"Digital" CPL filters

Discussion in 'Photography Beginners' Forum' started by crisgil24, Sep 6, 2016.

  1. crisgil24

    crisgil24 TPF Noob!

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    I'm a SLR user and I'm looking into CPL's and I'm wondering if there's any difference between a labeled "Digital CPL" and just a plain non labeled one?


     
  2. tirediron

    tirediron Watch the Birdy! Staff Member Supporting Member

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    Probably about $10. Seriously, the use of the word "digital" is nothing more than a marketing ploy. If you're buying a filter, especially a CPL, make sure you spend a little extra and get a good one. Lee, Singh-Ray, B+W and Heliopan are the best names. Hoya, Tiffen and Cokin are decent, consumer brands.
     
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  3. fmw

    fmw No longer a newbie, moving up!

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    It took a while to understand what a CPL is. No there is no difference between two circular polarizers because one is labeled digital. There can be a difference in quality, of course, but the term digital wouldn't describe that. It would be a marketing term used to attract digital photographers.
     
  4. petrochemist

    petrochemist No longer a newbie, moving up!

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    I think I remember reading some marketing bumf on filters that claimed their 'digital' ones had improved coatings.
    Certainly I've never noticed any issues using older CPLs.
     
  5. pgriz

    pgriz Been spending a lot of time on here!

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    You have to pay for the "digital" one with digital currency.

    Joking aside, there was a difference between polarizing filters in that some were linearly polarized, and some were circularly polarized. The linearly-polarized ones didn't work well with auto-focus systems. As far as I know, pretty much all polarized filters are now of the circularly-polarized variety.

    As for marketing terms, I'm waiting for them to say they are gluten-free, zero fat, and carb-free. Heck, while we're at it, how about "assembled by organically-fed workers"?
     
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  6. KmH

    KmH Helping photographers learn to fish Supporting Member

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    SLR's that don't have auto focus (AF) or through-the-lens (TTL) metering can use a single glass element linear polarizing filter.

    SLR's & DSLRs that do have auto focus and/or through-the-lens metering require a circular polarizing filter.

    A CPL has a single glass element linear polarizing filter, and a 2nd, adjustable glass element that in effect blocks linearly polarized light so the AF and TTL systems in the cameras can function properly.

    So you can use a linear polarizing filter on a DSLR camera as long as you don't care that you have to manual focus and meter the light .
     
    Last edited: Sep 6, 2016
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  7. Solarflare

    Solarflare No longer a newbie, moving up!

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    Glas is never ever digital, but yes you need circular polarization filters.
     
  8. TCampbell

    TCampbell Been spending a lot of time on here!

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    CPL or referring to it as a "digital" polarizer may be referring to the auto-focus and metering issue.

    With a manually focused and metered camera, you can use a "linear polarizer" (sometimes called a "top polarizer").

    With a camera that uses phase-detect auto-focus and has built-in metering, a standard linear polarizer can make it extremely difficult for the focus or metering to work correctly.

    These cameras require something called a "Circular polarizer" (CPL). The circular polarizer is really just a dual layer filter... one layer has the standard linear polarizer just like any other linear polarizer, but it adds a second layer called a quarter-wave plate which alters the polarity of the lightwaves into a circular pattern (hence the name "circular polarizer"). This added layer (the quarter-wave plate) allows the auto-focus and metering to function as desired.

    Other than making sure you actually do have a circular polarizer, it's nice if it has anti-reflective coatings to reduce ghosting (reflections).
     
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  9. table1349

    table1349 Been spending a lot of time on here!

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    The only thing that I have ever heard that makes a "Digital" CPL different from a CPL is that the "Digital" Model does not have a UV haze layer in the coatings. Not sure if it true and frankly it doesn't really matter.
     
  10. unpopular

    unpopular Been spending a lot of time on here!

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    My digital CPL had this cool blue-yellow color shift as you rotated it! Added that highly sought after unpredictable pizzaz to my photography.
     
  11. TCampbell

    TCampbell Been spending a lot of time on here!

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    Any CPL should create a gold/violet color shift if you look through it "backwards". There is actually a real front vs. back on these filters and what happens to the light is different depending on which direction it passes through.
     
  12. unpopular

    unpopular Been spending a lot of time on here!

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    No way! So they installed the filter incorrectly at the factory?!
     

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