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  1. #11
    Join Date
    May 2009
    Posts
    19
    Very informative, Don. Thanks a lot. My knowledge had just increased 'by that much'. Now.....to digest all that.....

  2. #12
    Join Date
    Mar 2009
    Location
    San Diego, CA
    Posts
    602

    Question Lens coating and legacy lenses

    Quote Originally Posted by Peekayoh View Post
    Good post, Don.
    The only area where I would take issue is the reference to Digital Coatings.
    This is marketing speak designed to encourage people to replace their existing film lenses.
    If people were to pick up some of the old Konica/Minolta "film" lenses and experienced the chromatic aberations, is there any way to add a coating or filter to combat that effect?
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  3. #13
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,554
    Normally CA (chromatic aberration) is in the design of the lens. It is the way light gets through the glass medium at different wavelengths and winds up looking split on the sensor. Most high-end lenses take this very seriously and use elements (composed of fluorite) in them that have differing dispersion rates and when ASSEMBLED into a compound lens, realign the different colors into the same spot on the sensor.

    Name:  CA explanation.JPG
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    Now, you are going to have to explain to me HOW you can do that with a simple layer of optic juice, because I am having some difficulty seeing it.

    Purple fringing
    is similar to color aberration, but it takes place not at the sensor, but inside the "micro lenses" of the sensor itself. Green is correctly channeled through the lens, but red and blue are incorrectly focused and result in the purple color around highlights. Haven a good lens on the camera will reduce the effects of purple fringing, but the best remedy aside from construction of that "good lens", is the use of a demosaicing algorithm in the processing portion of the camera's output.

    In other words, we are in an area that requires quite a bit more thought than just a "coating." If only it were so easy to solve.
    Last edited by DonSchap; 06-14-2009 at 10:24 AM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  4. #14
    Join Date
    Nov 2008
    Location
    Monmouthshire, UK
    Posts
    2,152
    Quote Originally Posted by DWessel View Post
    If people were to pick up some of the old Konica/Minolta "film" lenses and experienced the chromatic aberations, is there any way to add a coating or filter to combat that effect?
    CA's are the result of poor lens design. Stands to reason that a cheap lens is likely to be worse than an expensive one.
    If you pick up a good Minolta lens, CA's will be well controlled and won't be a major issue.
    Plenty of new digital lenses are worse than some old Minolta glass.
    The good news anyway is that CA's are reatively easy to deal with in post processing.

  5. #15
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,554

    Cool See CA for what it is ... in your digital camera

    Okay ... in a nutshell, because a picture is worth a thousand words ...

    Here is the 100% crop of a TAMRON AF 70-300mm f/4-5.6 LD @ f/4.5 w/ a circular polarizer (a good one!) (the typical "branch against the bright sky" scenario)

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    And here is the reason you buy a TAMRON SP AF 70-200mm f/2.8 Di LD @ f/4.5 w/ a circular polarizer (a good one!)

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    As far as Chromatic Aberration goes, it really doesn't get much clearer than that, my friends.

    Now, the purple fringing can be cut down by tightening up your aperture, but then you change things like DOF and, of course, the amount of light the camera will see, creating a more silhouette effect.

    TAMRON AF 70-300mm f/4-5.6 LD[/SIZE] @ f/8 w/ a circular polarizer

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    TAMRON SP AF 70-200mm f/2.8 Di LD[/SIZE] @ f/8 w/ a circular polarizer

    Name:  70-200-f8-100-crop.jpg
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    Oops ... this went a little "Off Topic" ... good stuff, but let's get back to those crazy lens mount differentiations.
    Last edited by DonSchap; 06-14-2009 at 12:51 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  6. #16
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
    Posts
    9,554
    How about a lens mount "bump", for the new guys?
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  7. #17
    Join Date
    Jan 2008
    Location
    Ohio, USA.
    Posts
    1,161
    And how about a bump fpr Tokina, come on guys, A-mount!
    Sony A700_____________Minolta AF 50mm. F/1.7
    Minolta AF 70-210mm F/3.5-4.5 Tamron AF 17-50mm F/2.8 XR DiII LD Asp. [IF]
    Tamron SP AF 70-200mm. F/2.8 DI LD [IF] Macro
    Tamron AF 70-300mm F/4-5.6 Di LD Macro 1:2
    Tokina AF 28-70mm F/3.5-4.5
    Tokina AF AT-X 80-400mm F/4.5-5.6
    http://flickr.com/

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