Theory Proved. Linear and DF AF . . .

Discussion in 'Beyond the Basics' started by Canon Fan, Jun 17, 2005.

  1. Canon Fan

    Canon Fan TPF Noob!

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    I took a chance and orderd a Linear Polarizer (by accident) for my new AF lens (Sigma 24-70mm EX f/2.8 DG-DF) and it does work GREAT! Even though the owners manual itself says to use a C-PL (Circular Polarizer).

    My theory was, that if, the front element does NOT rotate (which this one does not) why can't you ues a standard (MF only) Linear PL? Well . . .

    I had a couple cocktails one night and foolishly orderded the cheapest PL filter I could find for 82mm only to find the very next day that it was a linear and not a C-PL. OK I thought "What the Heck? I'll try it and if it doesn't work my theory will be junk and I'll just re-sell it" well it does seem to work thus far. Has the same qualities that I find in my much more expensive C-PL for other lenses (with rotating front element) but half the cost (granted that was more than paid for in the lens cost).

    I WILL post pics to prove this when I get a chance. In the meantime, please, any pro's or people in the past that have tried this tell me what problems I may find or that I am being dumb now! This was a VERY shallow test so far ( so I still could be proved wrong :( ) but so far we are all good, it delivers razor sharp focus and very good contrast in cloudy skies as well as zoomed reflections ;)





    Disclamer: A no rataing front element lens means that the very front of the lens does not ROTATE at ALL during autofocus operation.
     
  2. tr0gd0o0r

    tr0gd0o0r TPF Noob!

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    Just to make sure, are you using your autofocus during the test? Cuz I think that's where the problems are supposed to show up.
     
  3. SLOShooter

    SLOShooter TPF Noob!

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    It's the autofocus that USUALLY has the difficulties. Some of the newer autofocusing mechanisms use polarized light to do the focusing so obviously if you mess with the polarization of the incoming light they will have problems. That's not to say it WILL NOT work. Just that it may have some difficulties.
     
  4. BernieSC

    BernieSC TPF Noob!

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    I have tried linear polorizers on AF and sometimes if not most of the time it does work. Its just that there is a chance the linear lines that make up the filter can interfer with the focusing. Its not different from shooting through a fence or something with lines that can fool the AF. Sometimes it works sometimes it doesn't.
     
  5. Canon Fan

    Canon Fan TPF Noob!

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    Ya sorry for the brash wording I used for this post above :oops: It does seems to work. The AF does occassionally "hunt" a little bit more than usuall but it does seem to work OK.

    I guess mainly what I had before was a bit of a misunderstanding on just how AF actually works :er:
     

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