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Files exported as png increase in size?

1005 Views 14 Replies Latest reply: May 12, 2012 10:29 AM by rshammaa RSS
rshammaa Level 1 Level 1 (0 points)
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May 4, 2012 9:11 PM

Hi guys,

 

I have a Panasonic Lumix GH1 with a 14 MP sensor outputting 12-MP RW2 files. I exported them from Aperture 3 Library as original size png's to my desktop. When I clicked on them to check them out, most of them were much larger (up to 21 MP), and some even shrank.

 

Does that mean I can blow these up larger than I could as jpg's?

 

Can anyone figure it out? What happened there? I just changed the file format on them, that's all.

 

Thanks a lot,

 

Raphael

iMac 21.5", Mac OS X (10.7.2), Pages for iPhone/iPad
  • Terence Devlin Level 10 Level 10 (121,670 points)
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    May 4, 2012 11:16 PM (in response to rshammaa)

    1. MP - mega pixels - has no little bearing on the size of the file. It's a measure of how many pixels are on the camera sensor. Megabytes (MB) are a measure of file size.

     

    2. Original size in Aperture refers to the dimensions of the image - length by breadth, not file size.

     

    3. Changing format will always produce a different file size. Each different format - tiff, png, jpeg etc - all carry their data load in different ways.

     

    4. No you can't blow these up larger than Jpegs. You can't add pixels with Aperture.

     

    Regards

     

     

    TD

  • léonie Level 8 Level 8 (46,455 points)
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    May 5, 2012 12:19 AM (in response to Terence Devlin)

    4. No you can't blow these up larger than Jpegs. You can't add pixels with Aperture.

    Are you sure? Never say "no", TD; I am doing just that all the time   Try this:

    • Edit a custom export preset and set the "Size To:" as "Fit within (Pixels).You can specify "Width:" and "Height:" to much larger values then the original image dimensions.

     

    I just enlarged a tiny 677x420 image (87 KB)  to 3000x1861 pixels and 2.9 MB.

    I discovered that when I needed testdata of a certain pixel size.

     

     

    Cheers

    Léonie

  • léonie Level 8 Level 8 (46,455 points)
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    May 5, 2012 12:24 AM (in response to léonie)

    Larger.png

  • léonie Level 8 Level 8 (46,455 points)
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    May 5, 2012 12:27 AM (in response to léonie)

    croc.png

  • Terence Devlin Level 10 Level 10 (121,670 points)
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    May 5, 2012 4:14 AM (in response to léonie)

    Dead right.. but how was the quality?

     

    Regards

     

     

    TD

  • léonie Level 8 Level 8 (46,455 points)
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    May 5, 2012 7:13 AM (in response to Terence Devlin)

    Dead right.. but how was the quality?

    You don't really have to ask, do you?

    Blurry - as horrible as is to be expected when you simply enlarge the number of pixels by a factor of 12, without adding any new information - a waste of storage and not to be recommended. As I said, I simply needed a large image file with a fixed numbers of pixels for testing.

     

    Regards

    Léonie

    Australien-Krokodilblownup.jpg

  • léonie Level 8 Level 8 (46,455 points)
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    May 6, 2012 12:45 PM (in response to rshammaa)

    The MB informs us of file size-  "digital" file size, and the MP informs us as to how that amount of info is being distributed 2-dimentionally. Correct?

    You got it - nearly.

     

    The MB informs us of file size-  "digital" file size

     

    What exactly can be inferred from the filesize? The filesize will depend on the resolution (pixelsize) and on the compression scheme.

    • Any lossless format (tiff, png, raw, psd) will result in large filesizes, in especially when set to 16 bit.
    • Lossy compression (jpeg) only approximates the image and will degrade the image, but will reduce the file size depending on the setting of the quality slider.

     

    So, how large of a high quality print can I hope for at 12MB per image?

    That is easier to answer for 10 MP - a simple piece of arithmetic:

     

    For example, my Lumix FZ28 raws have a dimension of 3652 × 2738 (10.0 MP)

     

    If I print it at 300 dpi (dots per inch) the width will be: 3652 points / 300 dpi

         = 12.2 inches x 9.12 inches

     

    If I print it at 200 dpi (dots per inch) the width will be: 3652 points / 300 dpi

         = 18.26 inches x 13.69 inches

     

    If the compression is lossless (tiff, png, raw) printing at this size will give a very good quality, but if you have a jpeg format with low quality stting, the print might show artefacts and be blurry.

     

    Regards

    Léonie

  • léonie Level 8 Level 8 (46,455 points)
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    May 9, 2012 9:34 AM (in response to rshammaa)

    You are welcome!

     

    Léonie

  • léonie Level 8 Level 8 (46,455 points)
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    May 11, 2012 8:35 AM (in response to rshammaa)

    Larger sensor and larger file size are not necessarily the same - so I am not quite sure what you are asking.

     

    The image quality is determined by the spatial resolution and the photometric resolution (I'll ignore the quality of the lens for now and talk only about the sensor).

     

    • The spatial resolution depends on the number of pixels the sensor will sample from the image.
    • The photometric resolution will depend on the signal to noise ratio, and that will depend on the size of each cell in the sensor. A large sensor will have a better signal to noise ratio than a smaller sensor of the same pixel size. If you compare sensors don't look at the pixel size but at the dimensions of the sensor.

     

    The signal to noise ratio is important, if you need a long exposure because of insufficient light, e.g. time at dawn or dusk.

     

    Does one get a better print from a larger file of the same exact subject?

     

    To produce the print at the correct size the image will have to be subsampled. If you print from Aperture then Aperture will do that perfectly. I do not know what kind of subsampling the print service will use that you send your images to. But it should suffice to send a high quality image with exact the pixelsize you need.

     

    Regards

    Léonie

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