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  1. R

    Can anyone explain the physics of an auxiliary telephoto / teleconverter lens?

    An auxiliary telephoto lens that attaches to the front of a lens can use a variety of groups/lenses. Some use 2 groups with 4 lenses, some use 3 groups with 5 etc. I'm unsure how it exactly works and i'm looking for somewhere to learn. Is there anyone that can explain how the optics work and...
    • redrose_45
    • Thread
    • focal point groups optics physics teleconverter telephoto vignetting
    • Replies: 4
    • Forum: Talk Photography
  2. stephen melia

    Best lenses for wedding on crop sensors from list below

    Cannon EF 70-200mm f2.8 L is usm II Cannon EF 70-200mm F4L USM , Cannon EF 24-105 F4L IS , Cannon EF85mm f1,8 usm , Sigma 10-20mm f4-5.6 EX DC HSM , Cannon EF 100mm Macro usm, Cannon EFS 55-250mm is, Cannon EFS 18-55MM
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