New filter for new lens

[betagoat]

I'm purchasing a telephoto lens for my digital rebel - a Canon 100-300/4.5-5.6.  I was going to purchase a filter as well, just for protection sake.  Are there specific brands as well as a type of filter that are best?  My goodness there are filters for every day of the year - it's a bit confusing.  Thanks
Andy

[Bob Atkins]

If you want to use a filter mainly as protection, the best choice would be a multicoated UV filter from a name brand manufactuer such as Tiffen, Hoya or B+W.

I think the Hoyas probably represent the best combination of value and performance and something like this Hoya 58mm multicoated UV filter would be a reasonable choice.

* Hoya 58mm Multicoated UV Filter

[betagoat]

Thanks for the info

[lukeap69]

Bob

In your own experience and opinion, does the UV filter degrade or affect the IQ of the lense?

[Bob Atkins]

As long as you use a good multicoated filter, you should not see a drop in image quality.

Poor quality filters can degrade the image and uncoated filters can result in increased flare under adverse lighting conditions. It does not pay to buy the cheapest possible filters.

[lukeap69]

Thanks Bob.

Another question, will it be a good idea to use adapter ring for circular polarizers for lenses with smaller filter mount size?

[Bob Atkins]

Not really. You can adapt larger filters to smaller lenses if you just want to buy one set of filers. So if you have a lens that needs 77mm filters and another that needs 58mm filters, you can just buy the 77mm filters and use and adapter ring (77 to 58) to mount them on the smaller lens. The disadvantage is that the 77mm filters are more expensive and with a larger filter on a lens you can't usually attach a lens hood.

If the filter is thick and the lens is a very wide angle lens, sometimes a filter can cause vignetting. For example if I use my standard 77mm Tiffen polatizer on my EF-S 10-22, at 10mm the extreme corners of the image are darkened due to obsruction by the filter. I could either buy a thinner filter (which many filter manufacturers have), or I suppose I could try mounting a much larger filter on the lens and using an adapter. However an adapater adds thickness, so if the filter was only slighly larger (e.g. 82mm), it might not help.

For normal lenses (say with focal lengths more than 24mm for full frame and 15mm for cropped sensors), vignetting due to filters is very rare.

[lukeap69]

I was actually thinking of buying hoya 77mm circular polarizer and adapter ring for 67mm, 62mm, and 58mm. I was also thinking of the lens hood issue. I might settle for 67mm circular polarizer at the moment to be used on my Tamron 17-50.

Thanks