HELP ME: How to crop an image using a crop factor?

Discussion in 'Open Discussion' started by Kenny, May 31, 2013.

  1. Kenny

    Kenny Mu-43 Regular

    Sep 9, 2012
    KL Malaysia
    Im planning to buy a blackmagic pocket cinema camera in the future. It has 1.3 crop factor over MFT sensor. Can someone teach me how to crop a 7mm focal length image (from 7-14mm lens) using 1.3 crop factor??? I dont have this lens, but Im sure we can "borrow" someone image and crop it :biggrin:
    I have Photoshop software on windows 8. thanks in advance :2thumbs:
  2. Crdome

    Crdome Mu-43 Hall of Famer Subscribing Member

    Sep 11, 2011
    West Central Indiana
    Just slap on the lens and shoot. There is no magic or post processing needed. The crop factor is the amount image cast by the lens that is larger than the sensor. From a Blackmagic add it is billed as a "Super 16", which is somewhat smaller than the MFT sensor so any MFT lens will cover the sensor with room to spare. My "Super 16" lens vignettes below the 35mm FL on the MFT. In theory it would fully cover the Blackmagic sensor.
  3. Cruzan80

    Cruzan80 Mu-43 All-Pro

    Aug 23, 2012
    Denver, Co
    Sean Rastsmith
    I think he is wanting to know what the picture would look like if he mounted it on the BlackMagic sensor.
  4. Kenny

    Kenny Mu-43 Regular

    Sep 9, 2012
    KL Malaysia
    Exactly! I want to see the widest fov the pocket can go with 7-14mm at 7mm.

    Sent from my GT-N7100 using Mu-43 mobile app
  5. sLorenzi

    sLorenzi Mu-43 Top Veteran

    Sep 15, 2010
    If I understood it right, you'll have a 20,16mm in 35mm equivalent terms.

    here is a simulation: Abelcine
  6. Kenny

    Kenny Mu-43 Regular

    Sep 9, 2012
    KL Malaysia
    Thanks but, is there any direct cropping that I can apply to any 7mm image from mft sensor? I know this should be simple, but I just cant figure it out. Keep in mind that this is between mft sensor and pocket cinema sensor.
  7. flash

    flash Mu-43 Hall of Famer

    Apr 29, 2010
    1 hour from Sydney Australia.
    At 7mm it'll be the same field of view as a 9.1mm setting on m4/3 which in turn is about the same as 18.2mm on a 35mm camera.

  8. DHart

    DHart Mu-43 Hall of Famer

    Jan 7, 2010
    Scottsdale, Arizona
    I think this would work... an approximation would be to determine the diagonal image size dimension reduced by 70% or so. I would measure the corner to corner (diagonal) length of the m4/3 image, take 70% of that number, then measure the horizontal base of the image and use those numbers with this online calculator to determine your other measurements:

    Right Triangle Trig Calculator

    Then use your crop tool in Photoshop with the new measurements. Won't be perfectly exact, but give an approximation.

    Using this method gives me this approximation for a 1.3 crop factor. ('51 Chevy I just sold... I miss it already!)
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