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size matters

Discussion in 'Help Team' started by DJ72, Apr 21, 2017.

  1. DJ72

    DJ72 Member

    Hello Experts.
    I own a Canon G9x, and recerntly went travelling and took some cook pictures that I would love to make available to a wider audience.

    I was looking at alamy.com and the quality control states that each picture submitted "must be 17MB in size or more".

    With my Canon, even when shooting in AV mode, it doesn't create anything like that - most images are around 4-7MB in size (though the "resolution size" is often more than alamy.com's minimum requirement).

    So, is my interpretation of "size" correct? (that my image size must be min of 17MB), or is it the resolution size? I would ask Alamy forums myself but I am not yet a contributer.

    Assuming that my pictures dont qualify for alamy, what is the best way to make sure they do in the future? Shooting in raw is something I just started doing. The file size are always more than 17MB. Though after exporting them to JPEG they are all back down to 2MB or 3MB - so I feel like I am back to where I started!

    Sorry for the multiple questions wrapped up in one thread - I feel like they are related however.
  2. PeteRob

    PeteRob Well-Known Member

    The files on disk are compressed for storage. The opened image files may be larger and the size is roughly the number of horizontal x vertical pixels used.
  3. DJ72

    DJ72 Member

    Thank you for that ....so by my reading of "size" I should be doing what? Is the best way to copy them onto disk then open them (with Lightroom?) to see their true size?

    Or is there a specific calculation that I can use? Something like this:

    Step 1: Multiply the detectors number of horizontal pixels by the number of vertical pixels to get the total number of pixels of the detector.

    Step 2: Multiply total number of pixels by the bit depth of the detector (16 bit, 14 bit etc.) to get the total number of bits of data.

    Step 3: Dividing the total number of bits by 8 equals the file size in bytes.

    Step 4: Divide the number of bytes by 1024 to get the file size in kilobytes. Divide by 1024 again and get the file size in megabytes.
  4. Roger_Provins

    Roger_Provins Well-Known Member

    The specification says 5472 x 3648 (20.0 MP, 3:2) so that should just be okay BUT Alamy says "from a DSLR (or equivalent) camera". Is the Canon G9x equivalent to a DSLR?
  5. Andrew Flannigan

    Andrew Flannigan Well-Known Member

    It says quite clearly under "Guidelines for submitting images to Alamy", subsection "Technical Criteria"...

  6. DJ72

    DJ72 Member

    Thank you Roger, thank you Andrew. Yes, it was the uncompressed detail that I missed (and as I am in JPEG, then that would be the compressed version I am looking at.
    Just trying to open one of them in Lightroom to find out the true uncompressed size
  7. DJ72

    DJ72 Member

    Ah, and I find that I cant check for that in Lightroom....any ideas from anyone on how to check this? (I dont have Photoshop).
  8. PeteRob

    PeteRob Well-Known Member

    Probably multiply by 3 as there will be (R,G,B) for each pixel.
  9. PeteRob

    PeteRob Well-Known Member

    Save one as uncompressed as you can (max quality) and check the calculation. Lightroom gives tbe pixel size though you may have to toggle the display options to show it.
  10. AlanW

    AlanW Well-Known Member

    DJ72, there'a a small utility which checks the file size, written by an Alamy contributor, which you might find useful - you'll find it here, just point it at the folder where you have the jpegs you want to upload to Alamy.

    I assume you want to sell you pictures rather than just "make them available to a wider audience", in which case, unless you're in for the longterm and plan to build up a portfolio of several thousand (diverse) images that are well keyworded then you're probably wasting your time.

    It might be worth hanging out at the Alamy Forums for a while to get a better idea about what you could be letting yourself in for!

    Good Luck

  11. DJ72

    DJ72 Member

    Hi Alan. Thank you very much for posting the link to that size calculator. I did see it yesterday but wasnt sure about it. Thanks for recommending, i will download later today.
    Honestly, my intention with Alamy is to see if my photographs are of a certain grade and yes, to get a wider audience. As far as making money I'm not sure if it will be more than a few quid anyway so under no monetary aspirations.

    Thanks again,
    AlanW likes this.

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