Actually, many people are lazy when nthey come to using filters. Most landscape photographers will have the following filters in their bag when they travel for shoot:
1. ND filters (2,4,8) - this is the allow slower shuttle speed to be able to be used.
2. ND Grad filters - these are usually used to bridge the gap of the light inetensity between the foreground and background. especially like if the sky and the scene in front is more than 2 stop deifference. The graduation helps to make it more subtle in the light balancin between the horizon line. Typcially, the better brand filters will have hard grad or soft grad. Hard grad is for a very defined skylight or horizon whike soft grad is more for a fuzzy dividng skyline. The filters are used depending on situation.
3. ND 400/800 filters - this is a rare filter where many UK landscape photographers like to use. It drops the light to 9 stops allowing u to shoot moving thing like water, waves to become like white mist.
4. Warm up & Cold filters. Typcially the differnt intensity of warm up in the 81 series and the cold blue tone of 85 seris of filters. More for creating the ambience and mood in yr image if the lighting is not fantastic or to the atmosphere that you need.
5. Circular Polarisers - this is to help you give more intense colours and cut out excess UV rays. C-PL filters have to be used with care and the filter should be rotated in place to see the intensity at each turn of it. It has a notorious effect of making the blue sky into very intense and fake blue if not use properly.
Personally, there are some filters that I enjoy using before:
1. Singh Ray's Soft & Hard grad ND Filters
- These are the top end filters that all serious landscape photographers sweared by. Especially the Galen Rowell series of SinghRay filters. Very well made and the colour consistency is unmatched by others.
2. Singh Ray colour intensifier
3. Singh Ray warm up circular Polariser (the Robert Moose series)
- This series of warm up circular polariser are favoured by nature photographers, Robert oose who specialised in shooting wildlife like grizzly bear. These C-PL filters added tints of colour (eg. yellow with blue)to the CPL and give it more inpact and intensity in the colour. But a good knowledge of colour complement and lighting is essential to tap on these filters optimally. Anyhow use will give you disastrous effect. LOL!!!
But having mentioed all above. The Singh Ray filters are unbelieveably expensive. So, most people would go for the next cheaper and even more cheaper alternative and accepts a compromise. Most of people wuld choose the COkin slot in type of gelatin filters for easier adaptation to all filter ring size.The typcial ranking in terms of budget & quality is probably (IMHO) in the following order (from the best in quality & cost):
1. Singh Ray
2. Lee Filters
3. Cokin
4. Tian Ya or other Chinese equivalent
You can take a look at some of photos where I have extensively used these filters. They can be found at:
www.flickr.com/photos/jeffreyyap
or you can also access another CS guy's portfolio at
www.flickr.com/photos/chkese
He also uses Singh ray filters extensively.