polarized filter issue

[lowpine]

Yeah, that looks like it is the filter unless there was some sort of gross focus error.

Can I ask one favor, if you end up deciding to throw away this filter please send it to me instead - I'm curious and will pay shipping!
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Ken W
See plan in profile for equipment list

pm sent

 

[Midnighter]

Well if you do, tripod mount it with the sun off at 45+ degrees to the camera, then hold the filter half off the lens and take four shots quarter rotating the filter for each shot. You should end up with light showing polarisation in a couple of shots and not in others. If you see the polarised section of the image degrade under polarisation ya discovered some spooky stuff going on, which means either the AA filter or the microlenses are reacting to the polarised light. Pretty much no chance of that though.

 

[Bobo Hodls]

I think a more conclusive shot would be one that's closer to what you'd consider a "keeper, something that had acceptable sharpness. As in: sample "A" with the filter is unacceptably fuzzy, sample "B" without the filter is acceptably sharp.

Yes, the shots without the filter look sharper but none of the shots look sharp. They're all hazy and lack contrast, with or without the filter. Perhaps ther's a lens flare thing going on or something. So I think this is not a conclusive test unless you're trying to figure out the best technique for shots that are going to come out hazy anyway.

Are these shots cropped?

not cropped.

It was noon hour with overhead light, a bit of a hazy day to begin with, then I shot over the river. This wasn't an exercise in composition or getting the sharpest image, just trying to determine if the polarized filter is causing the blur at long focal lengths.

OK, what would be a conclusive test then? I'm satisfied that the filter is no good over 100mm, at shorter focal lengths it's OK but I don't have high expectations.

both A and B have the polarized filter, C and D don't......

I didn't look at the originals of the 2nd batch, but offhand I wasn't convinced either that there wasn't still some user error at play. Why? I never experienced this, only UV filter softness on telephotos. But if it occurs with UV glass, why not with polarized glass then? Ken and others of more experience have seen it before, no problem making that call. But the unconvinced aren't (necessarily) dense or dim, and would like to have it make sense (without seeing it personally).

So I defer to the experienced in the matter. And then. . .

I recall what I thought was a great study with a good telephoto lens on details of a waterfall. Using a Singh-Ray Variable ND, later the results were seen to be very soft (not quite as soft as what's in this topic). Not a problem from being a cheap filter, and I could swear my focus was precise. I called Singh-Ray, who shrugged and suggested I send it in. I never did, and being I didn't use the filter much in that manner in the back of my mind I thought it was user error.

I learn something every day. (and it's always nice when that's not, "I should have stayed in bed.")

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...Bob, NYC
http://www.bobtullis.com

"Well, sometimes the magic works. . . Sometimes, it doesn't." - Little Big Man
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