Sigma 77mm UV filter for Canon's 100-400mm L lens

I'm thinking of buying Sigma's 77mm UV filter for Canon's 100-400mm L lens. I've couple of questions.

1. Has anybody used the Sigma filters & found them good ?
2. I know there's lot of threads on this lens' behavior at 400mm as being little soft at F5.6. Would the picture quality drastically decrease as to not to have a UV filter at all?

Let me know your thoughts

Regards
Gautham

G: I shoot the 100-400L a lot. I never shot the Sigma UV filter, but have shot extensively with the Hoya circular polarizer and Hoya UV filters on that lens. Neither ever degraded image quality that I could see.

Very doubtful they will degrade image quality because they are "poor" quality. Filters are so close to the lens that it focusses right through them.

My thinking on UV filters has evolved over the years. When I started, I bought one because the guy selling the camera said they would "protect my lens." Over the years I came to see them as a nuisance and they never seemed to do anything for me at all. Then I got into railroad photography--taking photos of trains. The bright headlights would hit the filter and cause major ghosting and flare. So, I get rid of the UV filters and that eliminated the problem. I often DO use a polarizer, when it will help a scene (maybe 70% of my daytime shots?) To get around the flare/ghosting problem I now only buy & use multicoated filters. Since I started using those a couple of years ago, I've noticed that the uncoated filters actually were causing me problems--I just didn't realize it. When shooting into the sun or other bright light (train headlilghts! ) the color saturation was decreased. The uncoated filters can cause problems because there is more light bouncing around. So, I use coated filters, but only use them when I have a NEED for them.

A UV filter really seems to have no UV-reduction effect on an image that I can tell. So, why use one? Ah yes, the old "protect your lens" theory. I've come to think there are times this is valid, such as shooting around a misty waterfall. (The mist contains fine grit I truly DON'T want on my lens!) Of course, I use a polarizer around waterfalls anyway, not a UV. There are other shots I take in extreme dusty conditions and then will use a UV to cover the lens. And that's about it. I do NOT keep a filter on just to have it on. As for "protect the lens," last month my Nikon 80-400mm VR blew over and landed "face" down on a hillside. The $125 polarizer did not protect the lens. It smashed, and broken glass then scratched my lens. Turns out the filter is $125 and the front lens element can be replaced for $100. Wow, that's the way to buy protection! There is something I do use 100% to protect the lens--the lens hood. Well, almost 100%. If I had the hood on, I think my $125 filter and $100 front element would have been OK. The lens hood also fights flare.

So, my advice is, buy the Sigma UV filter only if it's multicoated. If not, it can cause you problems with flare. Use it to keep blowing snow, dust, waterfall spray off your lens but only when photo'ing in those conditions. And take it off when you use a polarizer. I'm trying to remember the last time I used a UV filter, and I just can't. Maybe it was last fall when I was up inside a dusty grain elevator taking photos of loading trains?


Kent in SD

Hi Kent
Thanks for that wonderful reply. Having read all the posts related to filters, I seem to concur on that thought that "use only in dusty conditions" if required, else lens hood is sufficient.

Thanks & regards
Gautham

Like Kent, my use of UV filters has changed. I started with one on at all times as lens protection, but my hood's on all the time, too, and I haven't put on a UV lens for over a year.