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10X Fooled

Friends, one of the main parameters we look at when buying a digital camera is the number of “X” optical zooms.  Isn’t it?  I recently learned a hard truth.  We have been FOOLED by the marketing strategy, so far!!!
We all have learned in high school physics that image magnification is based on the focal length of the lens.  Nothing has changed from that.  All the lens have focal length written on the side like 18mm-55mm, or 50mm-80mm etc (even for point & shoot camera).  So, in camera world the X calculation is,

X =  (maximum focal length – minimum focal length) / minimal focal length;

ie., for 18mm-55mm lens,

X = (55 – 18) / 18  = 2 (approx)

Nikon 18mm - 55mm DX lens

If so, for a 600mm-600mm lens, X = 1; isn’t it?  So, does it mean it is not providing any magnification?

Nikon 600mm lens

The camera manufacturers has changed the whole theory and have their own way of representing a attractive “X” values, especially for point and shoot camera.  Are it you curious to know what these guys mean?  For that we have to know focal length equivalence factor.  This number is based on the lens each camera brand uses, and in turn means they define it themselves.

So, Maximum focal length = Magnification factor (X number) * focal length equivalence

Now we have to find the focal length equivalence for the camera.  Many popular brands follow either 28mm or 35mm focal length.  For writing this blog I was going through few point & shoot camera specifications.  Found that Nikon and Canon camera specs have this focal length equivalence number on somewhere easily missable part of their specs within a bracket.  Other brands like Olympus doesn’t care to publish this info on the specs.

Nevertheless, now you know how to find that with X value and Maximum focal length (found on lens side).  Don’t go by just X value.  Next time I will try to come up with some truth about MP (Mega pixel).

Categories: Photography
  1. mithran
    March 4, 2011 at 5:52 pm

    வேற எந்த blog பார்த்தும்
    அண்ணன் இப்படி off ஆனதில்லை

    “நான் தல காலு புரியாம
    தரை மேல நிக்காம
    தடுமாறி போன்னேனே”

    இது அரியர் வெச்சு தான்
    படிக்கணும்னு நினைக்கறேன்.ம்ம்!!!
    படிக்கறேன்.. because
    “விடா முயற்சி விஸ்வரூப வெற்றி!”

  2. March 17, 2011 at 1:46 pm

    புரியுது ஆனா புரியாத மாதிரியும் இருக்கு.
    ஸ்ஸ்ஸ்ஸ்ஸ்ஸ் இப்பவே கண்ண கட்டுதே

  3. March 17, 2011 at 7:11 pm

    Hi Arun,
    It was a nice informative write up. Please keep up the work and share your knowledge.

    • Arun Velusamy
      March 18, 2011 at 11:36 pm

      yenna da venkat, thideernu ulta comment adikara?

  4. Raj
    January 23, 2012 at 8:18 am

    Arun, Quite informative, keep writing

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