Enlighten Me!

[Faelan]

I just picked up my first real camera a couple days ago. No more point and shoot for me! I got a Digital Rebel XT, the big Canon Gadget bag, 6gigs total of CF, 3 batteries, a UV filter and a tripod. Now here's the real basis for my post...

Tell me about filters.

What are the advantages of filters (UV, IR, Polarizing, etc.) and when do you use them?

Thanks.

[coreypolis]

UV IMO are worthless. They don't do much besides reduce AF, and image quality. Front elements are very well made and designed to withstand daily use. If you're by sand or in the rain, it might not be a bad idea, but don't go get a $150 uv for every lens.

Polarizers are a must, they can't be duplicated in PS and can really add life to an image.

IR is a specialty filter, I'd read a lot of reviews and make sure you know what all it entails and how to get the most from it.

ND's are great for landscape or any shot where you can set it up on a tripod for a while and not worry about the shutter speed.

In reality most are fine with only a polarizer (you need a circular). Keep in mind they reduce the light input by ~ 2 stops, so only use them when theres enough light to avoid camera shake

[crn3371]

The main reason for using a UV filter is for protection. Whether to use one, or not, is a hotly debated subject, some use them, some don't. I'll let someone else open that can of worms. Polarizers are used to remove glare, or reflections, and also used in landscape situations to get bluer skies, and whiter clouds.

[Jon]

Whatever filter you get, buy a good multicoated one. Heliopan, B+W and Hoya (their S-HMC or better) are reliable; other brands and lesser grades are asking for trouble. I use B+W MRC UV filters on my lenses for protection from FOD in high winds (including jet- and prop-wash), undergrowth, or from dog noses, any or all of which are common environmental conditions where I shoot, and I haven't seen problems.

[DaveG]

Originally Posted by Faelan

I just picked up my first real camera a couple days ago. No more point and shoot for me! I got a Digital Rebel XT, the big Canon Gadget bag, 6gigs total of CF, 3 batteries, a UV filter and a tripod. Now here's the real basis for my post...

Tell me about filters.

What are the advantages of filters (UV, IR, Polarizing, etc.) and when do you use them?

Thanks.

I have a UV filter on every lens I own, except for my macro which has the front element recessed back about an inch, so it's very well protected. Lens front elements are NOT - even slightly - resistent to scratches, blowing sand, and just the regular wear and tear of using your lens. They are just pieces of glass with some very expensive coatings on their surface. Even cleaning the lens damages it very very slightly. Filters keep that front element protected and I clean the filter not the lens.

About every two or three years I replace my UV filters, and I do that because I can see the accrued damage. I also do it with a big smile on my face because filters are cheap and lenses are not. Even if you accepted the idea that a UV filter will reduce the sharpness of a lens - and in my opinion a good multicoated UV will not impair resolution - how does a scratched front element fit into that equation? At some point you would be saying, "I don't want the filter to lower my lenses sharpness, but I don't mind using a damaged lens." Sure you'll get a seriously damaged lens fixed but what if it just is a little wear on the multi-coating? No you'll use it and probably won't be too concerned. Besides are you willing to send a lens back for a new front element every couple of years?

The other thing is the resale issue of your gear. Anything I own I'll sell, if I see an upgrade possibility. Well it helps if my stuff is in excellent shape. If I'm buying a used lens I point it at a light source and look through the back element towards the front of the lens. If the seller didn't use a protective filter I will be easily able to see pitting and any other damage done to the front element and I won't buy the lens.

As for other filters the only two that I use (and I bet I have over 50 filters, sigh ..." are a circular Polarizor and a Neutral Density. As another poster wrote, the Polarizer does effect the image in a way that Photoshop can't match. I also use the ND filter when I'm shooting moving water. I've found that it takes about an eight second exposure to make the waterfall look like I want it to, and that means having a way to knock off extra light.

[Curtis N]

Filters were often used with film to augment the color, usually to make the light source match the film, or for creative effects. Those aren't necessary with digital.

Circular polarizers are used to reduce reflected glare from non-metallic surfaces and make the sky look bluer. But they need to be rotated on the lens to achieve maximum effectiveness, and if your lens' front element rotates when it focuses (like the 18-55 kit lens), they can be a bit hard to use.

[Ukuleleman]

Originally Posted by Curtis N

if your lens' front element rotates when it focuses (like the 18-55 kit lens), they can be a bit hard to use.

The front element on my 18-55 Kit lens doesn't rotate! it just goes in and out, did they change them? I have only had mine for 4/5 months I am interested because I have just bought some filters for my lenses and I assumed that a 'Circular Polariser' would not require any particular orientation since it polarises in a circular fashion. Am I wrong in my assumption?

[Jon]

Yes, you are. It still polarizes in the normal manner, however through use of a "quarter wave plate" behind the polarizing material, it "de-polarizes" the light which has gotten through the filter, so your AF system (which is behind a partially-reflective mirror that also polarizes the light passing through) gets some image to work with.

[Savagebasher]

Originally Posted by Ukuleleman

The front element on my 18-55 Kit lens doesn't rotate! it just goes in and out, did they change them? I have only had mine for 4/5 months I am interested because I have just bought some filters for my lenses and I assumed that a 'Circular Polariser' would not require any particular orientation since it polarises in a circular fashion. Am I wrong in my assumption?

the front element on the kit lens rotates while focusing

[Curtis N]

Originally Posted by Ukuleleman

The front element on my 18-55 Kit lens doesn't rotate!

Watch it focus sometime. Better yet, try manual focusing.

[Ukuleleman]

Yeh, your right guys, my apologies, I wasn't focussing, I was zooming!

Jon, thanks for your reply re the filter orientation, still a bit confused though, if it does in fact still polarise in the normal manner as you say, do I have to do anything more than just fit it to the lens, it would seem that I must do something to compensate for the the rotation of the front element
of lenses such as the 'kit'. as pointed out by Curtis.

[Jon]

Right - you'll have to make your final adjustment to the polarizer after you've focussed. Obviously this makes AI-Servo a real problem.

[Ukuleleman]

Gotcha, many thanks.