MarkBarbieri
Semi-retired
- Joined
- Aug 20, 2006
- Messages
- 6,172
$2,000 filter? Where can I get one of those? 
Filters come in two different attachment styles. There are round filters that screw onto your lens and there are square filters (sometimes called Cokin style) that slide onto an attachment on your lens. I generally prefer the round, screw-on types except when stacking filters (putting on more than one) or using graduated filters (ones that have more filter on one half and less on the other). For polarizers, I've always used the screw-on types. Your mileage may vary.
Filters come in different sizes. The threads on the front of your lens may be different sizes. Mine range from 82mm down to 52mm. Rather than buy a different filter for each lens (because I'm all about saving money), I buy one for the largest lens I think I'll own. For the smaller lenses, I buy cheap adapters. It's possible to get an adapter that fits a smaller filter on a larger lens, but you'll get really dark corners on many lenses if you do this.
As has been noted, getting multi-coated filters will help reduce reflections and flare. Some filter makers offer a variety of filters with different types of coatings. Just looking at Hoya on B&H, they offer a Circular Polarizer Glass Filter, a Circular Polarizer (HMC) Multi-Coated Glass Filter, Circular Polarizing Pro1 Digital Multi-Coated Glass Filter, Circular Polarizer Super Multi-Coard (S-HMC) Glass Filter, Circular Polarizer (HD) High Density Glass Filter, HRT Circular Polarizing Filter. I have no idea what the differences are, but I'd stay away from the plain one because it isn't multi-coated.
Circular Polarizers are a little thicker than normal filters because they have two layers and because they have to be able to rotate. They come in two thicknesses - normal and thin. The thin ones are less likely to vignette (darken the corners of your picture) on wide lenses. The downside is that they generally don't have threads on them. That means that you can't put another filter on them (not usually a big deal) and you can't attach most lens caps to them (very annoying).
One nice trick with polarizers is that you can stack two together to make a variable power neutral density filter. The first one can be a linear polarizer but the second should be a circular polarizer. The image quality will fall apart at the dark extreme and you may get a color cast, but it can be darned handy, especially for shooting video.
My impression (not at all scientific) is that the best polarizers are the Singh-Ray, B+W, Lee, and high end Hoya. The middle tier consists of the cheaper Hoyas, Tiffen, OEM (Canon, Nikon, et al which are often rebranded Tiffens), and Cokins. You can get even cheaper no-name or counterfeit filters off of e-Bay, but I wouldn't go there.
I don't think that you'll see a difference between the top tier and middle tier in most shots. The difference will be when you have bright light directly hitting the filter. In those cases the better coatings on the better filters will reduce the reflections and flare problems you might get. Whether that is worth the extra price is a subjective decision.
I usually buy the high end Hoya filters because I find that they give the best value for the money. The only problem I have with them is that the plastic cases they come in are terrible. Singh-Ray ships their filters in really nice little pouches.
So why circular in stead of linear? They both polarize light. That means that they block light waves bouncing in one orientation and let in light waves bouncing in a different orientation. Depending on how you have it rotated, it might let in light waves bouncing up and down and block light waves bouncing side to side. The problem is that having light waves all bouncing in one direction can confuse your camera's metering and AF systems. A circular polarizer fixes that problem be scrambling the light waves after it has polarized them. This effectively unpolarizes the light waves. The first screen polarized out the light waves you didn't want and the second screen unpolarizes the remaining light. So you get the effect of a polarizer without the downsides of sending polarized light to your camera.
So when do you use a polarizer? When you want to block polarized light. When shooting skies, the filter will remove hazy polarized light and leave the darker blue light from the sky, so your sky will look darker. When shooting reflective surfaces, the polarizer will cut out light bouncing off of the surface. That makes it great for shooting water, glass, or other reflective/transparent surfaces. It can also help in circumstances that you might not suspect. I've seen cases where the leaves on a tree get much richer looking because the polarizer cuts lit bits of glare on each of the leaves.
Polarizers work best at some angles. For skies, they work best when the sun in about 90 degrees from your subject. So the sky will look darkest/bluest when the sun is on your left or right, but not when it is directly ahead or behind you. As has been noted, really wide angle lenses give a variable affect because they cover such a wide range of angles. Whether that bothers you is another subjective choice.
Be careful screwing a polarizer onto your lens. If you cross thread it and force it, it can be extremely difficult to get off. That's true of all filters, but the fact that the front of polarizers rotates makes it even worse for them.
Polarizers don't last forever. They degrade over time, so don't just leave it sitting in the sun. Also, the threads eventually get hard to turn. I'm do for a new one soon as my existing one barely turns. I actually adjust it by screwing it tighter or looser rather than turning the rotating part.
Filters come in two different attachment styles. There are round filters that screw onto your lens and there are square filters (sometimes called Cokin style) that slide onto an attachment on your lens. I generally prefer the round, screw-on types except when stacking filters (putting on more than one) or using graduated filters (ones that have more filter on one half and less on the other). For polarizers, I've always used the screw-on types. Your mileage may vary.
Filters come in different sizes. The threads on the front of your lens may be different sizes. Mine range from 82mm down to 52mm. Rather than buy a different filter for each lens (because I'm all about saving money), I buy one for the largest lens I think I'll own. For the smaller lenses, I buy cheap adapters. It's possible to get an adapter that fits a smaller filter on a larger lens, but you'll get really dark corners on many lenses if you do this.
As has been noted, getting multi-coated filters will help reduce reflections and flare. Some filter makers offer a variety of filters with different types of coatings. Just looking at Hoya on B&H, they offer a Circular Polarizer Glass Filter, a Circular Polarizer (HMC) Multi-Coated Glass Filter, Circular Polarizing Pro1 Digital Multi-Coated Glass Filter, Circular Polarizer Super Multi-Coard (S-HMC) Glass Filter, Circular Polarizer (HD) High Density Glass Filter, HRT Circular Polarizing Filter. I have no idea what the differences are, but I'd stay away from the plain one because it isn't multi-coated.
Circular Polarizers are a little thicker than normal filters because they have two layers and because they have to be able to rotate. They come in two thicknesses - normal and thin. The thin ones are less likely to vignette (darken the corners of your picture) on wide lenses. The downside is that they generally don't have threads on them. That means that you can't put another filter on them (not usually a big deal) and you can't attach most lens caps to them (very annoying).
One nice trick with polarizers is that you can stack two together to make a variable power neutral density filter. The first one can be a linear polarizer but the second should be a circular polarizer. The image quality will fall apart at the dark extreme and you may get a color cast, but it can be darned handy, especially for shooting video.
My impression (not at all scientific) is that the best polarizers are the Singh-Ray, B+W, Lee, and high end Hoya. The middle tier consists of the cheaper Hoyas, Tiffen, OEM (Canon, Nikon, et al which are often rebranded Tiffens), and Cokins. You can get even cheaper no-name or counterfeit filters off of e-Bay, but I wouldn't go there.
I don't think that you'll see a difference between the top tier and middle tier in most shots. The difference will be when you have bright light directly hitting the filter. In those cases the better coatings on the better filters will reduce the reflections and flare problems you might get. Whether that is worth the extra price is a subjective decision.
I usually buy the high end Hoya filters because I find that they give the best value for the money. The only problem I have with them is that the plastic cases they come in are terrible. Singh-Ray ships their filters in really nice little pouches.
So why circular in stead of linear? They both polarize light. That means that they block light waves bouncing in one orientation and let in light waves bouncing in a different orientation. Depending on how you have it rotated, it might let in light waves bouncing up and down and block light waves bouncing side to side. The problem is that having light waves all bouncing in one direction can confuse your camera's metering and AF systems. A circular polarizer fixes that problem be scrambling the light waves after it has polarized them. This effectively unpolarizes the light waves. The first screen polarized out the light waves you didn't want and the second screen unpolarizes the remaining light. So you get the effect of a polarizer without the downsides of sending polarized light to your camera.
So when do you use a polarizer? When you want to block polarized light. When shooting skies, the filter will remove hazy polarized light and leave the darker blue light from the sky, so your sky will look darker. When shooting reflective surfaces, the polarizer will cut out light bouncing off of the surface. That makes it great for shooting water, glass, or other reflective/transparent surfaces. It can also help in circumstances that you might not suspect. I've seen cases where the leaves on a tree get much richer looking because the polarizer cuts lit bits of glare on each of the leaves.
Polarizers work best at some angles. For skies, they work best when the sun in about 90 degrees from your subject. So the sky will look darkest/bluest when the sun is on your left or right, but not when it is directly ahead or behind you. As has been noted, really wide angle lenses give a variable affect because they cover such a wide range of angles. Whether that bothers you is another subjective choice.
Be careful screwing a polarizer onto your lens. If you cross thread it and force it, it can be extremely difficult to get off. That's true of all filters, but the fact that the front of polarizers rotates makes it even worse for them.
Polarizers don't last forever. They degrade over time, so don't just leave it sitting in the sun. Also, the threads eventually get hard to turn. I'm do for a new one soon as my existing one barely turns. I actually adjust it by screwing it tighter or looser rather than turning the rotating part.
I was telling a friend at work this morning about how I had been thinking about getting a polarizer and one of my colleagues came around the corner and said, "You have to get a polarizer! I always use a polarizer!". Granted, he is a landscape film photographer, so this doesn't surprise me, but I'm wondering if a lot of the WDW pictures that I see on these boards have been shot with a filter. I'm mostly just curious at this point and ~probably~ won't buy one before my next trip (4 days!) but...you never know 
