question on download size dimensions

joejoejoejoe Registered Users Posts: 19 Big grins
edited October 24, 2008 in SmugMug Support
Hi,

Suppose my original image has dimensions of 3000 x 2000 pixels.

If I said 1 Mpix downloads would be about 1200 x 800 pixels and 4 Mpix downloads would be about 2450 x 1633 pixels, would I be correct?

If I'm wrong, what would the approximate size be for the 1 and 4 MPix downloads based on the original image size given?

For the future, how are the smaller sizes calculated anyway? If my originals were larger at some point, is there a calculation I can use to figure this out or do I just find dimensions which are proportional to the original and equal about 1 (or 4) megapixels?

Thanks

Comments

  • PBolchoverPBolchover Registered Users Posts: 909 Major grins
    edited October 24, 2008
    Your original photo has 3000x2000 = 6 million pixels.

    When you rescale to a smaller size, you multiply each of the Width and Height by the SQUARE ROOT of the size ratio.

    For example, 1-million pixel file has (1/6) the number of pixels. The Square root of 1/6 is 0.408. The new file would therefore by (3000x0.408) by (2000x0.408), ie 1224x816.

    A 2-million pixel file would be (3000 x sqrt(1/3) ) by (2000 x sqrt(1/3)) = 1732x1155
  • AndyAndy Registered Users Posts: 50,016 Major grins
    edited October 24, 2008
    http://www.smugmug.com/help/sell-digital-downloads

    To find out how many megapixels an image is, just multiply the pixel dimensions together and divide by 1 million. For example, an 816x1224 image is 998,784 pixels. Divide that by 1 million and you get .998784 (just under 1 Megapixel). If it is twice as wide and tall, or an 1632x2448 image, it will be nearly 4 Megapixels.
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