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Conversation Between goldenarrow and IOO
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  1. IOO
    10-10-18
    IOO
    Hi
    I read your review on the HD Pentax-D FA 28-105mm F3.5-5.6 ED DC WR.


    This is a lens for full frame, and on K3 you have a smaller sensor, so you must multiply with 1,5. So on APC it is a 52,5-202,5 lens compared to what the same lens on full frame have to be.


    When Pentax on their lenses for the big 67 film cameraes (60x70mm large filmframe) write that the lens is 200 mm, that means it will be a 200 mm on a camera with a sensor 24x36 mm, Here you have to dived 200 with 70:36=1,944. So the 200mm on 67 gives you about the same area it covers as a 100 mm does on 24X36 (old film/FF).


    All lenses refers to the focal lenght on the old film size (so caled FF). Also lenses built for smaler sensors like the Q system. The 8,5 mm is copared to FF, on the first Q it's the same as 47,6 is on FF, on the later (wich has larger sensor) the same as 39,1on FF.

    Read this: Crop factor - Wikipedia


    Best regards IOO


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