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Magnification, sensor size and crop factor 25 Disember 2009

Posted by azmirul in Astrophotography, Photography.
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setelah study dibuat, akhirnya berjaya juga aku memahami secara “kasar” macamner nak calculate magnification power bila guna webcam/camera bersama telescope. rupa2nya semuanya amat bergantung kpd sensor size yg akan menentukan crop factor dgn perbandingan dibuat berdasarkan format film 35mm.. patutler field of view (FOV) bila guna webcam semakin kecil berbanding bila guna DSLR.. ini disebabkan sensor webcam yg amat kecil iaitu dlm 4mm diagonal (utk SPC900NC) berbanding DSLR iaitu 26.7mm diagonal (EOS 350D).  So, utk full frame sensor yg hampir sama dgn standard film 35mm (43.3mm diagonal) akan memberikan FOV yg lebih besar. So, ada kemungkinan wide-angle lens utk 35mm camera menjadi normal lens utk DSLR camera!

Berikut adalah beberapa calculation yg aku buat.. ni berdasarkan apa yg fahamler.. kalo tak tepatpun, aku raser masih bleh digunakan utk buat perbandingan.

Magnifaction of Telescope Apex 90mm with Philips SPC900NC Webcam:

  • crop factor for Philips SPC900NC is 10.8
    ( 35mm diagonal/sensor diagonal = 43.3/4 = 10.8 )
  • 35mm equivalent telescope focal length when using spc900nc
    ( 1250mm focal length * 10.8 = 13500mm )
  • magnification calculation (divide by 50mm) is 270x
    ( 13500mm/50mm = 270x  )

Magnifaction of Telescope Apex 90mm with DSLR Canon EOS 350D:

  • crop factor for Canon APS-C sensor is 1.6
    ( 43.3/26.7 = 1.6 )
  • 35mm equivalent telescope focal length when using Canon EOS 350D
    ( 1250mm focal length * 1.6 = 2000mm )
  • magnification calculation (divide by 50mm) is 40x
    ( 2000mm/50mm = 40x )

Common crop factor:

  • 35mm film = Diagonal (43.3mm) = 36 x 24 mm ( Crop factor 1 ), 3:2 aspect ratio
  • DSLR with Canon APS-C sensor = Diagonal (26.7) = 22.2 x 14.8 mm ( Crop factor 1.6), 3:2 aspect ratio
    eg crop factor calculation = 43.3/26.7 = 1.6
  • Typical compact digital camera = 1/2.5″= 5.76 x 4.29 mm ( Crop factor 6.02 ), 4:3 aspect ratio
  • Common camera phone/ webcams/ digital camcorders = 1/6″ = 2.40 x 1.80 mm ( Crop factor 14.14 )
  • SPC900NC webcam = 35mm diagonal/webcam sensor diagonal = 43.3/4 ( Crop factor 10.8)

Reference: (selanjutnya…)

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