Filters are essential part of photography and lenses. Most of filters which were essential in film photography has been discontinued by emerge of digital photography. Still The UV and circular polarising are the two main line which remained integral part of photography.

In filter making Hoya remains the leading in the market, by producing circular polarising, UV and macro filters. It has many lines like Hoys HD, s HRT, Pro1, SHMC, HMC etc.

Its worth mentioning that Canon Nikon, Sigma, Kenko produce their own line of filters, ranging from circular polariser to UV and soft filters.

You can alter a picture by using software, but still you need to protect your lens by UV or Protector filters and you must have a circular polariser for sure to get the best contrast. Nikon keeps producing the NC (Neutral Clear) filters