[ds00kg]

I am looking at purchasing some filters for my new Sigma lens (thanks Ray) but have a few questions..

Neutral Density filters; would this be useful in gaining some contrast/reducing the exposure of bright skies, or should I be using a graduated (gery) filter?

Polarising Filters; What's the main difference between the uber expensive Canon Polarising filter and the cheap 7dayshop ones? Quality of build/sharpness/image quality/all of the above?

Macro close up filters; These seem a great way to boost your macro shots but do they reduce sharpness or distort the image?

Thanks

[VinnyP]

Originally Posted by ds00kg

Neutral Density filters; would this be useful in gaining some contrast/reducing the exposure of bright skies, or should I be using a graduated (gery) filter?

A Neutral density (ND) filter is just used to reduce the amount of light getting to the film or sensor. They are used to give more creative control so you can use a wider aperture, slower shutter speed or very occasionally higher ISO. To reduce contrast you need a graduated ND. These can be screw in but far more flexible are the rectangular filters that go in a filter holder. The best known brands are Cokin, Hi Tech and Lee. To make matters more complicated they come in "hard" and "soft" edge depending on how gradual the transition from light to dark is and they come in various strengths.

Polarising Filters; What's the main difference between the uber expensive Canon Polarising filter and the cheap 7dayshop ones? Quality of build/sharpness/image quality/all of the above?

I can't say for sure because I haven't used either the 7 day cheap ones or the Canon ones. What is generally the case is that cheap filters have little or no coating on the glass and use lower quality glass. This leads to glare, reduced contrast and muddy colours. They may be less well built as well. The Hoya Digital pro 1 and HMC super are very good and B&W and Singh Ray are thought by many (including me for what it's worth) to be the best.

Macro close up filters; These seem a great way to boost your macro shots but do they reduce sharpness or distort the image?

They can give good results but yes can give distortion, be tricky to focus and reduce image quality. Another cheap alternative are extension tubes that have the advantage of not adding any more lens elements into the equation but with shorter focal length lenses can give pretty good magnification. What you lose is a little bit of light and the ability to focus to infinity.