Thin or regular filters

[DragonJade]

I'm getting a 20D soon with a Sigma 18-50 F2.8 EX DC and a Canon 50 F1.8 II.
I read somewhere that I had to use thin filters to go with lenses that were built for digital cameras. Is that right? Am I ok with a regular sized filter on the 50mm?

Thanks.

[lancea]

You will be fine with a "regular" on the 50. You only need thin filters (with low rims) on true wide-angle lenses. For example, you don't really need a thin filter at 18mm because of the crop factor of the sensor making it effectively only a moderate wide-angle. However if you put the same lens on a camera with full-size sensor you probably would need a thin one. Also if you are stacking filters, e.g. a polariser on top of a UV, you will probably need thin filters at your widest zoom to avoid vigneting. Of course if you're buying expensive filters it might pay to get thin ones for when you buy a camera with a full-size sensor. But you certainly don't need a thin filter for the 50.

[DragonJade]

So the only difference between the regular and the thin filters is the amount of the thread? Glass is exactly the same?

On a secondary note, how to Kenko filters rate?

[robertwgross]

There is another trick that you may run into with thin filters. Some brands have screw threads on the camera side (so that you can attach it to the lens) but they have no screw threads on the outer side (so nothing can attach to it). That would be tricky if you were trying to stack filters. I have heard of some brands that have both threads, but it is best to ask first if that is a concern.

---Bob Gross---