
B&H price $269.95

http://www.ephotozine.​com/article/Polariser-guide

Some examples of what a polariser can do for you. Generally desirable in bright sunlight or where you want to try and reduce reflections. Not so much beyond that when you consider the two stops loss of light.