Polarising Filters

innisfree

I've found these filters in the past to range from E70 - E100, but found this one just now:

http://www.7dayshop.com/catalog/product_info.phpmanufacturers_id=&products_id=7700

ST£11.99 seems a bit odd. So am I right in presuming the quality of these filters can vary drastically? And so, it is pretty certain this filter will have poor results compared to one of a higher price?

innisfree

Oh, and also, am I right in purchasing a LINEAR filter, rather than ciruclar one, because I'm using a 58 diam SLR lens.

norma

The quality of filters can vary drastically. Some are made from resin, some are glass. Some are coated to prevent lens flare, some are multi-coated to do an even better job, and some aren't coated at all. How you can tell whether the coating on a filter is sufficient is to see if you can see reflections on the surface of the glass; if the filter is sufficiently coated, you shouldn't see reflections on its surface. There are also 'construction' factors, for want of a better word. For example, with cheaper filters, sometimes the glass is too loose within the metal ring.

How much you spend on a filter depends on things like the quality of your lenses to begin with, how often you would use such a filter, and whether or not your photos are for commercial use. As with all things, you get what you pay for.

Finally, if your lens is autofocus, you will need a circular polariser. The linear polarisers interfere with autofocusing and are only suitable for manual focus lenses. Another advantage of circular polarisers is that you can vary the intensity of the polarisation. This is something you will see through the lens as you rotate the filter.

Considering a polariser is something you will often use in bright sunlight, I highly recommend one with a multi-coated surface to prevent lens flare.