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Can cross-polarization be achieved with two linearly polarized (flash) lamps; one either side of a circularly polarized lens?

Lens attachments tend to be circularly polarized, while the PVA sheets available online tend to be linearly polarized.

I'm trying to tame some surface reflections and I'd like to know before I get my hopes up and invest too much time & effort into trying to fit a square peg in a round hole.

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Yes. Both of these filters exclude light that doesn't match the appropriate direction of polarization. Circular polarizing filters start with a linear polarization filter. They then also have a quarter-wave plate which transforms the light which has got past the filter so that it doesn't mess up autofocus and metering systems.

There's more on the background of how circular polarizers work What is the difference between a linear and a circular polarizer?, but for the purposes of this question, the basic answer is don't worry about it.

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  • \$\begingroup\$ How sure are you about that? \$\endgroup\$
    – voices
    Commented Feb 2, 2018 at 3:41
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    \$\begingroup\$ @tjt263u Completely. \$\endgroup\$
    – mattdm
    Commented Feb 2, 2018 at 3:47
  • \$\begingroup\$ Just came across this video on YouTube: youtu.be/ycY2mUZHS84?t=1m47ss Is this guy wrong? I mean; he is wearing a lab coat.. \$\endgroup\$
    – voices
    Commented Feb 2, 2018 at 4:03
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    \$\begingroup\$ That guy's not wrong. But it still doesn't matter, because the important thing is that the polarized light you want to exclude in order to reduce surface reflections will indeed be excluded. It doesn't matter that the the polarization is transformed after that. \$\endgroup\$
    – mattdm
    Commented Feb 2, 2018 at 15:04
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    \$\begingroup\$ Actually, he is at least a bit misleading with the way he says some things. For a more precise explanation of what he is addressing, please see this youTube video \$\endgroup\$
    – Michael C
    Commented Feb 3, 2018 at 0:14

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