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When Does 8MP equal 6MP?

Discussion in 'Smartphone photography' started by Roy5051, Oct 16, 2017.

  1. Roy5051

    Roy5051 Well-Known Member

    I have a Motorola Moto E3 (3rd Gen) mobile phone, which boasts an 8 MP rear camera and a 5 MP front camera.

    When I take a photo on the rear camera, it comes up as 6 MP and the front camera at 5 MP. Anybody any idea why this should be? Perhaps using the zoom reduces the megapixel count, though I do not really know why? The phone is set to its highest resolution, so surely I should be seeing 8/5 megapixels? Pixel count for the rear camera is 3840 x 1840

    Last edited: Oct 16, 2017
  2. PeteRob

    PeteRob Well-Known Member

    well that's 4.325 MP
  3. Roy5051

    Roy5051 Well-Known Member

    Sorry, I had cropped that one, true resolution now on original post.
  4. RogerMac

    RogerMac Well-Known Member

    I make it 7,065,600 pixels
  5. Roger Hicks

    Roger Hicks Well-Known Member

    Rounding error.

    Mind you, if the discrepancy were greater, it could be a squaring error.

    Thought: perhaps it's the difference between total pixels on array and usable pixels on the image area? Multiplied, perhaps, by the MTF, which in this case stands for Marketing Transfer Function?

  6. PeteRob

    PeteRob Well-Known Member

    well thats 6.738 MP
  7. RogerMac

    RogerMac Well-Known Member

    Sorry but I still think 3840 x 1840 equals 7,065,600
  8. Roger Hicks

    Roger Hicks Well-Known Member

    Dear Roger,

    My calculator agrees. I hadn't even bothered to check the original sum, even mentally, because it's so hard to get it wrong if you bother to try at all.

    Maybe Heraclitus had it in for the original calculation?


    RogerMac likes this.
  9. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    7,065,600 pixels is 6,900 MP if you use kilobytes instead of 1,000s. Still doesn't match either the claim or the report. I think I'll go with Roger's "Marketing Transfer Function".
    RogerMac likes this.
  10. PeteRob

    PeteRob Well-Known Member

    It does - I was dividing by 1024 x 1024 for MBytes - which was wrong.

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