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Thread: Quick extension tube question

  1. #1
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    Quick extension tube question

    Hello! I just acquired a HC 120 f4 macro lens, and already have a 52mm extension tube.. I am just curious if anyone knows, or how I could find out what the magnification factor of that combination is...


    Thanks in advance

    test shot and 100% crop to the right of Mr. Lincoln's ear.

    Rick Rose
    www.RickrPhoto.com
    HasselPhase

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    Re: Quick extension tube question

    1. Measure the diameter of your penny (in mm). (You can save a bit of time by shooting a mm scale or ruler.)

    2. Measure the number of pixels across the image of the penny is.

    3. Multiply the number of pixels by the pixel pitch in mm. That will give you the image size. To convert um (mircons or micrometers) into mm, divide your number by 1,000

    4. Finally, simply divide the image size by the object size. That is the linear magnification at the image plane or sensor. (BTW, if you make a print, that magnification will then change as the image is larger--that is the reason scientists use scale bars rather than describing magnification.)

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    Re: Quick extension tube question

    BTW, if you have Photoshop Extended, there are measuring tools that make this easy. You can also measure area.

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    Re: Quick extension tube question


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