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Thread: Lens ranges: why not CM, but MM ???

  1. #1

    Default Lens ranges: why not CM, but MM ???

    hey i got this kinda stupid qns in my mind for quite a long time ... normally we would describe lens range as 18mm, 35mm, 200mm, 600mm, etc etc ... but y dun we say like 1.8cm, 3.5cm, 20cm, 60cm, etc???

    hope someone would satisfy my curosity though ...

  2. #2
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    Ha ha ha ha ha....... Sorry, I had a LOL......

    But seriously, I would think that whoever was first started working with the figures find the useful significant figures to be at the mm level, so as to avoid using decimal points.

    What's the view of others.

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    i did a google search on the topic. Every kinda agreed that mm is the traditional unit of measurement for focal length. Nobody explained why. It probably goes way back to early 1900s when photography started, but i'm just guessing here.

    Anyone got a good link on this?

  4. #4

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    Early lenses were marked in cm (see the early nikkors). frisky's probably right here, avoids the use of decimel points.

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    Quote Originally Posted by ST1100
    i did a google search on the topic. Every kinda agreed that mm is the traditional unit of measurement for focal length. Nobody explained why. It probably goes way back to early 1900s when photography started, but i'm just guessing here.

    Anyone got a good link on this?
    back then metric system not the norm though...

  6. #6

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    Its probably because in the metric system you mostly work in powers of 1000. So: mm->m->km Its rather unnatural in scientific areas to work in cm.

  7. #7

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    oh ic ic ....

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