This is a revise version of what I wrote a few years back on Filters.
This review is for those who are new in the world of photography; the veterans might find something useful too. It is base on the filter that I have.
Skylight, UV filters, protection filter (clear optical glass):
These types of filter serve very well as lens protection because they are relatively cheap to buy. They come in great varieties; single-coated (HOYA green), multicoated (HOYA purple), PRO, etc. Skylights filter then to warm up the image a little as it add more red to your image. UV cuts out Ultra-Violet light. The higher the altitude the bluer the environment gets, so UV filter helps reduce the bluish tone. But at sea level, you will not notice any differences. I use UV on all my lens as a protection filter. I also find the yellowish/redish tone a little annoying.
For protecting the lens from environment, ask youself these. What surface would you be more comfortable wiping sand off from? glass front element or the filter surface? If you happen to scratch it, then just buy a new one.
Polarized filter is one of thsoe filter you should have in you bag. It works by rotating the secondary ring on the filter to adjust the intensity. It works by cutting out the light rays that gives causes reflection. Example being if you are shooting water surface, with the filter turing in a correct amount will allow you see under the water (cuts out the glare on the surface). It work with any reflective surface such as window, waterfall, and sky (make it bluer). It also cuts out the light by as much as 2 f-stop.
Most waterfalls shoot would need polarized filter as you want to have the least amount of distracting reflections and because it cuts out light, you can now expose your image for a little longer.
Cokin are unique in a sense that you just drop the filter into a hold, change when ever you want. Great range and reasonably priced. I am now sponsered by Cokin. http://www.qualitycamera.com.au stocks Cokin range, they are in Perth but next business day shipping. TED in Sydney CBD (on special order, takes 1-2weeks). Cokin come in many sizes, from A, P, Z-PRO and X-PRO.
A is way too small for DSLR, unless you are not planning to mover from 58mm.
P (100mm x 84mm) is the next size up, it will fit up to 77mm threads, can hold up to 3 filters with standard holder. Problem only occur when you have an ultra-wide angle lens (Canon 10-22mm, Sigma 10-20mm, etc) – vignette occurs only when I go below 12-14mm. You can buy wide-angle adapter (hold a single filter) which you can shoot at 10mm (16mm in 35mm terms). This is a much cheaper alternative than going up a size. Or you can even buy a 3 slots holder and cut it down to 1, I did. But buying one would be easier. REMEMBER, vignette only occur if you go below 14mm for the 3 slots holder and non on the ultra-wide holder (providing that you take out your UV (Protection) filter).
Z-PRO is much better (150mm X 100mm) and cost 3x as much as the P series. Same size as LEE filter. I finally end up buying this as i couldn’t be bother to take the UV out of my lens anymore. Z-PRO can hold two filters or reverse (flip) it to hold one. To be honest, after have been using it since May 07, i think that it isn’t worth it. P works much better as the filter cover mose of the lens’ front element. Z-PRO is much bigger and spilled out (15-20% on each of the long side) over the side of the front element. Confused? Say a GRAD ND, with P, the darkest part start at the top of the lens all the way down to clear at the bottom. Z-PRO, starts out at about 80% dark (then other 20% is outside the glass), down to about 20% grey. So P works much better with the full effect, and it’s way cheaper for someone starting out.
X-PRO is a little bigger again. They are aimed for Large format camera or commercial film production, TV shows. I personally have no experience with these product. Some people are using these now for new super-wide digital lens such as 14-24 Nikkor on Full Frame cameras.
What you would need;
1. Adapter ring in the size that will your threads on the lens (77mm, 67mm, 58mm, etc)
2. Filter Holder.
3. Filters (I highly recommend the 121M (ND4 Grad that works on most situation) and 124 Tobacco Filter (GRAD Orange, peferct for sunrise and sunset).
UPDATE: just found a really cool new way to stop vignette on the Z-Pro.
If you take the spacer out and put it at the very front – the vignette goes away…..which is very very cool at my 10mm
While you are there, (this review isnt’ bias, I have written this way before Cokin ask me to put a profile up). Check out http://www.cokin.com/gallery.html
I have been using Cokin Graduated Neutral Density (Grad ND) for a few years now, these has a darker upper half, then it gradually reduce to clear at about halfway point. I use it for architectural shot, landscape, as well as environmental portrait (when I need to reduce the exposure on the sky down). Why do you need these type of filter? Because of the sensor in digital camera (no matter how advanced or how expensive they are). They can not replicate the dynamic range of our eyes. Meaning that the sky will always be about 2-3 stop brighter than the ground. If you shoot landscape with sky in them, if you point your camera at the sky, the metering will read and calculate base on the sky, chances are, the sky will be beautiful but the land will be too dark. And if you point the camera at the house, the sky becomes brownout. So slap a grad ND on and shoot away, shooting at the house, the ND will bring down the exposure of the sky. You can calculate how much you would need base on how bright the sky is. I do not go outside without one of these.
Cokin do have other effect GRAD ND filter, bought in from the old non digital day; grad blue, grad red, stars, etc. I do have collection of Tobacco (red) Graduated filter; it helps enhance sunrise or sunset shot. I use Tobacco filter a lot for my Sunrise and Sunset.
Full Neutral Density filter helps bring down the lights level without effect the colour of the photo. Ever wonder how to shoot waterfalls and get those flowing water effect. The answers are here, because you need exposure time running longer into seconds. Without the filter, the whole scene becomes blownout. So you use the filter to let less light into the camera, hence longer exposing time. They usually come in ND4, ND6, ND8, meaning it will stop the light by 1, 2 and 3 stop respectively. You can get other one that have 10 stops for those extra long exposure.
You can buy screw-in or cokin type.
Screw in to you front element of the lens to make minimum focusing distance closer. Can be use as macro lens substitute as well. Example, on my 75-300mm IS USM, minimum focus distance is 1.5m, if I slap the filter on, this will bring it down to about 0.2m.
Hope these clarified a few things, drop me a line if you need anything else.
21 Jan 2013: Nice video explaining about filters – http://vimeo.com/singhray/inthefieldvideo