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DPChallenge Forums >> Hardware and Software >> Polarizer with 100-400L trouble
Showing posts 1 - 7 of 7, (reverse)
12/19/2017 01:20:59 PM · #1
I'm sure I've shot with my 100-400 with a polarizer before without trouble, but I have a new circular polarizer and a new body (the mark IV) since the last time I did it. The images are not focused when I shoot at the long end. I've tried on both Av and Tv. The scene is about as bright as you are going to ever get (Oceanside at midday). What gives? Could the polarizer be the difference? This one isn't expensive, but does come with a money back guarantee and I wonder if I should do that when I get home (currently in Costa Rica). Lens works fine without the polarizer.
12/19/2017 01:39:53 PM · #2
I haven't shot with a polarizer for a long time, but I don't remember there being an issue with it and the 100-400L...
12/19/2017 01:41:14 PM · #3
Polarizer could very well be the difference. It's probably not affecting focus, rather the glass is probably not completely flat and is introducing optical aberrations that show up more visibly at longer focal lengths. The resolution of the 5D IV is already pushing the available resolution of the original 100-400.

ETA: a polarizer is like stacking two normal filters, since there are two separate pieces of glass. It's therefore especially important that the glass elements are both flat and parallel.

Message edited by author 2017-12-19 13:42:45.
12/19/2017 03:05:02 PM · #4
What Kirbic said. Your issue is almost certainly with the particular polarizer itself. On a lens that long and expensive I'd use nothing but the highest-quality polarizer, or no polarizer at all. You get what you pay for. And it's MUCH more difficult to manufacture a polarizer to high tolerances the larger the diameter is. With 77mm you NEED an excellent polarizer OR a low threshold of satisfaction -
12/20/2017 08:24:07 AM · #5
Thanks. I'll send it back when I get home. I haven't tried it on my sorter lenses, maybe it will do for those.
12/20/2017 09:52:37 PM · #6
What brand and model of polarizer?
12/23/2017 03:20:45 PM · #7
I highly recommend Breakthrough Photography's CPLs, UVs, NDs and their 100 mm filter holder. Like the OP, I have ruined a great lens with a cheap ass Polarizer. Breakthrough's are the only ones I use. And, they have a 25 year warranty.
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