sigma 150x500 filter?
 

My question is,do I need to use a filter on my lens? if so, what would be the one to get?and for what effect if any,? or to protect the lens itself,??
I use the lens only for wild life,well and the camera:rolleyes:
any addvice would be helpfull,
thanks for looking in,all the best Ian...

There are two reasons to use filters - firstly for the effects that they give and secondly a protection for the front element of the lens. If you want a photographic effect that a specific filter will give then it is clearly worth using one. However whether it is worth fitting a UV filter purely for protection is another matter. Some people always fit protective filters, personally I never do. I tested some filters on my lenses and found that they had a detrimental effect on the image quality, this seemed more pronounced at longer focal lengths. So I don't use them and rely on the lens hood to protect the front elements from getting knocked.

thanks posty,that'll do me boy,you just saved me a few quid,

I remember when my then very young son put a liberal coating of jam all over the front of every lens I then owned and I was glad I had UV filters on them all as it meant I could just take the filters off and wash them which was the only way I could deal with the jam. Try that with the lens itself. :)

it's not enough to convince me to use filters, but I will be putting the jam on a higher shelf :D

As my most expensive lens is waterproof, it wouldn't be an issue for me, I'd run the whole lot under a tap. ;)

Like Peter, I used to use UV filters to protect the front element when I used film cameras. When I went to digital, I used the new lens without a filter fitted as I didn't have one of the right thread size. When I did then buy one, and fitted it, I realised just how much it was degrading the image. Took it of and haven't used them since.

The people in shops will tell you it's essential to have a UV filter to protect the front element. I rather think this advice is based on boosting sales of accessories.

From my experience filters degrade the image quite a lot on long telephotos whereas the same filter on a wide/normal lens does not seem to make that much effect. That's certainly what I have experienced with the 400/5.6 and 17-40/4 when using the same filter.

Any filter is going to degrade the image you get from your lens. It's just a question of weighing up to pros and cons of fitting filters and which one you use/ how much degredation you can stomach. I've been using B&W or none at all. Some lenses are worse than others when fitted with protective filters. My Sigma 15-30mm is simply (more) terrible with anything fitted (probably due to the poor filter ring/hood arrangement), Nikkor 80-200mm is passable......
One thing to mention about protective filters.... They do protect against other things not just rain. A lovely lens in the shop, looked after, except for a ruddy great scratch across the front element from suspected mud/grit. However, it never fails to amaze the number of top-notch Canon L and Nikon AF-S expensive glass seen with the cheapest Chinese filters screwed to the front!...So, I can see both sides of the 'for and against' can come into play.
I guess the key factor is to decide the as and when to use lens protection, rather than to fit and forget.

I have now got a Canon 300/2.8 so I no longer have to weigh up the pros and cons of a protective filter - you cannot fit one if you wanted to.