An entire expedition's photos ruined by a pol filter
Moderators: rjlittlefield, ChrisR, Chris S., Pau
An entire expedition's photos ruined by a pol filter
I've just come back a few days ago from a fantastic five-day trip to a remote area in Ecuador. I found several plant species important to my work, including two recently-described species of magnolia trees. I made lots of automatic focus-bracketed stacks of these plants using my Oly PEN F and 60mm macro lens. I did not have time to run the stacks through Zerene during the trip.
Now that I am back, I find all my stacks are garbage, with weird angular patterns and strong astigmatism in all highlights. It is heartbreaking. What could have gone wrong? I had done this hundreds of times before, with excellent results.
I had a Bower circular polarizer on the lens at almost all times, in case it would be useful. It turns out that this filter is what ruined the stacks. I just ran some test stacks, and there was no problem when the polarizer was removed, or when a different polarizer (B+W) was used, but they were ruined by the Bower polarizer.
Left: 200% no pol, middle 200% Bower pol, right 200% B+W pol:
Now that I am back, I find all my stacks are garbage, with weird angular patterns and strong astigmatism in all highlights. It is heartbreaking. What could have gone wrong? I had done this hundreds of times before, with excellent results.
I had a Bower circular polarizer on the lens at almost all times, in case it would be useful. It turns out that this filter is what ruined the stacks. I just ran some test stacks, and there was no problem when the polarizer was removed, or when a different polarizer (B+W) was used, but they were ruined by the Bower polarizer.
Left: 200% no pol, middle 200% Bower pol, right 200% B+W pol:
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- rjlittlefield
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Rik, I don't see any ripples while looking at the reflections on the filter.
Antal, here are 200% crops of two single shots through the polarizer, one focused closer than the slice of best focus, and the other focused farther than the slice of best focus. You can see that the out-of-focus highlights of the two slices form sharp lines, in perpendicular directions from one slice to the other. These streaks, being relatively sharp, appear in the final stack, forming crosses everywhere.
Antal, here are 200% crops of two single shots through the polarizer, one focused closer than the slice of best focus, and the other focused farther than the slice of best focus. You can see that the out-of-focus highlights of the two slices form sharp lines, in perpendicular directions from one slice to the other. These streaks, being relatively sharp, appear in the final stack, forming crosses everywhere.
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joeD, the B+W polarizer has the following text inscribed on the front of the ring: "B+W 52 KSM HTC-POL MRC". On the outside of the ring it says "F PRO". "B+W", "MADE IN WEST GERMANY".
By the way, this is what the very distinctive false-detail cross-hatched astigmatism artifacts looked like in my stacks. here shown at 200%. On the real object there are no linear features whatsoever.
By the way, this is what the very distinctive false-detail cross-hatched astigmatism artifacts looked like in my stacks. here shown at 200%. On the real object there are no linear features whatsoever.
a bit off topic:
but I noticed you complained you did not have time to check your stacks during the trip:
Speaking about PROCESSING TIME.
I found the current version of Helicon is significantly faster than Zerene at processing JPG.
Let’s say Helicon is 3 minutes faster with a particular set of frames.
That’s irrelevant. 3 minutes is nothing, it's not enough to make a coffee….
But, when I come home, after a morning out, and I have 20 bracketed sequences and 2.500 photos to stack… 60 minutes (3*20) is very significant time…
So I bought the most basic and cheap license of Helicon.. 1 year for like 30 USD, if I remember well, only to “quick preview” the stacks.. and I just work with Zerene the sequences who are worthy to turn into final images.
Antonio
but I noticed you complained you did not have time to check your stacks during the trip:
Speaking about PROCESSING TIME.
I found the current version of Helicon is significantly faster than Zerene at processing JPG.
Let’s say Helicon is 3 minutes faster with a particular set of frames.
That’s irrelevant. 3 minutes is nothing, it's not enough to make a coffee….
But, when I come home, after a morning out, and I have 20 bracketed sequences and 2.500 photos to stack… 60 minutes (3*20) is very significant time…
So I bought the most basic and cheap license of Helicon.. 1 year for like 30 USD, if I remember well, only to “quick preview” the stacks.. and I just work with Zerene the sequences who are worthy to turn into final images.
Antonio
Lou,
Do the astigmatism crosses show across all the frame or only at the periphery?
I ask it because I have the same issue with the AZ 100 objectives although only at the periphery. I'm blaming the objectives although now I also can suspect of the EO optical window placed in front of it to compensate spherical aberration (they are designed to see through a quarter wave plate or plain window)
Do the astigmatism crosses show across all the frame or only at the periphery?
I ask it because I have the same issue with the AZ 100 objectives although only at the periphery. I'm blaming the objectives although now I also can suspect of the EO optical window placed in front of it to compensate spherical aberration (they are designed to see through a quarter wave plate or plain window)
Pau