HoppyUK
Suspended / Banned
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- 23,200
- Name
- Richard
- Edit My Images
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I don't think there's any problem with all filters here Rob, just either low grade or perhaps faulty filters. Possibly bootleg copies and the like. I think you use Hoya Pro-1 don't you? Sorry if I've got that wrong but I have a Pro-1 UV and can't replicate the effect on my longest lens - 70-200 x1.4. It's sharp as you like, smooth bokeh, identical with and without the filter.
If I was working in the same conditions that you have described from time to time, or those you've mentioned above, I would use a protection filter too. Of course. In fact, that's why I've got one even though I've never used it so far - it's salt sea spray I'm wary of, horrible stuff.
PS Now I think about it, I've got a cheap n nasty old polariser that I know has sharpness issues - might do some with and without comparisons tomorrow if the sun shines. But I know before I start that it will be rubbish
Time for me to eat some humble pie I think, and apologies to Rob especially. Having now done a few tests, I don't think the OP's problem is a filter problem primarily, not the strange background bokeh effect anyway. I now believe it is primarily a characteristic of the 100-400L lens, made worse by the filter.
I tried to replicate a back-lit scene like the OP's, with sharp foregound and background with out of focus highlights, and shot it with my 5D2, 70-200L 4 IS and 1.4x Kenko Pro telecon = 280mm, which is the longest combo I've got.
I tried it without a filter, with a Hoya Pro-1 UV, and a cheap old uncoated polariser of known naff quality. It's not quite the same as the OP's situation, but if it was a straightforward long lens plus low grade filter thing, it would have shown up clearly enough. I shot at both f/5.6 (wide open) and f/11.
In terms of background bokeh, there was no difference between them.
The shots without a filter and with the Hoya Pro-1 were identical as far as I could see, as expected, but while the poor quality polariser pretty much destroyed fine detail sharpness, it had no discernable effect on the look of the out of focus background highlights.
On the sharpness aspect, I've tested that before and concluded that was caused more by a dodgy polarising layer than by the filter per se.
The conclusion for me is looking like this. The OP's problem is mainly an inherant lens issue, a charcteristic of the 100-400L. The filter certainly hasn't helped and there's quite possibly some heat haze going on too.
I'm also thinking that while filters don't do us any favours in terms of image quality as previously outlined, they are not always the cause of every image degradation problem. Sorry Rob
